Programme pour l'environnement des Caraïbes
Programme des Nations Unies pour l' environnement
Ecosystem and Socioeconomic Response to Future Climatic
Conditions in the Marine and Coastal Regions of the
Caribbean Sea, Gulf of Mexico, Bahamas, and the Northeast
Coast of South America
[Prepared by: George A. Maul, Chairman
UNEP/IOC Task Team
on Implications of Climatic Changes in the Wider Caribbean Region.]
Rapport technique du PEC No. 22
1993
TABLE OF CONTENTS
LIST OF FIGURES ............................................................................................................................................................... ii
LIST OF TABLES ................................................................................................................................................................. ii
ABSTRACT .......................................................................................................................................................................... 1
INTRODUCTION................................................................................................................................................................... 1
TERMS OF REFERENCE .................................................................................................................................................... 6
Temperature Rise of 1.5°C by 2025................................................................................................................7
Sea Level Rise of 20 cm by 2025..................................................................................................................10
EFFECTS OF SEA LEVEL CHANGES ON COASTAL ECOSYSTEMS .......................................................................... 10
Deltas ............................................................................................................................................................11
Estuaries .......................................................................................................................................................11
Coral Reefs ...................................................................................................................................................12
Mangroves.....................................................................................................................................................12
Seagrass Beds ..............................................................................................................................................12
Fisheries........................................................................................................................................................12
EFFECTS OF TEMPERATURE ELEVATIONS ON ECOSYSTEMS ................................................................................ 14
Agricultural Resources ..................................................................................................................................15
Coastal Systems............................................................................................................................................16
Fisheries........................................................................................................................................................16
POSSIBLE SOCIOECONOMIC CHANGES ...................................................................................................................... 16
Agriculture and Forestry ................................................................................................................................17
Fisheries and Coastal Zones.........................................................................................................................17
Settlements and Structures ...........................................................................................................................18
Public Health .................................................................................................................................................19
MOST VULNERABLE AREAS OR SYSTEMS.................................................................................................................. 20
Physical Processes .......................................................................................................................................20
Ecological Aspects ........................................................................................................................................20
Socioeconomic Issues...................................................................................................................................21
Synthesis.......................................................................................................................................................21
MODELLING....................................................................................................................................................................... 21
Numerical and Scenario Models of Climate Change.....................................................................................21
Numerical Models of Climatic Change Socioeconomic Impact .....................................................................26
CONCLUSION .................................................................................................................................................................... 28
ACKNOWLEDGEMENTS .................................................................................................................................................. 33
REFERENCES.................................................................................................................................................................... 33
APPENDIX: GLOSSARY AND ABBREVIATIONS ........................................................................................................... 36
CEP Technical Report No. 22
LIST OF FIGURES
Figure 1. Reproduction of an early 18th century sea chart published by Gerard van Keulen..................................... 3
Figure 2. Schematic illustration of the components of the coupled atmosphere-ice-land-ocean climate system. . 4
Figure 3. October 1979 monthly mean pigment concentration field from CZCS satellite imagery............................ 5
Figure 4. Temperature change for the last 10,000 years and 1,000 years based on records in Europe (upper two
panels; redrawn from IPCC (1990a) and NAS (1975), respectively), and a global estimate (lower panel; from
Hansen and Lebedeff, 1988). ............................................................................................................................................. 8
Figure 5. Sea level change based on geological records taken in south Florida ........................................................ 9
Figure 6. Satellite infrared image of Hurricane Gilbert observed at 13 September 1988 by the Geostationary
Operational Environmental Satellite (GOES-7). ............................................................................................................. 15
Figure 7. Pathways in socioeconomic aspects of the climate change problem ........................................................ 18
Figure 8. Pathways by which C02-induced climate change may affect human health (from de Sylva, 1993). ....... 19
Figure 9a. Annual average temperature change due to effective CO2 doubling from GCMs ................................... 24
Figure 9b. Annual average precipitation change due to effective C02 doubling from GCMs .................................. 25
Figure 10. Paleoclimate and greenhouse model comparisons of the meridional profile of seasonal average
surface temperature in the Northern Hemisphere......................................................................................................... 26
Figure 11. Global temperature (upper curves) and sea level (lower curves) projections for the various IPCC 1992
scenarios............................................................................................................................................................................ 29
Figure 12. Schematic of the two-level PC-based socioeconomic numerical model.................................................. 30
Figure 13. Photograph of a typical C-MAN station ........................................................................................................ 32
LIST OF TABLES
Table 1. Terms of Reference .............................................................................................................................................. 7
Table 2. Implications of Climatic Changes in the Intra-Americas Sea ........................................................................ 22
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Ecosystem and Socioeconomic Response to Future Climatic Conditions in the Marine and Coastal
Regions of the Caribbean Sea, Gulf of Mexico, Bahamas, and the Northeast Coast of South
America
ABSTRACT
Global climate change, and particularly the impact of human activities on Earth's biogeographical
environment, is of enormous socioeconomic and ecological importance. It is the regional effect of global
change, however, that weighs most heavily on individual lives because of the complexity of local
response to a world-wide phenomenon. This report summarizes the opinion of a Task Team of 23 experts
concerning the implications of climate change in the Intra-Americas Sea (Gulf of Mexico - Caribbean Sea
-Bahamas - Bermuda - Guianas), of a global 1.5°C temperature and 20 cm sea level rise by the year
2025. For some ecosystems in the region, the effect of temperature rise is much more important than sea
level rise, and vice versa for others; for some neither is important; for others both are important. Of the 14
ecosystems considered, the most heavily impacted are expected to be deltas and beaches, both because
of sea level rise; neither are particularly vulnerable to a modest temperature rise. Estuaries, wetlands,
lagoons and seagrass beds will all be moderately affected by both the 1.5°C and 20 cm scenarios. The
other two very important ecosystems, mangroves and coral reefs, are expected to have a low-
to-moderate vulnerability to climate change per se, but both are expected to experience extreme stress
due to local anthropogenic activities such as deforestation, coastal development, runoff, overfishing, and
tourism. Seven socioeconomic issues were also studied in the context of local response to global change;
tourism and the influence of tropical storms are considered most important vis a vis levels of vulnerability.
As with the ecosystems, some other socioeconomic issues are more affected by sea level rise (e.g.,
settlements and structures, and cultural heritage) than temperature rise (which mostly affects coastal
zones, public health, and human migration). In addition to evaluating the effects of 1.5°C and 20 cm
global rises, the Task Team discussed the potential local rates of temperature and sea level rise and
found that for the Intra-Americas Sea, less climatic change is expected than for other areas of Earth, but
that human population pressure will significantly stress the region's environment. Finally, we report on
new computer-based decision-making tools for evaluating the effects of climatic change, tools that will
give decision makers quantitative information upon which to base new policies for management.
INTRODUCTION
The history of modern civilization is inexorably related to Earth's climate. Climatic changes have
influenced our literature, raised and toppled empires, altered our religious views, modified economies,
forced mass migrations of both humans and animals, caused hunger and starvation; the list is nearly
endless (e.g., Bryson and Murray, 1977; Lamb, 1982). Yet in the year of the quincentennial of the
European discovery of the Caribbean Sea (cf. Van Sertima, 1976, 1992 for discussions on African and
Chinese visits ca. 1000 B.C.), precious little more is known about climate in the region than what the
early European explorers told their sponsors. Assessing the impact of climate change then becomes a
particularly challenging problem.
The area of concern encompasses the marginal or semi-enclosed seas of the tropical and
subtropical western North Atlantic Ocean: the Caribbean Sea, the northeast coast of South America
(excluding Brazil), the Gulf of Mexico, the Bahamas, and (biogeographic ally) Bermuda. This area is
called the "Wider Caribbean Region" by the United Nations Environment Programme (UNEP) and is also
called the "Caribbean Sea and Adjacent Regions" by the Intergovernmental Oceanographic Commission
(IOC) of UNESCO and its Subcommission IOCARIBE. Early oceanographers mistakenly called it the
"American Mediterranean," but the author prefers the term "Intra-Americas Sea" to emphasize its unique
and interrelated geography, climate, and culture.
This study emphasizes the marine and coastal environment and addresses the implications of
climatic change in the Intra-Americas Sea and its environs. To facilitate understanding the technical terms
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CEP Technical Report No. 22
of this report, a glossary (abbreviated from Maul and Baig, 1993) is included as an appendix. As was the
perspective of the early European and African explorers, the report is limited to a sailor's view of the
coastline, reefs, passages, harbors, deltas, estuaries, and deep waters of this semi-enclosed sea (Figure
1). Nevertheless, such a perspective presents a formidable challenge involving meteorology,
oceanography, geology, economics, sociology, medicine, law and ecology.
To address such challenges, UNEP was founded in 1972, and within two years established its
Regional Seas Programme. An action plan for the Caribbean Environment Programme was adopted in
198 1, and five years later the Regional Coordinating Unit (RCU), in consultation with the IOC and
IOCARIBE, began addressing marine environmental issues from the RCU's new offices in Kingston,
Jamaica. In concert with the recommendations of the World Meteorological Organization
(WMO)/International Council of Scientific Unions (ICSU)/UNEP-sponsored 1985 meeting in Villach,
Austria (WMO/ICSU/UNEP, 1986), the RCU extended its marine environmental interests to include
questioning the impact of climate change in the region (UNEP, 1987). Similar programmes are active in
five other marginal seas under the Regional Seas Programme.
Climate in marginal seas such as the Intra-Americas Sea is linked to the global system by the air
and water that flows over or through the region. The global system is driven by incoming solar radiation
and outgoing Earth radiation; Figure 2 is a sketch of the radiative balance and the interactions with
components of the system. The role of the air and ocean is to distribute the heat received from the sun,
principally from the warm equatorial regions where there is an excess of heat to the poles where there is
a deficit. Warm ocean surface currents pass through the Intra-Americas Sea, eventually loosing heat to
the atmosphere as they travel toward Europe where they sink and return as deep water flowing into the
South Atlantic at about 1500-4500 m depth along the eastern margin of the Bahamas and Caribbean
Sea. Figure 2 also shows some of the principal mechanisms involved in the global system such as solar
radiation, clouds, greenhouse gases (principally H2O water vapor, and CO2, carbon dioxide), ice,
volcanos, river runoff, land type (forests, deserts, cultivation, etc.), and the thermodynamic effects of heat
exchange between water, land, ice, and the atmosphere. Human intervention enters the global system
through increasing the amount of greenhouse gases (mostly through the respiration of civilization, i.e. C02
production, methane, and CFC's) changing of land features (i.e. deforestation, construction, agriculture),
and affecting the quantity and quality of riverine inputs.
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Figure 1. Reproduction of an early 18th century sea chart published by Gerard van Keulen.
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Figure 2. Schematic illustration of the components of the coupled
atmosphere-ice-land-ocean climate system.
See Appendix for definitions of the chemical symbols and other terms. In addition to natural
variability in the components of the climate system (atmosphere, hydrosphere, cryosphere,
geosphere, and biosphere), human activity is both directly and indirectly causing complex
additional variability. From Berger and Labeyrie (1987).
Although in a regional sense each of the factors illustrated in Figure 2 are operative, it is locally
where the anthropogenic effects are most noticeable. For semantic reasons it might be better to think of
climate change as a global phenomenon with regional implications, and to think of environmental change
as a regional issue with global implications. It is at the regional and local level that human activities are
most identifiable and approachable in terms of effecting meaningful immediate change. For example, the
surface waters of the Intra-Americas Sea carry heat from the South Atlantic Ocean to Europe through the
Caribbean Current, the Yucatan Current, the (Gulf of Mexico) Loop Current, the Florida Current, and the
Gulf Stream; the same waters carry pesticides, tarballs, flotsam and jetsam that wash up on the beaches
of the region that are so important to our tourism industry. So, while understanding the role of our oceanic
waters is crucial to predicting Earth's climate, it is the influences of those same waters that affect our local
economy and the health of many marine industries.
