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Global Climate Change - Effects Of A Warming Climate

species coral ranges figure

In 1990 the Intergovernmental Panel on Climate Change (IPCC) noted several early signs of climate FIGURE 3.5
Carbon dioxide sources, 2001
change in Earth's colder habitats. The average warm-season temperature in Alaska had increased three degrees in fifty years. Glaciers had receded and thinned by thirty feet in forty years. There was significantly less sea ice in the Bering Sea than in the 1950s. Permafrost had thawed, causing landslides, erosion, and local floods. Ice cellars in northern villages thawed, becoming useless. More precipitation fell as rain than snow, and snow melted faster, causing more running and standing water.

Since then, further evidence of global warming has been frequent and diverse:

  • Heat waves and unusually warm weather have been reported at numerous locales, resulting in increased levels of human heat-related illness and death.
  • Sea level rise, resulting from the expansion of warmer sea water and the melting of glaciers, is estimated at four to ten inches over the course of the twentieth century. Sea level rise has resulted in land inundation, coastal flooding, and erosion.
  • Incidents of heavy snowstorms and rainfall have increased.
  • Droughts have increased in frequency.
  • Mountain glaciers have continued to shrink, and have disappeared in lower latitudes. FIGURE 3.6
    Total world emissions of carbon dioxide, 1995 and 2035
  • Diseases formerly confined to tropical regions, including several mosquito-borne diseases, have increased their range to higher altitudes and latitudes.
  • Spring arrives earlier in many places.
  • Numerous biological species have shifted their ranges to occupy higher latitudes and higher elevations.

World carbon dioxide emissions from energy consumption, 1992–2001

In March 2002, in what is perhaps the most dramatic event resulting from global warming to date, the giant Larsen B ice shelf collapsed off the coast of Antarctica. (See Figure 3.14.) Ice shelves are thick blocks of ice that are continuations of the ice sheets that cover the Antarctic continent. The Larsen B shelf was larger than the state of Rhode Island and likely had existed since the end of the last ice age 12,000 years ago.

Global temperatures are predicted to continue to rise. Some of the major effects of global climate change, and the likelihood of their occurrence, were listed by the IPCC in 2001. Many of these predictions have drastic consequences for humans as well as for wildlife.

Global Warming and Human Health

Higher temperatures alone are killing some people, particularly young and old people in urban areas. Over 250 died during a heat wave across the eastern United States in the summer of 1999. Most of these heat-related deaths occur directly from heat-induced strokes and heart attacks.

Air quality also deteriorates as temperatures rise. Hot, stagnant air contributes to the formation of atmospheric ozone, the main component of smog. Poor air quality also aggravates asthma and other respiratory diseases.

Higher temperatures and increased rainfall could create ideal conditions for the spread of a host of infectious diseases by insects, including mosquito-borne malaria, dengue fever, and encephalitis. Some tropical diseases have already spread beyond their old ranges, affecting people at higher altitudes and latitudes. For example, dengue fever, once restricted to altitudes below 3,300 feet, was reported at altitudes above 4,000 feet in Central America in 1999, at 5,600 feet in Mexico in 1998, and at 7,200 feet in the Andes Mountains of Columbia in 1998. Similarly, malaria was detected at high altitudes in Indonesia in 1997. Expansion of malarial ranges have also been reported in parts of Africa. West Nile virus-induced encephalitis, which is native to Egypt and Uganda, was first seen in the United States in 1999; by 2003 it had spread throughout the continental U.S., except for Oregon.

U.S. energy consumption, 2001

Sources of methane, 2001

Sea Levels and Precipitation Patterns

The National Climatic Data Center reports that sea levels rose by as much as 10 inches in the twentieth century. The Climate Institute in Washington, D.C., forecasts a further rise of 8 inches by 2030 and 26 inches by 2100 if current trends continue. These would be caused by the FIGURE 3.9
U.S. energy consumption by energy source, 2001
expansion of seawater as it is warmed, as well as by melting glaciers and ice caps.