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The Intra-Americas Sea is unique in that it is the genesis of a western boundary current, the Gulf
Stream System. On the other hand it is similar to other marginal seas such as the Mediterranean Sea in
that it is strongly influenced by rivers. Figure 3 (from Müller-Karger, 1993) is a composite of satellite-
derived ocean surface pigment concentrations, that shows the interaction of the five largest rivers (the
Amazon, the Orinoco, the Magdalena, the Rio Grande, and the Mississippi) plus the myriad of smaller
rivers, and the ocean currents. Off the Amazon, the river waters can be seen to turn clockwise and advect
towards Africa in the North Equatorial Counter Current: Orinoco River water can be traced across the
eastern Caribbean Sea all the way to Puerto Rico and Hispaniola; a plume of the Mississippi River can be
observed almost to the Florida Keys (it has been studied as far north as the Carolinas at other times); a
large Loop Current eddy is seen south of the Rio Grande carrying its waters into the western Gulf of
Mexico. The interaction of our rivers with these very strong oceanic currents is quite unique in the world
ocean, and is of special interest in the context of the health of the marine environment. If there are
changes in the local climate, the rivers will be affected.
Figure 3. October 1979 monthly mean pigment concentration field from CZCS satellite
imagery.
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Original color coded figure showed warm colors (yellow, orange, and red) representing high
pigment concentration or other colored material in river plumes and shallow water, and cooler
shades (purple, blue, and green) representing low concentrations; black in the original color plate
represented no data, due either to cloud cover or lack of coverage; brown in the original
represented land. Rivers that affect the region have been outlined using World Database 11 files.
From Müller-Karger (1993).
There is little doubt however that global climate is changing, but there is an important difference in
the climate change that is now understood to be taking place: human activity may be involved. The
effects of such anthropogenic activity on the region are difficult to isolate from other natural oscillations in
Earth's climate. Nevertheless, the arguments are accepted that regional climatic scenarios (Lamb, 1987)
are valuable, with the understanding that they are not a prediction of future climate but an internally
consistent view of a plausible climatic future. However, with the influence of human activity, there is even
more uncertainty in developing climatic scenarios, and clearly a great deal of scientific research is still
necessary. It is with these caveats, like the sailors who made records 500 years ago, that we explore the
uncharted seas of the implications of climate change.
TERMS OF REFERENCE
Each Task Team involved in the UNEP Regional Seas Programme has used a common format in
assessing the implications of climate change. The common format is called the Terms of Reference,
developed at the 1985 WMO/ICSU/UNEP meeting in Villach, Austria (see Table 1). At Villach, an
equilibrium global warming of 1.5-4.5°C and a global sea level rise of 20-140 cm was forecast based on
an expected doubling of the greenhouse gases between the beginning of the Industrial Revolution and
the year 2030. The determinations to be made by each Task Team involve a common scenario, and
although not specified in the Terms of Reference, the Task Team for the Wider Caribbean Region chose
to question separately the validity of the scenario as it applies to the local marine and coastal
environment.
Many climate change scenarios have been made, as a quick reading of the references in Lamb
(1987) and others will show. For this UNEP/IOC study, a rise in temperature of 1.5°C and a rise in sea
level of 20 cm by the year 2025 (WMO/ICSU/UNEP, 1986) is the baseline scenario. The lower values are
chosen because by 2025 it is not expected that climatic equilibrium to C02 doubling will have been
reached due to the thermal inertia of the oceans (IPCC, 1990a). Deliberations by the Task Team
emphasized the point that 1.5°C and 20 cm are a global change scenario, which is interpreted to mean a
global average change, that may or may not be realistic for the Intra-Americas Sea. While the Task Team
used these baseline values in addressing the implications, one report (Hanson and Maul, 1993) asks
"Does the historical record support such predictions for the region?"; the answer is ambiguous.
Since 1985, projections of future climate have been hotly debated in the scientific literature and
(sometimes unfortunately) in the popular press as well. In an effort to bring about a scientific consensus,
UNEP and the WMO co-sponsored the Intergovernmental Panel on Climate Change (IPCC). The "best"
IPCC (1990) estimate is that by the year 2100, sea level will rise 50 cm, with a "high" estimate of 100 cm.
The conclusions of the Second World Climate Conference (Geneva, 1990) are that "global warming is
predicted to reach 2°C to PC over the next century... accompanied by sea level rise of 65 ± 35 cm by the
end of the next century". These are not contradictory statements, but clearly the issue continues to be
debated (Maul, 1992), and requires close attention by scientists and administrators alike.
The last issue in interpreting the Terms of Reference is defining how the Task Team understands
the terms "climate" and "climate change" (q.v., Appendix). Climate is understood to be limited to the time
averaged meteorological and oceanographic conditions of the marine and coastal environment in the
Intra-Americas Sea; although agriculture and forestry are briefly discussed, they are only considered in
their relation to the ocean. Climate change is understood to mean the decadal-scale scenario of a 1.5°C
temperature rise and a 20 cm sea level rise; short time scales, such as seasonal and high frequency
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aspects of interannual change, are not considered, although certain aspects of El Niño-Southern
Oscillation (ENSO) events are explored.
Table 1. Terms of Reference
The study covers the marine environment and the adjacent coastal areas influenced by or influencing the
marine environment. The terms of reference of the study are:
·
to examine the possible effects of sea level changes on the coastal ecosystems (deltas, estuaries,
wetlands, coastal plains, coral reefs, mangroves, etc.);
·
to examine the possible effects of temperature elevations on the terrestrial and aquatic
ecosystems, including possible effects on economically important species;
·
to examine the possible effects of climatic, physiographic and ecological changes on the
socioeconomic structure and activities;
·
to determine areas or systems most vulnerable to the above changes; and
·
to prepare a comprehensive, well-documented report reflecting the points above.
This and other studies are based on: a) the best available existing knowledge about and insight into the
problems relevant to the subject of the study; b) assumptions accepted at the International Conference in
Villach, 9-15 October 1985 with the understanding that these estimates will be revised on the basis of regional
scenarios yet to be developed); and c) several detailed case studies, which constitute in part, the material used
to prepare this summary.
Temperature Rise of 1.5°C by 2025
Climatologists use a variety of means to describe Earth's past climate. In the U.S. National
Academy of Science report Understanding Climatic Change (NAS, 1975), a wealth of information is given
on the subject. To illustrate current knowledge about temperature change, temperature records for the
last 10,000 and 1,000 years (Figure 4), show that Earth's temperatures have varied significantly since the
fifteenth century European "discoveries" of North America. In fact, when the Caribbean Sea was
discovered, Europe was in a cold period known as the Little Ice Age. At present, Earth's climate is
warmer than it has been in the last 1,000 years, but by no means is it as warm as it was in several past
epochs, as the longer records (last 1,000,000 years) indicate. So while an interpretation of the last 100
years shows increasing global temperatures on average (Hansen and Lebedeff, 1988; lower panel in
Figure 4), the decades of 1940-1970 had declining temperatures. Translating the global records such as
shown in Figure 4 to the regional level was one important challenge for the Task Team.
Fortunately, geochemists are constructing climatic histories of the Intra-Americas Sea region, and
are showing that much of the variability shown in the upper panel of Figure 4 applies to the Caribbean
Sea and Gulf of Mexico. Hodell et al. (1991) published a 10,000-year history of oxygen isotope (18O)
measurements taken from Lake Miragoane, Haiti (not shown), which has many of the characteristics of
this "global" temperature curve; most especially they conclude that 18O roughly follows the Milankovitch
orbitally induced insolation curve. But they note that superimposed on the orbitally forced climate trend
(cooling for the next 5,000 years) are abrupt events resulting from non-linear ocean-atmosphere
interactions. So while the Task Team debated the "historical record" (last ~150 years), they were
cognizant of the progress and uncertainties in applying global-change arguments to a specific region.
Does the historical record support the 1985 WMO/ICSU/UNEP scenario of a 1.5°C temperature
rise in the region by the year 2025? Data to assess a rise of sea surface temperature were considered
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scarce, so Hanson and Maul (1993) decided to analyze air temperature at Key West, Florida. The 136
year record gives evidence that a warming has occurred between 1890-1950, but the last 30 years or so
have been relatively steady at +0.3°C above the long-term mean; a similar analysis of air temperature
from ship reports in the Straits of Florida shows no deviation from constancy of the mean. Gray (1993)
found that the maximum air temperatures in Jamaica and in Trinidad and Tobago increased during the
last 10 years, but that evaporation had decreased (which is inconsistent with a temperature increase); it is
unclear if these changes are due to climatic change or to other factors. Aparicio (1993), based on records
from 1951-1986, reports an air temperature trend of +0.1°C /decade in Venezuela. Linear extrapolation of
these case studies leads one to see some suggestion of an air temperature rise in the region, but that
1.5°C seems to be too high; less than LOT rise by 2025 appears to be a more plausible picture of our
future temperature.
Figure 4. Temperature change for the last 10,000 years and 1,000 years based on records in
Europe (upper two panels; redrawn from IPCC (1990a) and NAS (1975), respectively), and
a global estimate (lower panel; from Hansen and Lebedeff, 1988).
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Temperature scale for the upper two panels is only approximate and is chosen to be in agreement
with the record for the last 100 years which is based on direct observations. Maul (1992)
discusses urbanization effects in Hansen and Lebedeff (1988) and gives references related to the
issue (cf. Wigley and Santer, 1993; Gallegos et at., 1993).
Figure 5. Sea level change based on geological records taken in south Florida
by Wanless et al., 1988, and from Jamaica by Digerfeldt and Hendry, 1987. The relative rise of 30
cm per 100 years shown in the inset is based on direct observations at all PSMSL (Pugh et al.,
1987) RLR sea level stations in the region; dots show range of standard error of the mean. Panel
in lower right shows range of linear trends for PSMSL RLR records ³ 19 years long (from Hanson
and Maul, 1993).
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CEP Technical Report No. 22
Sea Level Rise of 20 cm by 2025
As with questioning the validity of the global temperature change for the region, the Task Team
looked into the historical sea level record to put the WMO/ICSU/UNEP (1986) scenario into perspective.
The remarkably slow rate of sea level rise in South Florida and in Jamaica during the last 3,200 years
(only about 0.04 cm/yr; Figure 5; cf. Hendry, 1993) allowed many shorelines to stabilize or to expand, and
many shallow marine environments to build. However, since the early 1930's, sea level records from
many sites around Florida show much faster rates of sea level rise, very similar to the rate during the
period 3,200-5,500 years ago, when there was a rapid retreat of the shoreline. The data in Figure 5 gave
the Task Team a benchmark against which to judge the WMO/ICSU/UNEP global scenario of 50 cm rise
per 100 years.
Does the modem historical record of the Intra-Americas Sea support the WMO/ICSU/UNEP (1986)
scenario of a 20 cm sea level rise by the year 2025? To answer this question, the highest quality (revised
local reference) data on file with the Permanent Service for Mean Sea Level (PSMSL) were studied by
Hanson and Maul (1993) and Hendry (1993) for the Intra-Americas Sea, and from Venezuelan records by
Aparicio (1993) for the southern Caribbean Sea. For the longest records, Hanson and Maul found that
sea level is rising on average at about 0.36 cm/yr (±0.25 cm./yr) over the last 30 years, but due to
complicated tectonic activity, subsidence, and petroleum/groundwater extraction, the values ranged from
+1.0 cm/yr in Texas (rising sea level) to -0.3 cm/yr in Mexico (falling sea level). At Key West, Florida, a
site of tectonic stability, the rise is 0.22 cm/yr (±0.01 cm/yr), based on the years 1913-1986. More
important perhaps, is that sea level rise due to temperature/salinity changes in the upper 1,000 m of the
water column east of Abaco Island (Bahamas) for 1950-1987 was +0.14 cm/yr, and there is no evidence
of acceleration in the rate of rise. So, as with the temperature scenario, a lower value, perhaps 10 cm. by
2025, may be a more plausible regional value, but the high spatial variability makes a regional average
nearly meaningless; site specific values are required for realistic assessments.
Gallegos et al. (1993) and Mercado et al. (1993) cautiously advise that many more long records are
required in order to sort out the decadal and longer wave motions in the relative sea level record. The
physics of the very lowest frequencies in oceanic circulation are not well understood. Circulation, the
three dimensional movement of water with time, is affected by geological activity, the wind field, Rossby
waves, behaviour of the Sverdrup balance, interbasin modes of oscillation, and so forth. Progress in
numerical modelling will give the resolution to determine submesoscale features and subdecadal
oscillations, but it may be 10 years before such calculations are possible. To further complicate the issue,
Chao (1991) argues that sea level should have fallen by about 7 cm in the last 100 years due to the
building of reservoirs for irrigation and water control (humankind is building more than 500 15-m high
dams per year). In the interim, thoughtful extrapolation of the PSMSL observations, in concert with a
vigorous modelling activity, will give the most plausible estimates of future sea level.
EFFECTS OF SEA LEVEL CHANGES ON COASTAL ECOSYSTEMS
The first task in the Terms of Reference (q.v., Table 1) is to examine the possible effects of sea
level changes on the coastal ecosystems. Gable (1993) gives an overview of the ecosystems in the
region, and Oceanus (1987/1988) is an issue devoted to Caribbean marine science. The variable of
interest in this section is relative sea level (RSL) rise, that is the net effect of tectonic uplift or subsidence
plus expansion or contraction of the water column. During the Holocene (last 10,000 years) in Jamaica
for example (Hendry, 1993), sea level rise is less than the 0.5 cm/yr implied by the assumptions at the
1985 International Conference in Villach, and in the last 3,000 years RSL rise has been almost nil (q.v.,
Figure 5). All other factors being equal, 0.5 cm/yr (20 cm between 1985 and 2025) is a very rapid rise
and is expected to place an unusual stress on coastal ecosystems.
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Deltas
In the region there are four major river deltas: the Mississippi (USA), the Rio Grande (Mexico/USA),
the Magdalena (Colombia) and the Orinoco (Venezuela); q.v., Figure 3. Deltas (Müller-Karger, 1993), are
particularly vulnerable to erosion enhanced by sea level rise because the sediments are unconsolidated
muds subject to subsidence and compaction. One might expect, according to the Bruun Rule, a shoreline
retreat up to several meters horizontally for each centimeter RSL rise; this translates into thousands of
hectares of lost land. The problem is exacerbated by potential increased tropical storm activity (Gray,
1993), since most shoreline erosion occurs during storms, and by subsidence such as in the case of
Louisiana. However, Mercado et al. (1993) argue that the 20 cm RSL rise scenario will be of no practical
consequence on storm surge models (such as SLOSH; cf. Mercado et al., 1993), as far as it might
introduce increased surge heights. Delta benthic systems would be most affected or destroyed by the
expected RSL rise. In contradistinction, RSL near the Orinoco Delta may be falling, but more
measurements are needed to document this preliminary result.
Estuaries
The RSL effect on estuaries, as with deltas and many other geomorphological features, must be
considered on a case-by-case basis in order to make meaningful impact assessments in the region
(Vicente et al., 1993). Because of local uplift, the following areas are expected to have reduced increase
in RSL due to climate change: east coasts of the Cayman Islands; north coast of Jamaica; southeast
coast of Cuba; north coast of Bahia, the southwest coast of Haiti; Barbados; north coast of the Dominican
Republic; and the southwestern Gulf of Mexico. In addition to the subsidence experienced in deltas, other
areas experiencing downwarping include: the Maracaibo region of Venezuela; the entire northern Gulf of
Mexico from Texas to Florida; the estuary of Port au Prince; and the western Gulf of Honduras. Coastal
lagoons, salinas and estuaries, depending on their location, all could suffer from saline intrusion, but
lagoons should be able to support their usual nurseries; salinas on the other hand (Vicente et al., 1993),
could be flooded over continuously and lose their economic value.
Wetlands
The ability of wetlands to sustain vertical growth is a balance between sedimentation and RSL rise.
In the tectonically complicated Intra-Americas Sea, no single definitive statement is possible, but in the
last 5,000 years, many wetlands have been able to keep pace with rising sea level. In areas with marked
subsidence, particularly if there is canalization of organic silts and clays away from the wetlands into the
marine environment (Hendry, 1993), wetlands will be submerged and lost to productivity. Where wetlands
are bounded by steep-sided basins, as is the case in many of the Caribbean islands, it is unlikely that
they will be replaced as sea level rises; on gentler island and continental floodplains, such as the northern
Gulf of Mexico, the problem may be less severe. Loss of some wetlands economies such as shellfish
industries is expected to occur with the 20 cm RSL rise scenario (Snedaker, 1993).
Coastal Plains
The primary effect on coastal plains will be increased flooding during storms (from raised sea level
and/or from heavy rainfall). Unfortunately many storm surge models differ markedly in their predictions
(the variability in their predictions being several orders of magnitude larger than the 20 cm scenario;
Mercado et al., 1993). Shore migration (both erosion and accretion) will vary depending on the substrate,
and sandy beaches will be more affected than rocky coasts. No single rule can be applied for the region
as a whole, but modelling on a local scale is required to account for differences such as tectonic
displacement, beach structure, offshore bottom topography, and storm frequency and magnitude. The
concentration of human population in the poorly drained low-lying coastal plains is a source of concern in
many countries. Special attention should be paid to areas where subsidence is evident, as it will
exacerbate the flooding problem. Port au Prince, Haiti, Puerto Cortes, Honduras and the
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CEP Technical Report No. 22
Galveston-centred area of the U.S. Texas-Louisiana coast, are coastal plains areas most vulnerable to
flooding from sea level rise and storms.
Coral Reefs
The second largest coral reef system in the world dominates the offshore area of the western
Caribbean Sea (Milliman, 1993), and all but the northern Gulf coast have extensive reef systems. Growth
of individual coral organisms is estimated between 1-20 cm/yr (Vicente et al., 1993), and reef growth
rates as a whole are known to be up to 1.5 cm/yr (Hendry, 1993). Not all reefs accumulate at these rates,
but if they did, they could keep pace with the rise in RSL of 20 cm by 2025 if other factors do not alter
growth conditions. Environmental stress on the reefs from other variables (storms, sedimentation,
disease, souvenir-hunting, rainfall, radiation, turbidity, overfishing, mass mortality in algal grazers, etc.)
may prevent some from keeping pace with rising RSL, resulting in alteration of the nearshore
hydrodynamics. The issue is further complicated by consideration of the type of reef, coastal
geomorphology, reef depth and ecological state of the reef in question. Accurate predictions on the effect
of RSL rise may be possible in reefs that have already been physically and biologically monitored, such
as in Panama, Jamaica, and Puerto Rico.
Mangroves
Mangrove forests are a unique feature of protected coastal shorelines of the tropics 'and
subtropics; their root systems (prop roots and pneumatophores) stabilize the sediment, dampen wave
energy, provide habitat shelter for numerous organisms, and form the base of the nearshore marine
foodweb (Vicente et al., 1993). The five species comprising the mangrove flora of the region occupy an
area of approximately 3.2 million hectares, or some 15% of the estimated world area of mangrove of 22
million hectares. Within the region, the best developed mangrove forests are associated with areas of
high precipitation and upstream land runoff. Because mangroves grow best in moderately saline
environments where the rate of peat production exceeds the anaerobic decomposition of peat by
seawater sulfate reducing microorganisms, it is postulated that mangroves can keep pace with RSL in
rainfed humid areas, but may be overstepped and abandoned in more arid areas particularly if inland
retreat is not possible. Thus, in terms of global climate change, future changes in patterns of precipitation
and catchment runoff may be more important than RSL (Snedaker, 1993). Notwithstanding the current
high rate of regional mangrove loss by overcutting, land clearing and habitat conversion suggests that
global climate change is a minor factor in considerations of the fate of this regionally important coastal
habitat.
Seagrass Beds
Seagrasses are a benthic environment throughout the region that are important in stabilizing
bottom sediments, serve as nurseries for juveniles, and providing surfaces upon which many organisms
attach. A 20 cm RSL rise per se is not expected to seriously affect the six common species (Vicente et
al., 1993), but if there are other changes, such as in the quality of light, influence of herbivores, substrate,
wave energy, or bottom slope, the beds may be impacted.
Fisheries
The impact of sea level rise on fisheries is not expected to be great unless turbidity increases due
to erosion from higher water or river runoff (Müller-Karger, 1993). Turbidity increase could have a
negative impact on fisheries particularly during the early life history stage (W. Richards, NOAA/NMFS,
pers. comm.). Estuarine dependent species in areas, such as Mississippi, the Florida Everglades,
Guyana and the Orinoco Delta, may be particularly vulnerable to sea level rise, especially if salinity
changes are involved. These ecosystems are also vulnerable to increases in the discharge by rivers of
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Response to Future Climatic Conditions...
pollutants, which may accumulate and eventually become harmful to humans and other animals in the
foodweb.
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EFFECTS OF TEMPERATURE ELEVATIONS ON ECOSYSTEMS
As discussed above, there is considerable question if trace gas-induced temperature elevation can
be seen in the records at Key West, Florida (U.S.A.), Venezuela, Jamaica or in Trinidad and Tobago.
Temperature change however is only one aspect of the meteorology that will effect terrestrial and aquatic
ecosystems. Hanson and Maul (1993) find no evidence for changes in precipitation at Key West during
the last 101 years; similarly, Aparicio (1993) finds none along the southern Caribbean. In the
Intra-Americas Sea, Gray (1993) finds decreased rainfall in the last 20 years, which he associates with
decreased hurricane activity. An increase of 1.5°C in sea surface temperature could increase the number
of hurricanes by as much as 4.0% (Gray, 1993), and the maximum wind speed by 8%; Shapiro (1982) is
quick to point out a considerable uncertainty in these numbers (40% increase means on average +1.6 ±
1.2 hurricanes/year). Many other factors are important in hurricane analysis, and it may be that the storm
formation location and track are more important than changes in strength or frequency.
Many people argue that recent major hurricanes such as Gilbert (Figure 6) in 1988, or Andrew in
1992, are examples of global warming causing more powerful storms. However, there is no scientific
evidence that increased sea surface temperatures (SST) are causing such storms, in fact the average
SST of the Caribbean Sea is steady (or perhaps slightly decreasing) over the last 40 years or so. Gray
(1993) shows that the number of tropical storms originating in the Caribbean Sea are fewer in number
during the last three decades than during the 1935-1955 period, and leaves open the question of whether
or not we are seeing natural cyclical changes in the storm patterns and strengths.
In the sense that Lamb (1987) develops climate change scenarios as plausible future events, Gray
argues for the following likely effects (cf. Gallegos et al., 1993; Aparicio, 1993):
·
rainfall will continue to decrease;
·
air temperatures will continue to rise;
·
surface wind speed will continue to increase; and
·
evaporation will increase.
Caution must be exercised in applying these changes as anything other than persistence forecasting. It is
unknown, for example, if the decreased frequency of large hurricanes over the last two decades is really
a long term trend or part of some cycle as yet not understood. Hurricanes are an important contributor of
rainfall; is the decrease in precipitation merely a reflection of fewer large storms? Increased temperature
may affect the drag of wind on water, but Mercado et al. (1993) and Hendry (1993) see no clear indication
of a significant change in storm surges or waves associated with elevated temperature. With these
thoughts in mind, the second item in the Terms of Reference (q.v., Table 1), "effects of temperature
elevation on the ecosystem, including on economically important species" is considered (cf. IPCC,
1990b).