Rising sea levels would narrow or destroy beaches, flood wetland areas, and either submerge or require the costly fortification of shoreline property. Numerous coastal cities worldwide would be flooded. Rising waters would also intrude on inland rivers, destroying freshwater habitats, threatening human water supplies, and increasing the salt content of groundwater.

A warmer climate is also likely to shift the rain belt of the middle latitudes toward the poles, affecting rainfall patterns around the world. Wetter, more violent weather is projected for some regions. The opposite problem—too little water—could worsen in arid areas such as the Middle East and parts of Africa. Frequent droughts could plague North America and Asia as well. Some experts have suggested that "global warming" is too mild a term for an era marked by heat waves that will make certain regions virtually uninhabitable.

Decreasing Biological Diversity

Global biodiversity is also predicted to suffer from planetary warming. Certain ecosystems will shrink or be lost entirely, including cold-temperature habitats such as tundra, and specialized habitats such as coral reefs and coastal mangrove swamps. Other species expected to be heavily affected include those that require habitat within FIGURE 3.11
The effect of forests on carbon dioxide concentratios
Potential effects of volcanic eruptions on climate and the surrounding environment
Clouds and their effect on global temperature
Satellite photo of the Larsen B ice shelf retreating to the rock cliffs. (AP/Wide World Photos)
narrow bands of temperature and humidity, such as the monarch butterfly or the edelweiss flower.

Many ecosystems are expected to shift geographically toward more appropriate climate regimes. However, some species may be unable to migrate rapidly enough to cope with climate change at the projected rates. Species expected to be most successful, in fact, include opportunistic varieties such as weeds and pests. The EPA warned in 1988, "If current trends continue, it is likely that climate may change too quickly for many natural systems to adapt."


The ranges of most species depend, among other things, on temperature and climate. A number of plant and animal species have already shifted their geographic ranges in response to warming patterns. Range shifts have been reported in alpine plants, butterflies, birds, invertebrates, and mosquitoes.

A 1999 study by Dr. Camille Parmesan and colleagues showed that among surveyed European butterfly species, 63 percent had shifted their ranges northward. Moreover, these species had shifted their ranges by a distance corresponding to temperature rises on the European continent. Dr. Parmesan also showed that one California species, Edith's checkerspot butterfly, has been disappearing from the southern parts of its range, as well as from lower-elevation habitats. Similarly, a 1999 study of bird species in the United Kingdom revealed that ranges have shifted north by an average of 12 miles. In the Olympic Mountains in the state of Washington, biologists reported in 1994 that sub-alpine forests have shifted to higher elevations previously characterized by alpine meadows. In Monterey Bay, California, a 1995 study showed that invertebrate species such as snails and starfish have shifted north as well. In Germany, a study of mollusk species showed that 20 percent of species had shifted their ranges. Range shifts of mosquitoes are supported by the occurrence of mosquito-borne diseases such as dengue fever at more northern latitudes and at higher altitudes.


Some species will be unable to shift their ranges in response to global warming. There may be physical barriers that are difficult or impossible to cross—mountains, perhaps, or oceans or other bodies of water. The species they depend on for food or other resources may not have shifted their ranges. Or, species may encounter new competitors or predators as they try to move into new habitats. These species are likely to decline with global warming.

Population declines have recently been reported in a number of habitats and species. Mangrove forests have been inundated by water due to rising sea levels and are dying. Arctic species are particularly vulnerable. An Arctic bird species, the black guillemot, is declining because of reductions in the amount of floating sea ice—ice formed by frozen saltwater. This has resulted in decreased food availability for guillemots as well as a reduction in the number of available nesting sites. Adelie penguin populations have declined dramatically in Antarctica, probably because of a reduction in sea ice, which not only provides penguin habitat but is essential to the penguins' primary food source, krill. In the Monteverde cloud forest of Costa Rica, where a unique, moist habitat is created by large amounts of water mist, an altitudinal rise in the cloud bank has resulted in the extinction of some twenty frog species as of 1999. Declines in lizard populations have also been documented, as well as altitudinal shifts by populations of birds and bats.