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Response to Future Climatic Conditions...
Figure 6. Satellite infrared image of Hurricane Gilbert observed at 13 September 1988 by
the Geostationary Operational Environmental Satellite (GOES-7).
Hurricane Gilbert was the most intense Atlantic tropical storm on record, causing 318 deaths (202
in Mexico alone) and US$ 5,000,000,000 in estimated damages. At NOAA aircraft flight altitude
(10,000 feet or 3,000 m) the maximum wind gusts were 173 knots (89 m/s) and the central pressure
was 888 mb. Hurricane Andrew in 1992 caused US $20,000,000,000 in damage, far exceeding
Gilbert because it struck the heavily populated Miami, Florida area and then the southwestern
Louisiana region.
Agricultural Resources
Saline intrusion is expected to have more impact on agriculture in the coastal plains than elevated
temperature, particularly on rice production along the Guyana coast. Soil erosion probably will increase,
but poor management practices are probably more contributive than temperature elevation and saline
intrusion. Vicente et al. (1993) argue that it is unlikely that inland and hilly forests will be affected much by
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increased temperature, although Gray (1993) warns of increased erosion due to increased winds and
decreased precipitation. However, warmer temperatures could be a significant factor in forest fires,
particularly if precipitation decreases. Human settlements are unlikely to be affected significantly by 1.5°C
weather changes, except where RSL is important (Alm et al., 1993).
Coastal Systems
In the tropics, marine organisms live closer to their maximum thermal tolerance than those in more
temperate climates. Although the 1.5°C temperature rise scenario would raise the summertime mean
temperature to 30.5°C over much of the region, most migratory organisms are expected to be able to
tolerate such a change. Some corals will be affected (viz. the 1983 and 1987 bleaching events), but it is
expected that other environmental stresses will be more important (D'Elia et al., 1991; Milliman, 1993).
Littoral-supralittoral organisms, such as mangroves, are adapted to withstand high temperature, and
unless the 1.5°C increase affects the reproductive cycle, the temperature elevation will likely cause
unmeasurable results (Snedaker, 1993). Similarly, only seagrass beds located in thermal stress
situations already (i.e., in shallow lagoons or near power plant effluents) are expected to become
negatively affected by the projected WMO/ICSU/UNEP (1986) temperature rise.
Fisheries
The blue, clear waters of the region are relatively nutrient-poor, and most of the fisheries are
concentrated on Campeche Bank and along the northern coast of the Gulf of Mexico, at the Mosquito
Bank off Honduras and Nicaragua in the Caribbean Sea, and in the Gulf of Paria and the coastal waters
of the Atlantic Ocean off Suriname, Guyana and French Guiana (Gable, 1993). It is not expected that a
modest increase in temperature will significantly affect the fisheries except in some shallow lagoons
where hypersalinity may affect productivity, particularly if juveniles have a critical dependence on salinity
or temperature. Increased alongshore winds, however, could lead to increased coastal upwelling along
some continental coasts (Aparicio, 1993) or other oceanic circulation changes, (Gallegos et al., 1993)
and thus to increased productivity (cf. Vicente et al., 1993).
Tropical fish eggs hatch very quickly (12-48 hours), and development is associated with
temperature. Just as "cold snaps" can be devastating, so can "hot snaps," particularly during early
juvenile stages (W. Richards, NOAA/NMFS, pers. comm.). Extremes in temperature usually are averaged
out in climate analysis, but with increased temperature, the likelihood of "hot snaps" increases; the 1987
Caribbean coral bleaching event was attributed to "hot snaps" by some researchers (Milliman, 1993). The
complexities of the ecosystem could be greatly affected by slight temperature changes. It is unknown, for
example, why fish stocks either decline or increase by orders of magnitude, except due to early life
history events caused directly by the physical environment or indirectly through complex chains in
ecosystem dynamics. Temperature effects on tropical fisheries remains an important and unanswered
question, although there is some evidence of fish migration associated with increased coastal
temperatures.
POSSIBLE SOCIOECONOMIC CHANGES
Climate change will have socioeconomic impacts on both the micro-economic or localized level,
and on the macro-economic or economy-wide level (cf. IPCC, 1990c). The complexity of these
interactions is summarized in Figure 7, showing the numerous pathways possible in complex social
systems (cf. Alm et al., 1993; Engelen et al., 1993) and showing that the generic effect of human activity
is the strongly linear relation between human population and atmospheric C02 concentration (Idso,
1989). The smaller or the more coastal- oriented an economy is, the greater will be the impact of sea
level rise (Alm et al., 1993). The Intra-Americas Sea, with its many small island-based economies such
as fishing and/or tourism, is particularly vulnerable to the physical changes associated with changing
climate. Some climatic changes will benefit certain sectors of an economy (raising RSL may benefit the
construction industry), while being detrimental to others (beach erosion may cause a loss in tourism). A
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Response to Future Climatic Conditions...
climate change-induced benefit to the construction industry reflects a transfer of benefits and costs
rather than the creation of new benefits and costs. The net sum of costs and benefits must be assessed
on an individual basis because it is the true cost due to climate change only that is of interest (Engelen
et al., 1993).
Agriculture and Forestry
Islands usually have small, coastal aquifers, and sea-level rise will impact water quality in aquifers
that have hydrological continuity with the sea. Loss of agricultural land in low-lying coastal plains will be a
minor, but perceptible impact, particularly in those areas where saline intrusion affects the water supply,
such as on the leeward side of small mountainous islands; continental areas are not expected to be
seriously affected. Differing permeability in aquifers can cause great variability in the effect of rising RSL.
Relocation of wells, construction of weirs, water storage schemes and barging of water are all possible
socioeconomic responses. In regards to forestry, as noted in an earlier section, the expected climate
change impact is anticipated to be small compared to proper management policies on the industries and
people involved.
Fisheries and Coastal Zones
Most fishing in the coastal zone in the region is artisanal except for a few larger industries such as
the menhaden fishery in the Gulf of Mexico. The WMO/ICSU/UNEP (1986) scenario of 1.5°C and 20 cm
increases by 2025 AD are not expected to create any significant changes in the fisheries, although to the
artisanal fisherman, a displacement in traditional fishing sites may be perceived as being important (Alm
et al., 1993). There does remain an unanswered question of the effect on fisheries of extreme
temperature events. Aquaculture in the region as a whole is considered undeveloped at the present. The
critical issue of shoreline migration, which is the most important impact on the coastal zone, is discussed
in the following sections.
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CEP Technical Report No. 22
Figure 7. Pathways in socioeconomic aspects of the climate change problem
(from Alm et al., 1988; populations vs. CO, (1650-1990 AD) redrawn from Idso, 1989). The full
complexities are further discussed in Alm et al., 1993 and Engelen et al., 1993, but the interested
reader is also referred to IPCC (1990b) for impact assessments and IPCC (1990c) for response
strategies.
Tourism
The single most important industry in the region is tourism, especially in Florida, The Bahamas,
Cuba, Jamaica and the Lesser Antilles. Of all the possible climate change impacts that affect tourism,
none is so clearly demonstrated as beach erosion (q.v., Hendry, 1993). Shoreline migration will create
new areas of economic benefit as new beaches are built, but the protection, replenishment and
stabilization of existing beaches, at least until major existing tourist investments are amortized, represents
a principal socioeconomic impact. It is difficult to estimate the impact of climate induced sea level rise, in
addition to the erosion associated with the relentless interaction of the sea on the coast, that is not
associated with climate change; in addition, certain sand mining practices (such as in Trinidad and
Tobago) already are considered important. Indirect socioeconomic effects on tourism due to increasing
pollution, coral reef mortality and storm damage are also involved.
Settlements and Structures
Up to a certain point, structures will be worth building to protect settlements and facilities.
Navigation and port facilities normally have to be reconstructed and maintained, so the socioeconomic
impact of a 20 cm sea level rise is not considered serious (Alm et al., 1993). Some nearshore roads,
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Response to Future Climatic Conditions...
seawalls and bridges will have to be increasingly repaired, and if the RSL rise is augmented by increased
storm activity, the impacts will be serious, particularly in countries with marginal economies. As with
agriculture in low lying lands that depend on well water, many municipal water supplies and drainage and
sewage systems, will have to be modified; areas of particular concern in this regard are coastal cities of
Guyana and Belize (Vicente et al., 1993). The most damaging socioeconomic aspect is climate change
coupled with population growth and migration to coastal cities. Oftentimes the population growth is into
areas most likely to be impacted by water level changes, and in periods of extreme weather events,
serious public health impacts are probable in addition to physical danger (Hardin, 1971).
Public Health
Both temperature and sea level rises are expected to have an effect on human health; temperature
because many diseases and acute effects are associated with elevated temperatures, and with water
levels because water is a principal agent for many diseases and organisms that carry disease (Figure 8;
de Sylva, 1993). If higher temperatures are coupled with higher humidity as Gray (1993) expects, heat
related health stress and mortality will increase. Human health changes are related to a wide variety of
considerations including: mortality and morbidity related to weather and climate; extreme weather events;
airborne materials; seasonal diseases caused by microorganisms; parasitic diseases; nutrition; water
quality and abundance; and changes in the marine environment including population shifts in dangerous
fish, such as sharks, and toxic organisms (de Sylva, 1993). Socioeconomic effects relate not only to
increased spread of tropical diseases and their associated shift in costs and benefits to the health
industry, but also to potential losses in other industries due to health related absenteeism. It is anticipated
that transfer of costs and benefits will be associated with climatic change to public health in the region,
but that the health-care delivery systems will keep pace with the climate related aspects to the year 2025;
whether or not the systems are capable of coping with other social changes is uncertain.
Figure 8. Pathways by which C02-induced climate change may affect human health (from
de Sylva, 1993).
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CEP Technical Report No. 22
MOST VULNERABLE AREAS OR SYSTEMS
In order to determine areas or systems which appear to be most vulnerable to changes in sea level
and temperature (q.v., Terms of Reference, Table 1; cf. IPCC, 1990b), and their impact on ecological and
socioeconomic structures and activities, three broad topics are addressed: Physical Processes;
Ecological Aspects; and Socioeconomic Issues. Much of the material in the following sections is drawn
from notes and recommendations made during the deliberations of these three working groups of the
Task Team.
It was clear to the Task Team that detailed information on the wide variety of areas or systems
most vulnerable to climate change in the region could not be prepared without additional substantial effort
and support. In order to ultimately provide such detail, the consensus was the following:
·
Strengthen existing institutions rather than creating new ones.
·
Improve communication and information exchange particularly through the use of electronic
media and "personal computer" (PC) technology.
·
Reduce uncertainties in the regional impact of the global 1.5ºC/20 cm scenario by data
generation, case studies, and modelling, obtaining improved probability estimates on sea-level
rise and other climate change.
·
Continue the interdisciplinary interaction of the Task Team in order to provide quantitative
information to member states.
The latter point of quantifying results, based on the best physical or economic models, is considered the
penultimate goal of this joint UNEP/IOC programme.
Physical Processes
Climate change involves much more than RSL rise and temperature increase; precipitation,
evaporation, humidity, wind velocity, hurricanes, cloudiness, insolation, ocean currents, waves, mixing,
riverine input, etc., are all important variables (q.v., Figure 2). In order to strengthen quantitative
information transfer to governments, regional climate models nested in coupled ocean-atmosphere global
circulation models are needed, along with a vigorous, stable, long-term in situ verification programme,
coupled with an active multidisciplinary research effort which should include examination of the historical,
geological and archeological records in order to supplement direct measurements. Understanding future
shoreline migration is arguably the first priority in the region based on current information, but if
precipitation changes (for example) are markedly underestimated, the impact on agriculture and coastal
ecosystems could be far more important. To this end, participation in efforts such as the World Climate
Programme, with significant international visibility by scientists from the region, is absolutely necessary to
improve the physical basis upon which quantitative information is provided to ecologists, sociologists,
economists, politicians and managers.
Ecological Aspects
Identification of the most vulnerable ecosystems requires more of a microscale approach than the
mesoscale thinking required of the physical processes discussed above. Preparation of a regional map
with a classification scheme showing areas and ecosystems most vulnerable to climate change is a
massive, but necessary undertaking. Seagrass beds, coral reefs, mangroves (particularly the black
mangrove) and coastal lagoons are probably the most critical habitats to be mapped. Associated with the
critical habitats are species that utilize them as feeding and/or nursery grounds. Of vital concern to these
critical habitats are climate related impacts from the sewage and toxic wastes of nearby human
population centres and agricultural regions. Conversely, impacts of saline intrusion on local fresh water
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Response to Future Climatic Conditions...
supplies and inundation particularly during storms of seaside population centres, are critical concerns to
local residents; high population density islands such as Barbados, and cities with rapidly rising RSL such
as Galveston, Port au Prince, Puerto Cortes, New Orleans and Cartagena, are particularly vulnerable.
Socioeconomic Issues
Before effective socioeconomic responses to climatic changes can be initiated, there is a need to reduce
significantly the degree of uncertainty about the likelihood, extent and direction of such changes. The
most vulnerable "system" in the socioeconomic and health sectors is the credibility of those making
impact assessments. Governments and institutions will revert to procrastination as the most viable
response to weak forecasting, rather than to improving information development and dissemination, risk
spreading and diversification, or to reducing levels of fixed commitments. Some countries such as Costa
Rica, for example, have already established new building set-back laws for construction along the coasts;
others, Florida for example, have locally opted for massive beach replenishment programmes. Most small
island States, which numerically constitute a substantial fraction of governing units, do not have the
financial resources nor the technical expertise to develop appropriate socioeconomic responses to
climate change. Probably the greatest single socioeconomic scenario that individual governments must
prepare for is a significant international migration of populations from highly vulnerable locales to areas
where safety and the quality of life is deemed to be better. To prepare for such future change, a
catalogue of institutional responses needs to be developed along with specification of conditions under
which those responses should be implemented.
Synthesis
H.L. Mencken once said "For every complex problem there is a solution that is simple, neat, and
wrong." With this caveat in mind, an attempt to synthesize much of the implications of climatic changes in
the region is given in Table 2. Three subjective levels of vulnerability to rises in sea level and temperature
are chosen and assigned to the ecosystems and socioeconomic topics outlined in the Terms of
Reference (q.v., Table 1). While on a site-specific scale many of the estimated impact levels will be
different, on a regional scale vulnerability to most climatic changes per se is judged low to moderate.
However, due to other pressures on the marine environment, and to human efforts to deal with the effects
of these pressures, the vulnerability of society to climatic changes increases. In many cases the future
impacts on society of non-climatic factors may far exceed those due to climatic changes. It is important,
therefore, for policy considerations, to view this synthesis in a proper context, which is, climatic changes
will exacerbate environmental changes already ongoing and documented in other studies.
From the entries in Table 2, it is clear that the Task Team was most concerned with tourism, both
because of its economic importance and because it is crucial to the social fabric in most of the island
states. Appended to the concern over the impacts on tourism, is that of tropical storms and beaches since
they both are associated with that industry. Only the impact on deltas was considered high for purely
ecological reasons. Several entries were considered to have moderate risk due to both temperature and
sea level rise (estuaries, wetlands, salinas, and lagoons), and hence are more vulnerable because either
effect could cause stress. Table 2 does not reflect our overriding concern for mangroves and coral reefs,
which are not excessively vulnerable to the 1.5°C/20 cm scenario, but being of such importance to the
ecological health of the Intra-Americas Sea (and indeed to subtropical/tropical regions globally), are
worthy of special mention outside the confines of this study (D'Elia et al., 1991).
MODELLING
Numerical and Scenario Models of Climate Change
Wigley and Santer (1993) give a very detailed discussion of the possible future climate of the
Intra-Americas Sea (cf. IPCC, 1990a). They compare the results of four numerical models that predict
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CEP Technical Report No. 22
future surface air temperature change and precipitation change for each of the four seasons. Each model
calculates the effect on temperature and rainfall of doubling all the greenhouse gases, expressed as
doubled C02 (2XC02). All four numerical models are global models, but Wigley and Santer only report the
regional results of interest herein. Figure 9, from Wigley and Santer (pers. comm.) show the model results
for annual mean temperature and annual mean precipitation respectively. Results from atmospheric
General Circulation Models (GCMs) for future climate on a regional scale must be interpreted very
cautiously because of the limitations in numerically simulating such a complex problem as climate.
Cautiously then, the range of annual average modelled temperature change (Figure 9a) and annual
average modelled precipitation change (Figure 9b), are discussed below.
Table 2. Implications of Climatic Changes in the Intra-Americas Sea
(L) Low Impact; (M) Moderate Impact; (H) High Impact
Terms of Reference
(a) RSL 20 cm
(b) SST 1.5°C
Ecosystems: Level of Vulnerability*
Agriculture L
L
Beaches H
L
Coastal Lakes
L
L
Coastal Plains
M
L
Coral Reefs
L
M
Deltas H
L
Estuaries M
M
Fisheries L
M
Forests L
M
Lagoons M
M
Mangroves M
L
Rivers L
M
Seagrass Beds
M
M
Wetlands M
M
Socioeconomic: Level of Vulnerability*
Coastal Zones
L
M
Cultural Heritage
M
L
Human Migration
L
M
Public Health
L
M
Settlements and Structures
M
L
Tourism H
M
Tropical Storms
L
H
*These levels of vulnerability reflect only the WMO/ICSU/UNEP (1985) climate scenario detailed in the
Terms of Reference, and must be considered as issues that exacerbate other problems such as
population pressure, pollution, subsidence, coastal erosion, construction, warfare, etc.
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Response to Future Climatic Conditions...
The annual average temperature change caused by effective C02 doubling shows a fairly
consistent result in each GCM: an increase of 2°C to 4°C is calculated. Details of increased annual
averaged temperature change are different from GCM to GCM, but in general the continental boundaries
of the Intra-Americas Sea are modelled to have higher annual average temperatures than the islands.
Annual average precipitation changes due to effective C02 doubling also shows significant variability
between GCMs, but each model shows that the zero contour (in millimeters per day), which runs through
the centre of the Caribbean Sea, is the dominate feature of the calculation. Precipitation in the region is
strongly influenced by tropical storms, however, which are not in these GCMs.
Although the results shown in Figure 9 vary considerably between GCMs, the general conclusion is
in agreement with the WMO/ICSU/UNEP (1986) scenario of rising temperature. Climate however is the
sum of many geophysical factors (q.v., Figure 2), the greenhouse gases only being one of them, and
there may be competing factors (particularly on a regional scale) that can modify these modelled results.
Human activities such as massive deforestation can alter the balance of factors that add up to Earth's
climate, and the prudent observer will interpret the results shown in Figure 9 cautiously.
An alternative method of considering future climate is the scenario modelling (Lamb, 1987)
discussed earlier. Gallegos and his colleagues have applied the scenario model to the Intra-Americas
Sea. As with Wigley and Santer (1993), Gallegos et al. (1993) have focused on seasonal variability as
potentially having a greater short-term implication than the mean (annual) changes. Based on analysis of
actual data they foresee larger seasonal fluctuations than at present, a result not dissimilar from the
numerical model results.
Gallegos et al. carry the results of their scenario modelling further, and give indications of the
effect of increased intra-season variability on the region's marine waters. They foresee that a few
consecutive hot summers have the potential to:
· readjust coastal sea level, which may affect the fresh water balance in coastal ecosystems;
· modify the location and magnitude of shoreline migration;
· alter patterns of economically important marine species;
· cause sufficient changes in surface currents to effect marine transportation and contingency
plans for spills of hazardous substances; and
· reorder air-sea interaction which may shift local weather patterns such as precipitation.
When comparing results from GCMs and from scenario models, there are caveats that must be
considered. As eloquent as Lamb's (1987) arguments for scenario models are, there are questions as to
whether or not past climate is a harbinger of the future. Similarly, the GCMs are well known to have
limitations, and the parameterization of certain physics (notably clouds) and unmodelled effects of
volcanism (AGU, 1992) are of concern in our confidence of the 2xC02-1xC02 forecasts. Of particular
importance is "How is the global surface temperature change distributed?"
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CEP Technical Report No. 22
Figure 9a. Annual average temperature change due to effective CO2 doubling from GCMs
of the Geophysical Fluid Dynamics Laboratory (GFDL), Goddard Institute for Space Studies
(GISS), Oregon State University (OSU), and the National Center for Atmospheric Research
(NCAR). Maps courtesy of Wigley and Santer (1993).
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Response to Future Climatic Conditions...
Figure 9b. Annual average precipitation change due to effective C02 doubling from GCMs
MacCracken et al. (1990) have explored temperature patterns in the Northern Hemisphere using
paleoclimate reconstructions from the time periods of relative global warmth. MacCracken (pers. comm.)
has kindly provided two such reconstructions: the mid-Holocene (6000 ybp) minus the latter half of the
19th century (q.v., Figure 4) and the Eemian interglacial optimum (125,000 ybp) minus the latter half of
the 19th century; these are shown in Figure 10 for winter (lower panel) and summer (upper panel) along
with a similar meridional profile of predicted temperature change from the four GCMs (q.v., Figure 10).
For the tropical/subtropical region with which this report is concerned, there are some remarkable
differences.
All three profiles in Figure 10 show that the surface temperature will be larger at high latitudes, a
pattern consistent with all IPCC forecasts (Houghton et al., 1992). However, both the Holocene and the
Eemian reconstructions show that south of about 35°N (i.e., in the tropics and subtropics) the
temperature was cooler during periods of global warmth. The GCMs show quite the opposite: warming at
all latitudes with 2xCO2-1xCO2 predictions. Readers are reminded that the WMO/ICSU/UNEP (1986)
scenario with which we are dealing is for a 1.5°C increase in the regions surrounding the Intra-Americas
Sea that is part of a global 1.5°C increase. Figure 10 leaves us with important questions that are
unresolved.
Lest there remain ambivalence in the reader's mind concerning future climate, a global forecast of
temperature and sea level to the year 2 100 is given in Figure 11. The stippled area for each projection
represents the range of uncertainty in the "best guess" IPCC scenario for 1992 (Houghton et al., 1992) as
calculated by Wigley and Raper (1992) for the global equilibrium temperature change ( T2x=2.5°C due to
the equivalent C02 doubling. Based on the revised IPCC estimates, the global temperature and sea level
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CEP Technical Report No. 22
will be 2.5°C and 48 cm higher in 2100 than today, slightly lower values than in the IPCC (1990a)
estimates. With respect to the WMO/ICSU/UNEP (1986) scenario dealt with herein (1.5°C and 20 cm by
2025 respectively), Figure 11 suggests that the 1.5°C temperature rise is most likely to occur ca. 2060
and the 20 cm sea level rise ca. 2050. Although the range of uncertainty is much larger at 2100 than at
2050, there is little doubt in the Wigley and Raper (1992) calculation that by the middle of the next
century, a warmer Earth is expected, but forecasting the T2x scenario on a regional basis is fraught with
additional uncertainty.
Numerical Models of Climatic Change Socioeconomic Impact
A class of PC-based models to assist decision makers has been developed by Engelen et al.
(1993). The authors write that socioeconomic systems may be influenced by climatic change in ways
ranging from minor or very local to drastic and nationwide. Any such changes will be superimposed on
trends already present in these evolving systems. Therefore, it is vital to anticipate dangers, as well as
new opportunities, as soon as possible. To allow governments and policy-makers to play an active role in
managing these socioeconomic systems effectively, they should be provided with tools that will permit
them to explore impacts in their full holistic, spatial, and temporal contexts. Decision support systems are
designed to assist in such tasks. The most essential part of such systems is a set of tools, mostly
quantitative models and methods, which at relatively low cost, allow the user to analyze and evaluate a
range of possible futures resulting from different scenarios and hypotheses.