An issue of particular concern is the loss of plant species due to global warming. Plants are often less able to shift their ranges than are animals, which are mobile. As plants form the basis of most ecosystems, the loss of plant species will impact animals as well. Several factors may limit the ability of trees to shift their ranges. First, seed dispersal by wind or by birds may not be fast enough to keep pace with climate change. In addition, trees are long-lived species with long maturation times, and it takes a considerable amount of time for forests to become fully established in new areas. In terms of altitudinal shifts, soils at high altitudes tend to be poorer than at lower altitudes. Consequently, some species may not be able to colonize at higher elevations.

In the United States, the Forest Service believes that Eastern hemlock, yellow birch, beech, and sugar maple forests will gradually have to shift their ranges northward by 300 to 600 miles if projected warming trends become a reality. Several of these ecosystems are likely to be severely limited by warming, however, and are likely to die out, along with the wildlife they shelter. Studies by World Wildlife Fund International report that more than half the world's parks and reserves could be threatened by climate change. Some U.S. parks believed to be particularly vulnerable include the Florida Everglades, Yellowstone National Park, the Great Smoky Mountains, and Redwood National Park in California.

Global warming will also threaten ecosystems in unexpected ways. In 2002 extensive forest damage was reported on the Kenai Peninsula near Anchorage, Alaska. Over 38 million dead spruce trees, some of them over a hundred years old, were cleared from 4 million acres of forest habitat. The cause of this catastrophe was an explosion in the number of spruce bark beetles. Spruce bark beetles have always preyed on spruce trees in the Kenai Peninsula, but have been reproducing much more quickly because of warm temperatures. This represents the worst insect decimation of forests ever reported in North America.


Coral reefs are among the ecosystems most immediately threatened by global warming. (See Figure 3.15.) Coral reef habitats are found in coastal marine waters in tropical areas, and are among the richest and most diverse of marine ecosystems. In fact, one-quarter of all marine species are found in coral reefs. The corals that form the basis of this ecosystem normally have a close relationship with different species of algae. This relationship benefits both members—the algae receive shelter and protection within the calcium carbonate skeletons of corals, and the corals receive nutrients from the algae. Coral bleaching occurs when the corals eject the algae with which they normally live. This process is called bleaching because the corals lose their normally bright colors and take on a stark, white appearance. Coral bleaching has been shown to result from unusually warm oceanic water temperatures. Coral may recover after a bleaching episode when temperatures cool down again and the algae return. However, if the ejected algae die during a bleaching episode, the corals are doomed as well.

Widespread coral bleaching was reported beginning in the 1990s. In the spring of 2002 coral bleaching affected numerous coral reef ecosystems, including the Great Barrier Reef off the coast of Australia, the largest coral reef in the world. This is the second major bleaching event in four years, and it is believed to be extending throughout tropical FIGURE 3.15
Coral reefs are among the most diverse ecosystems in the world. They are also immediately threatened by global warming, which has caused unprecedented episodes of coral bleaching in recent years. (AP/Wide World Photos)
Pacific coral reef systems. Professor Ove Hoegh-Guldberg, a leading authority on corals and coral bleaching, predicts that if warming trends continue, all coral will be extinct—and the diverse coral reef ecosystems lost—by 2030.


Turtles and other reptiles, such as lizards and crocodilians, are characterized by an unusual sex determination system called temperature-dependent sex determination. This differs from the chromosomal system familiar in humans and other mammals, where two X chromosomes (XX) result in production of females and an X and a Y chromosome (XY) lead to males. In species with temperature-dependent sex determination, sex depends on the temperature at which egg development occurs.

Global climate change has resulted in skewed sex ratios in several turtle species. Generally, warmer temperatures favor the production of females in these species. Among loggerhead turtles in Florida, for example, females made up 87 to 99.9 percent of the hatchling population in 1992, depending on the precise nesting site used. This was traced to warmer sand temperatures on beaches. Among Mississippi painted turtles, almost 100 percent of hatchlings were female in 1994. Continued production of large numbers of females and few or no males could have drastic implications for many turtle populations.

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