Figure 10. Paleoclimate and greenhouse model comparisons of the meridional profile of
seasonal average surface temperature in the Northern Hemisphere
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Response to Future Climatic Conditions...
As part of a larger decision environment, a two-level mathematical modelling framework, geared to
study the effects of climatic change on the level of the individual island or mainland state, is being
developed (Engelen et al., 1993). The long-range mechanisms of change are modelled in a classic, non-
equilibrium spatial interaction model. This model then feeds regional growth coefficients into a low-level
cellular model that deals with the short-range location and interaction mechanisms. This technique of
linked models is necessary in order to capture successfully the effects resulting from climatic change on
the appropriate scales. The prototype is a first, mostly conceptual step towards a system for use in real
world applications.
The Engelen et al. model can best be operated using a 386 personal computer with a mathematics
co-processor or a 486DX, a Super-VGA monitor, and a "windows" operating system. The model
components are illustrated in Figure 12. On the high level, long range interactions are modelled by means
of a dynamic spatial interaction sub-model. The regional growth coefficients are fed into a low-level
cellular sub-model to preform the allocation on a detailed scale based on short range interaction
mechanisms. Both sub-models will store and retrieve information from the same geographical database.
In use, decision-makers are able to view the effects of three sea level rise scenarios on a hypothetical
"Caribbean" island. In the no-sea- level- rise scenario, population growth and external demand for goods
and services are the cause of most land use changes, but in the 20-cm- sea- level- rise in 40 years
scenario (0.5 cm/yr), much of the change was due to loss of mangroves and beaches. The case of sea
level fall, a real possibility for some islands in the Intra-Americas Sea, was ecologically dominated by
coral reef stress and mangrove forest advance, and economically by population growth. Other aspects of
socioeconomic effects can be simulated in such models, and they are easily learned. Plans are being
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CEP Technical Report No. 22
formulated to apply the model to a real "Caribbean" island, and to make the technology available to
interested policy-makers and planners throughout the region.
CONCLUSION
The atmospheric concentration of CO2, the primary anthropogenic greenhouse gas, is undoubtedly
increasing, and as the upper right hand panel of Figure 7 shows, the increase is clearly associated with
human population growth (Idso, 1989). Atiyah and Press (1992) write "If current predications of
population growth prove accurate and patterns of human activity on the planet remain unchanged,
science and technology may not be able to prevent either irreversible degradation of the environment or
continued poverty for much of the world." Lending institutions, such as the World Bank (1992) recognize
the crucial role of population growth, and not only echo sentiment with Atiyah and Press, but have
created programmes to link population and sustained development. Thus, the box in Figure 7 marked
"human activity" not only shows a linkage to global "climatic changes", it also shows a relationship to
"other human-induced changes" particularly on the local or regional level. In the near-term, it is the local
anthropogenic effect of human activity that dominates "physical", "ecological", and "socioeconomic"
change in the Intra-Americas Sea.
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Response to Future Climatic Conditions...
Figure 11. Global temperature (upper curves) and sea level (lower curves) projections for
the various IPCC 1992 scenarios.
A range of projections within each stippled area are calculated for the "best-guess" set of ice-melt
and climate modes. Redrawn from Wigley and Raper (1992), the projections only show the
anthropogenic component of a future climate, with natural variability superimposed on them.
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CEP Technical Report No. 22
Figure 12. Schematic of the two-level PC-based socioeconomic numerical model.
On the high-level, long range interactions are modelled by means of a dynamical spatial
interaction model. The regional growth coefficients are fed into a low level cellular model to
perform the allocation on a detailed scale based on short range interaction mechanisms. Both
models will store and retrieve information from the same geographical data base. From Engelen
et al. (1993).
In order to understand these physical, ecological, and socioeconomic interactions on the marine
and coastal environment, six Task Teams on Implications of Climate Change have been organized by
UNEP: the Mediterranean, Southeast Pacific, South Pacific, East Asian Seas, South Asian Seas, and the
Wider Caribbean Region. Each area has unique problems, but each shares the common concern of
changing air and water circulation, coastal geomorphology, coastal ecosystems, soil degradation,
freshwater resources, precipitation patterns, terrestrial ecosystems, coastal industries and settlements,
and littoral zone population dynamics. The underlying thread oftentimes emphasizes negative aspects of
climate change; this isn't necessarily universal. Whenever established patterns are disturbed, vested
interests tend to exhibit a concern. Rising RSL is probably of more concern in the Intra-Americas Sea
than rising temperature, but it is too early to be definitive.
There is a realistic expectation that certain positive benefits may accrue from climate change; the
local response to global change is simply not predictable at this time. What may be perceived as negative
to one sector of society in the region may be beneficial to another. Two examples:
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Response to Future Climatic Conditions...
·
a change in precipitation associated with a temperature fluctuation may allow the introduction
of different crops but perhaps at the sacrifice of others;
·
an increase in the alongshore component of the wind could increase coastal upwelling and be
a benefit to fisheries, yet it may be a cause for concern to agronomists dealing with aerial
erosion.
A truly challenging and interesting problem will be to identify and explore the legal and institutional
implications under the diverse systems and governments which characterize a region that has been
influenced by so many native, European, and African cultures.
Of primary concern is the availability of adequate data. The Caribbean Sea sea-level network,
which was in such good repair for earlier regional programmes such as BOMEX (the Barbados
Oceanographic and Meteorological Experiment) in 1969, is now marginally adequate. From a climate
perspective, a sea level observing network must be reestablished and include marine meteorological
data, geodetic leveling data, sea water chemistry data, and ancillary site-specific information. Because of
the many short records of sea level and weather, and the difficulty of making conclusions based on them,
a concurrent programme of geological, archeological, and historical data analysis is considered a
cost-effective means of strengthening those conclusions. There must also be rapid and free exchange of
the observations, a basin-wide commitment to common problems, a responsibility to calibrate and
intercompare measurements, and adequate sustained funding.
Establishing and maintaining a modem sea-level/weather observing network is absolutely
necessary to document and ultimately forecast climate change impacts. It is particular important in such
an observing system to have the ability to record extremes in sea level, and in temperature of both the
water and air; it is in the extreme events that climate change impact may be most noticeable. Figure 13 is
an example of such a observing station that has both meteorological and oceanographic instruments, part
of what is known as the C-MAN network. C-MAN stations are typically configured to record and report via
GOES variables such as air and sea temperature, wind velocity, sea level, precipitation, insolation, cloud
cover, etc. The system is completely digital, and data can be acquired either directly via a PC and modem
or from the Global Telecommunications System (the WMO real-time data exchange network). Careful
placement, maintenance, and calibration of sensor packages such as illustrated in Figure 13 not only will
provide information to unequivocally detect climate change, but form the database for sustained
economic development.
Some writers urge "the time for action to prevent global warming is now; we should not spend more
money on studies". Such well-meaning persons quite misunderstand the level of uncertainty in the
climate record and in models. For example, Hanson and Maul (1993) report that the thermometer at Key
West was moved 17 times during the 136 years of record that they studied. Oftentimes the location of the
Key West instrument, its condition, and its calibration, etc., or even how daily means were calculated,
were unknown. Yet it is from the patching together of such records (and Key West is one of the best!) that
scientists attempt to determine climate change. Whatever time for "action" it is, that action must first be to
obtain records that are accurate, reliable, and not biased by urbanization or other locale-specific
influences, if only to give the next generation of scientists proper data for model verification. Today's
"politically correct" frenzy for action must include a sustained commitment to improved forecasts and
improved observations.
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CEP Technical Report No. 22
Figure 13. Photograph of a typical C-MAN station
showing the meteorological and oceanographic instrumentation needed for detecting local
climate change and for socioeconomic modelling of climate change impacts. The instruments are
typically located in an exposed site in order to avoid anthropogenic influences such as the
microenvironment change associated with infrastructure development at airports or seaports. The
mast is typically 5 m (15 feet) tall and the ground space required is typically 1 m2 (10 feet2).
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Response to Future Climatic Conditions...
ACKNOWLEDGEMENTS
The scope of the work summarized herein could not have been possible without the unprecedented
willingness of the members of the UNEP/IOC Task Team to share their work: Anders Alm, Colombia;
Ruben Aparicio, Venezuela; Erik Blommestein, Trinidad & Tobago; Alfonso Botello, Mexico; James
Broadus, USA; Gillian Cambers, UK; Donald de Sylva, USA; Guy Engelen, The Netherlands; James
Evans, USA; Frank Gable, USA; Artemio Gallegos, Mexico; Calvin Gray, Jamaica; Kirby Hanson, USA;
Malcolm Hendry, Barbados; Aurelio Mercado, Puerto Rico; John Milliman, USA; Frank Müller-Karger,
USA; Lloyd Shapiro, USA; Naresh Singh, St. Lucia; Samuel Snedaker, USA; Dana Thompson, USA;
Vance Vicente, Puerto Rico; and Roger White, Canada. In addition I wish to express my gratitude to the
University of Miami's Cooperative Institute for Marine and Atmospheric Studies (CIMAS) whose staff
contributed so much, and especially to Jill Reed; to Mike MacCracken, John Walton, and Stanley Grotch
at the Lawrence Livermore National Laboratory whose work was used to construct Figure 10; to the staff
of the UNEP/CEP Regional Coordinating Unit, especially Salvano Briceñio, Beverly Miller, Vicente
Santiago, and Orjan Mohlund; to the IOC and Subcommission IOCARIBE Secretariats, primarily Gunnar
Kullenberg and Fernando Robles, who financially supported part of this work; to David Senn and Andrew
Ramsay for their contributions to the graphics; and to Hugo Bezdek and Donald Hansen of the NOAA
Atlantic Oceanographic and Meteorological Laboratory in Miami, Florida, who permitted this work through
salary and staff support.
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Response to Future Climatic Conditions...
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Washington D.C., 27 pp.
Alm, A., E. Blommestein, and J. Broadus, 1988: Climatic changes and socioeconomic impacts in the
Caribbean. In: Implications of Climate Changes in the Wider Caribbean Region. UNEP (OCA)/CAR
WG.I/INF.3, pp. 107-127.
Alm, A., E. Blommestein, and J.M. Broadus, 1993: Climatic changes and socioeconomic impacts.
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Aparicio, R., 1993: Meteorological and oceanographic conditions along the southern coastal boundary of
the Caribbean Sea, 1951-1986. Chapter 6, Op. Cit., pp. 100-114.
Atiyah, M., and F. Press, 1992: Population Growth, Resource Consumption, and a Sustainable World. A
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Berger, W.H., and L.D. Labeyrie, 1987: Abrupt climatic change - an introduction. Chapter 1, in W.H.
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Chao, B.F., 1991: Man, water, and global sea-level. EOS, 72(45), 491.
de Sylva, D.P., 1993: Human health. Chapter 14, Op. Cit., pp. 325-332.
D'Elia, C.F., R.W. Buddemeier, and S.W. Smith, 1991: Workshop on Coral Bleaching, Coral Reef
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Maryland, College Park MD 20742, 49 pp.
Diaerfeldt G., and M.D. Hendry, 1987: An 8,000 year Holocene sea-level record from Jamaica:
implications for the interpretation of the Caribbean reef and coastal history. Coral Reefs, 5, 165-169.
Engelen, G., R. White, and I. U1jee, 1993: Exploratory modelling of socio-economic impacts of climatic
change. Chapter 16, Op. Cit., pp. 350-368.
Gable, F.J., 1993: Marine habitats: selected environmental and ecological charts. Chapter 10, Op. Cit.,
pp. 217-26 1.
Gallegos, A., S. Czitrom, J. Zavala, and A. Fernandez, 1993: Scenario modelling of climate change on
the ocean circulation of the Intra-Americas Sea. Chapter 3, Op. Cit., pp. 55-74.
Gray, C., 1993: Regional meteorology and hurricanes. Chapter 5, Op. Cit., pp. 87-99.
Hansen, J., and S. Lebedeff, 1988: Global surface air temperatures: update through 1987. Geophys. Res.
Lett., 15(4), 323-326.
Hanson, K., and G.A. Maul, 1993: Analysis of temperature, precipitation, and sea-level variability with
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Op. Cit., pp. 193-213.
Hardin, G., 1971: Nobody ever dies of overpopulation. Science, 171(3971), 527.
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Hendry, M., 1993: Sea-level movements and shoreline change. Chapter 7, Op. Cit., pp. 115-161.
Hodell, D.A., J.H. Curtis, G.A. Jones, A. Higuera-Gundy, M. Brenner, M.W. Binford, and K.T. Dorsey,
1991: Reconstruction of Caribbean climate change over the past 10,500 years. Nature, 352,
790-793.
Houghton, J., B. Callander, and S. Varney, 1992: Climate Change 1992, Supplementary Report to the
IPCC Scientific Assessment. Cambridge Univ. Press, Cambridge, 224 pp.
Idso, S.B., 1989: Carbon Dioxide and Global Change: Earth in Transition. IBR Press, Tempe AZ, 292 pp.
IPCC (Intergovemmental Panel on Climate Change), 1990a: Climate Change, the IPCC Scientific
Assessment. Cambridge Univ. Press, Cambridge, New York, Port Chester, Melbourne, Sydney,
339 pp.
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245 pp.
IPCC, 1990c: Climate Change, the IPCC Response Strategies. WMO/UNEP, Geneva, 270 pp.
Lamb, H.H., 1982: Climate, History, and the Modern World. ©Methuen & Co., Ltd., 387 pp.
Lamb, P.J., 1987: On the development of regional climatic scenarios for policy-oriented climatic-impact
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MacCracken, M.C., M.I. Budyko, A.D. Hecht, and Y.A. Izrael (eds.), 1990: Prospects for Future Climate.
Lewis Pubs., Inc., Chelsea, MI, 270 pp.
Maul, G.A., 1992: Temperature and sea level change. In Levi, B.G., D. Haferneister, and R.A. Schribner
(eds.), Global Warming: Physics and Facts. ©American Institute of Physics, New York, pp. 78-112.
Maul, G.A., and S.R. Baig, 1993: Glossary of scientific terms. Chapter 17, Op. Cit., pp. 369-381.
Mercado, A., J.D. Thompson, and J.C. Evans, 1993: Requirements for modelling of future storm surge
and ocean circulation. Chapter 4, Op. Cit., pp. 75-84.
Milliman, J.D., 1993: Coral reefs and their response to global climate change. Chapter 13, Op. Cit., pp.
306-321.
Müller-Karger, F., 1993: River discharge variability including satellite-observed plume dispersal pattern.
Chapter 8, Op. Cit., pp. 162-192.
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National Academy Press, Washington, D.C., 239 pp.
Oceanus, 1987/88: Vol. 30(4). Caribbean Marine Science. Woods Hole Oceanographic Institution,
Woods Hole, MA 02543.
Pugh, D.T., N.E. Spencer, and P.L. Woodworth, 1987: Data holdings of the permanent service for mean
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Shapiro, L.J., 1982: Hurricane climatic fluctuations. Part 11: Relation to large-scale circulation. Mon. Wea.
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Snedaker, S.C., 1993: Impact on mangroves. Chapter 12, Op. Cit., pp. 282-305.
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UNEP (United Nations Environment Programme), 1987: Action plan for the Caribbean Environment
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Van Sertima, I., 1976: They Came Before Columbus. Random House, New York, 288 pp.
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313 pp.
Vicente, V.P., N.C. Singh, and A.V. Botello, 1993: Ecological implications of potential climate change and
sea-level rise. Chapter 11, Op. Cit., pp. 262-28 1.
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Sequences of Caicos Platform with an Introductory Evaluation of South Florida. Amer. Geophys.
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Wigley, T.M.L., and S.C.B. Raper, 1992: Implications for climate change and sea-level of revised IPCC
emissions scenarios. Nature, 357, 293-300.
Wigley, T.M.L., and B.D. Santer, 1993: Future climate of the Gulf/Caribbean basin from the global
circulation models. Chapter 2, Op. Cit., pp. 31-54.
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APPENDIX: GLOSSARY AND ABBREVIATIONS
Aerosol: Atmospheric particles with radii ranging from 10-3 to 10 µm (micrometers), which are important
in scattering of radiation.
Air-Sea Interaction: The scientific study of the rates of energy transfer from the atmosphere to the
ocean, and from the sea to the air; considerable feedback exists between the two fluids.
Albedo: The ratio of total radiant energy reflected from a body to the total radiant energy incident upon it;
Earth's albedo, is typically 0.4, the ocean's albedo is less than 0. 1, but cloud albedos can be 0.9 or
greater.
Altithermal Period: A dry, warm postglacial period 7500-4000 ybp (cf. Little Climatic Optimum).
Anthropogenic: Involving the impact of humankind on nature; induced or altered by the presence and
activities of humans.
Anticyclonic: Fluid flow having a sense of rotation (clockwise in the northern hemisphere) opposite to
Earth's, rotation, and associated with an oceanic or atmospheric high pressure cell.
Aquifer: A subterranean layer of unconsolidated material containing water, which may be connected to
the sea.
Atoll: A torus-shaped organic reef enclosing a lagoon in which there is no pre-existing land, and being
surrounded by open sea.
Bathymetry: The science of measuring ocean depths to determine sea floor topography.
Beach: A zone of unconsolidated material that is in alongshore or onshore- offshore active transport.
Benthic: A zone of ocean bottom always under water; pertaining to organisms that live there.
Bruun Rule: An empirical rule of beach erosion for a closed system in which there is no external source
or sink of sand, given by W·Z/D where W is the active beach width, Z is sea level rise, and D is
tide range; W/D is often found to be ~100.
Canalization: The restricting of river flows into channels or canals; oftentimes this prevents flooding, in
deltas but leads to a loss of the very sediment that builds deltas.
Carbon Dioxide (C02): The primary radiatively active atmospheric gas responsible for the greenhouse
effect; its concentration is approximately 350 parts per million (ppm).
Carbonate (CO =
3 ): A salt or ester of carbonic acid; the most common form in the Intra-Americas Sea is
calcium carbonate (CaC03), i.e., limestone.
Caribbean Current: A branch of the North Equatorial Current (NEC) passing through the Lesser Antilles
and flowing into the Gulf of Mexico through the Yucatan Channel.
Catchment Area: Geographical region from which rainfall drains into a common river system; also called
drainage area.
Cellular Automata: A numerical modelling approach where a large number of small areas (cells) are
used to represent details in a physical or socioeconomic process, and where the cells are
mathematically connected in a computer algorithm.
CFC (chlorofluorcarbon): A non-radiatively active anthropogenic compound made of one or two carbon
atoms, chlorine, and fluorine; CFC's interact with UV radiation to chemically destroy ozone in the
stratosphere.
Chlorophyll: A green organic molecule active in photosynthesis; it can be detected in ocean waters by
satellite sensors such as the CZCS and (if successful) SeaWIFS.
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Circulation: The three-dimensional change associated with the motion of the ocean or the atmosphere,
and giving rise e.g., to surface currents and winds respectively.
Climate: The statistical collective of weather for a given region over a specified length of time, typically
30 years.
Climatology: The scientific study of climate.
Cloud Feedback: Radiation from Earth at visible and infrared wavelengths is absorbed and reemitted by
clouds and can interact again with Earth's surface; this interaction is termed feedback.
C-MAN: Coastal-Marine Automated Network.
Coastal Zone: The area of Earth's surface from near the coast to the continental shelf break (~200 m
isobath) where marine species (saltwater) dominate the ecology.
Compaction: The geological process whereby a soil mass loses pore space, becomes more dense, and
thus increases its bearing capacity.
Coral Bleaching: A condition of corals when photosymbiotic organisms, e.g., dinoflagellates such as
zooxanthellae, are forced to leave the host coral animals.
CORG: Organic Carbon; a generic term for marine organic matter.
Coriolis Force: An apparent force on moving particles when measured relative to a rotating coordinate
system; the force is to the right in the Northern Hemisphere and is proportional to 2 sin(y) where
is Earth's angular velocity and y is latitude.
Cryosphere: The region of Earth dominated by ice.
CZCS (Coastal Zone Color Scanner): An experimental global ocean color sensing (visible wavelength)
multispectral scanning radiometer launched in 1978 on the NASA NIMBUS-7 satellite (no longer
operating).
Delta: An alluvial deposit formed at the mouth of a river or a tidal inlet.
Downwarping: Subsidence of a broad region of Earth's crust.
Ecosystem: A community of animals, bacteria, and plants, and their inter-relation with their immediate
chemical and physical environment.
Eemian Period: North European climatostratographic and floral stage equivalent in time to the
Riss/Würm interglacial about 125,000 ybp.
Ekman Transport: The volume flow that occurs at right angles to the wind in the Northern Hemisphere; it
arises from the balance of the Coriolis force and wind stress. Alongshore coastal winds lead to
upwelling or downwelling.
El Niño: A condition, originally applied to the surface waters of the eastern equatorial Pacific Ocean,
wherein the usual cold, marine-life-supporting surficial. waters are replaced by unusual warm
waters; it was thought to occur around Christmas, hence the Spanish name for "The Child."
Energy: The capacity for doing work, expressed as a result of motion (kinetic), of availability to cause
motion (potential), of being associated with light (radiant), of the exchange of heat and cold
(thermal), etc.
ENSO: (El Niño-Southern Oscillation) A term that connects the oceanic phenomenon (El Niño) with the
atmospheric phenomenon (Southern Oscillation) leading to the realization of the global
consequences of air-sea interaction (see TOGA).
Equilibrium Temperature: The temperature Earth would achieve in due time after an increase in
greenhouse gases.
Estuary: A tidal bay formed from the drowning of a non-glaciated river valley juxtaposed to the ocean.
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Eustatic: Simultaneous world-wide change in sea level associated with growth or melting of continental
and/or mountain glaciers (cf. Glacial).
Fishery: The business of catching and selling fish (e.g., being associated with single boats: artisanal), or
type of fish (e.g., bottom feeders: demersal); also the study of fishing in a particular environment
(e.g., estuarine) or with an age class (e.g., juvenile).
Florida Current: That branch of the Gulf Stream System flowing through the Straits of Florida from Dry
Tortugas to Cape Canaveral.
Forecasting: In ceophysical fluid dynamics, the art of predicting future states of the atmosphere or ocean
through computer models (numerical forecasting), through projection of observed trends
(persistence forecasting), or through comparisons with prior epochs (scenario forecasting).
GCM: General Circulation Model.
Geoid: An equipotential (level) surface (i.e., one to which, at every point, the plumb line is perpendicular).
Specifically, the figure of the earth considered as the level surface of a motionless 35,0,p ocean,
where 35,0,p is the specific volume of a 35 psu, O°C , ocean, at a particular time.
Geomorphology: The study of the form of the earth and the general configuration of its surface.
Geosphere: The solid earth or land as compared to the atmosphere or hydrosphere.
GFDL: NOAA Geophysical Fluid Dynamics Laboratory, located in Princeton, New Jersey U.S.A.
GISS: NASA Goddard Institute for Space Studies located in New York, New York U.S.A.
Glacial: Pertaining to ice that is on land, thus affecting eustatic sea level; sea ice does not contribute to
changes in sea level.
Greenhouse Effect: The analogy to the atmosphere of how a greenhouse works, i.e., that the Earth is
some 30°C warmer because certain gases (notably water vapor and C02) allow shortwave
radiation (sunlight) to pass through to the surface, but absorb some of the longwave (infrared)
radiation emitted by the ground and sea.
Groundwater: Water below the water table (minimum water-well depth) as distinguished from interflow
and soil moisture.
Gulf Stream System: The primary oceanic current system of the western North Atlantic Ocean including
the Caribbean Current, the Yucatan Current, the Loop Current, the Florida Current, and the "Gulf
Stream" proper.
Halocarbon: A molecule of carbon and any of the five chemical elements fluorine, chlorine, bromine,
iodine, and astatine.
Holocene: The most recent geological epoch, usually taken as the last 10,000 years or so.
Hot Snap: A short (several day or week-long) period of elevated temperature; the opposite of a cold
snap.
Hydrology: The science of Earth's waters, especially concerning evaporation, precipitation, and the
character of water in streams, lakes, and under ground.
Hypersalinity: Extremely high salinity condition, often leading to detrimental conditions for marine
organisms.
ICSU: International Council of Scientific Unions.
Infrastructure: The basic facilities upon which a modem human community is dependent such as roads,
schools, ports, dams, etc.
Interglacial: The periods in Earth's history when glaciers are a minimum in size and extent, and the
temperatures are warm, such as at present.
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Intra-Americas Sea: The region of the tropical and subtropical western North Atlantic Ocean that
includes the Guianas coast of South America, the Caribbean Sea, the Gulf of Mexico, the
Bahamas, and Bermuda; approximately bounded by 0°-30°N latitude and 50°W-100°W longitude.
IOC: Intergovemmental Oceanographic Commission of UNESCO.
IOCARIIBE: IOC Subcommission for the Caribbean and Adjacent Regions (cf. Intra-Americas Sea; Wider
Caribbean Region).
IPCC: Intergovernmental Panel on Climate Change of the WMO, ICSU and UNEP.
Lagoon: A shallow pond generally separated from the open sea (cf. atoll, coral reef).
Leveling: The art of determining the vertical height difference between two points on Earth. Geodetic
leveling is extremely precise and is always referenced to the vertical control datum.
Little Climatic Optimum: The period in Earth's history, approximately 8,000 to 5,000 ybp, when mean air
temperatures were 1-2°C warmer than today (cf. Altithermal Period).
Little Ice Age: The period in Earth's history, approximately the years 1300 to 1800 AD, when mean
surface air temperatures were 1-2°C colder than today.
Littoral: The newshore zone, typically encompassing the high tide line to below the low tide line (in some
usage, out to the continental shelf break, i.e., -200 m).
Loop Current: That portion of the Gulf Stream System flowing into the Gulf of Mexico beyond the
Yucatan Channel, turning (or looping) an ticyclonic ally within the Gulf, and exiting through the
Straits of Florida.
Mangrove: One of several genera of tropical and subtropical trees and shrubs that have prop roots and
that grow in the shallow waters of the coastal zone.
Mean Sea Level: The mean surface water level determined by averaging heights at all stages of the tide
over (traditionally) a 19-year period. Mean sea level is not an equipotential surface (i.e., not the
geoid).
Medieval Warn Epoch: That period in Earth's history, approximately the years 800-1200 AD, when air
temperatures were 1-2°C warmer than the Little Ice Age, and similar to today's.
Mesoscale: A length dimension associated with a circulation feature, typically of the order of 100-1,000
km; the scale upon which ocean eddies and hurricanes occur.
Methane (CH4): A colorless naturally occurring and anthropogenically generated atmospheric
greenhouse gas that contributes to the radiative warming of Earth (cf. carbon dioxide).
Milankovitch Cycle: Regularly changing insolation due to variations in Earth's orbit around the sun,
theorized to cause ice ages; for the next 5,000 years Earth will undergo decreasing insolation due
to orbital parameters.
Mixed Layer: Vertical zone in the ocean between the surface and the thermocline where wave action
mix%-.-s the water to a uniform temperature and salinity (typically 25-100 m thick).
Model: A mathematical or heuristic description of a physical, chemical, biological, geological or
socioeconomic process, which can be prognostic (forecasting) or diagnostic (analytical).
Morphology: The scientific study of form and structure, especially in biology and geology.
Nitrous Oxide (N20): A colorless naturally occurring and anthropogenically generated atmospheric
greenhouse gas that contributes to the radiative warming of Earth (cf. carbon dioxide).
NASA: U.S. National Aeronautics and Space Administration.
NCAR: National Center for Atmospheric Research located in Boulder, Colorado U.S.A.
NEC (North Equatorial Current): A westward flowing ocean current driven by the northeast
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Trade Winds; in the Atlantic Ocean it enters the Caribbean Sea primarily through the Windward,
Mona, and Anegada Passages.
NECC (North Equatorial Counter Current): An ocean current flowing eastward near the equator; in the
Atlantic Ocean it seems to be related to the retroflection zone off the Guianas.
Nitrate (N0 -
3 ): A salt or esther of nitric acid; the most abundant and readily assimilable form of nitrogen
for marine organisms; like phosphate, it is an essential nutrient.
NOAA: U.S. National Oceanic and Atmospheric Administration.
OSU: Oregon State University located in Corvallis, Oregon U.S.A.
Ozone (03) Layer: The stratum of the atmosphere between 10 and 50 km above the surface where 03 is
highly concentrated; also called the ozonosphere. 03 is a faintly blue gaseous form of oxygen
formed photochemically when ultraviolet light interacts with oxygen. Ozone reacts with CFC's which
reduces the ozonosphere's UV absorbing properties.
Paleoclimate: The climate of a time in the geological past.
PC: Personal Computer (usually refers to IBM design systems using Intel microprocessors).
Phaeopigment: Chlorophyll-like plant molecules that can contribute to water discoloration. They can be
sensed by satellite systems such as the CZCS.
Phosphate (P): An ionic form of phosphorous occurring in nature; an essential marine nutrient.
Population Density: The number of humans per unit area.
Productivity: In oceanography, it is the amount of carbon fixed by living organisms per unit area per unit
time.
PSMSL: IOS Permanent Service for Mean Sea Level located in Bidston, Merseyside, U.K.
PSU (Practical Salinity Units): The modem units of salinity; very approximately the same as per mille
(0/00) or parts per thousand or grams of salt per kilogram of seawater.
Radiation: The energy output of an object, usually expressed with the wavelength band such as infrared
(3-20 µm), microwave (1-50 cm), net (all wavelengths), ultraviolet (2000-4000 Å), visible (400-700
nm), etc.
Retroflection: An ocean current zone off the Guianas where the northwestward moving crossequatorial
flow turns anticyclonically and continues out into the open Atlantic Ocean (see the book cover for a
CZCS image of the retroflecting flow).
Rossby Wave (or -wave): Horizontal wave motion in a rotating fluid, such as the ocean or atmosphere,
when the change in Coriolis parameter (f) with latitude (y) is considered a constant ( = f / y).
RSL (Relative Sea Level): The long-term change in ocean water level measured by a tide gauge,
including the (usually unknown) vertical motion of the gauge plus the change in the water due to
eustatic, steric, and/or wind-driven effects.
Salina: A shallow salt marsh or pond separated from the ocean but flooded by high tide.
Salinity: The grams of salt in a kilogram of seawater (cf. psu); specifically, the total amount of dissolved
solids by weight when all the carbonate has been converted to oxide, the bromide and iodide to
chloride and all organic matter is completely oxidized.
Saltwater Intrusion: The inflow of saltwater into a normally freshwater aquifer; associated with sea level
rise and/or groundwater extraction.
Seagrass: Members of either the Hydrocharitaceae or Zosteraceae families - of bottom growing
grass-like spermatophytes, usually found in waters less than 10 m deep, and important in
stabilizing unconsolidated bottoms.
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Sea Level (or water level): The height of the surface of the sea at any time. In surveying and mapping the
term "sea level" should be avoided, but if used it should be with the meaning of mean sea level.
Sea level is not an equipotential (level) surface (cf. Geoid).
SeaWIFS, (Sea Wide-Field Sensor): Follow-on ocean color multispectral scanner planned to be orbited
by NASA in 1993.
SLOSH (Sea Lake Overland Surges from Hurricanes): Storm-surge model for predicting the height of
water levels associated with a tropical storm or hurricane.
Specific Volume Anomaly ( ): The excess of the actual specific volume (reciprocal of density,
s, t, p
) of seawater at any point in the ocean (
)
s, t, p
over the specific volume of seawater of salinity
s=35 psu and in situ temperature t=0°C at the same pressure ( 35, 0, p ); = s, t, p - 35, 0, p .
Spheroid: A mathematical figure closely approaching the geoid in form and size, and used as a
reference for geodetic surveys.
SST (Sea Surface Temperature): The temperature of the upper meter of the water column, usually
measured with a thermometer from a bucket sample.
Steric: In oceanocraphy, steric refers to the expansion or contraction of the water column due to the
distribution of temperature and salinity.
Stratosphere: The region of the atmosphere above the troposphere or from about 10 to 25 km,
characterized by ozone in addition to the normal gases.
Sulfate: A salt or ester of sulfuric acid (H2SO4), that occurs naturally and anthropogenically in the ocean
and the atmosphere (where it is associated with acid rain).
Sverdrups (Sv): A commonly used measure of oceanic volume transport equal to 106m3s-1 or 1
gigaliter/second; Florida Current volume transport is 30 Sv, but the Amazon River is only 0.2 Sv.
Tectonic: The investigation of the origin and evolution of the broad structural features of Earth,
particularly associated with the motion of crustal plates (plate tectonics).
Thermocline: Vertical zone in the ocean below the mixed layer where the temperature decreases rapidly
with increasing depth (typically 500- 1,000 m thick).
Tidal Benchmark: A bronze disk firmly cemented into a solid foundation that serves, as the vertical
(leveling) reference for a tide gauge or tide staff.
Tide Gauge: A device for measuring water level as a function of time, and which is referenced to tidal
benchmarks through periodic leveling surveys.
TOGA (Tropical Ocean - Global Atmosphere): A term describing the relationship between the Pacific
Ocean's interaction with (and forcing of) the whole atmosphere; also the name of a scientific
research programme.
Topography: The configuration of a surface including its relief. In oceanography the term is applied to a
surface such as the sea bottom (cf. Bathymetry) or a surface of given characteristics within the
water mass.
Transport: In fluid flows, it is a measure of amount per unit time; used to define volume transport (liters
per second), heat transport (watts), mass transport (grams per second), etc.
Troposphere: The atmospheric shell closest to Earth's surface, extending approximately 10 km upwards;
the zone where weather occurs.
Turbidity: A measure of the amount of suspended matter in water or aerosols in air; a-more precise term
is attenuation which is the sum of scattering and absorption.
UNEP: United Nations Environment Programme.
UNESCO: United Nations Educational, Scientific, and Cultural Organization.
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Upwelling: The vertical motion of seawater (as distinct from rising air) often associated with Ekman
Transport in the ocean.
UV: (ultraviolet): Radiation invisible to the naked eye, with wavelength shorter than violet (i.e., less than
400 nm).
Wetlands: Areas that are covered with fresh surface water for some period of each year on a recurring
seasonal basis.
Wider Caribbean Region: UNEP term for the Gulf of Mexico/Caribbean Sea/Bahamas/Guianas region;
cf. IOCARIBE.
Wind Stress: The force per unit mass per unit area exerted by atmospheric flow on the ocean's surface;
units are dynes per square centimeter.
WMO: World Meteorological Organization of the United Nations.
ybp: Years Before the Present.
Yucatan Current: That portion of the Gulf Stream System that flows northward along the Belize-Mexico
coast through the Yucatan Channel into the Gulf of Mexico where it becomes known as the Loop
Current.
Zooxanthellae: An algal cell living symbiotically in the cells of certain invertebrate animals such as
corals.
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