Chapters 18 - Global Climate Change
I. Central Case: Rising Temperatures and Seas May Take the Maldives Under
A. A nation of low-lying islands, or atolls, in the Indian Ocean, the Maldives is known for its spectacular tropical setting, colorful coral reefs, and sun-drenched beaches.
B. Nearly 80% of the Maldives= land area of 300 km2 lies less than 1 m above sea level, and the highest point of ground is only 2.4 m.
C. The world= s oceans rose 10-20 cm this past century, and are expected to continue to rise as temperatures warm, causing melting ice caps to discharge water into the ocean.
D. The island= s government has evacuated residents from several of the lowest-lying islands in recent years.
E. The tsunami in December of 2004 destroyed large sectors of the islands, including both homes and infrastructure such as hospitals and modes of transportation.
F. Other effects included soil erosion, saltwater contamination of aquifers, and other environmental damage.
G. The tsunami was caused by an earthquake, but the rising sea level allowed it to inflict great damage on the low-lying islands.
H. Maldives islanders are not alone in the worries: the people of other island nations and mainland coastal areas of the world fear the future.
II. Earth= s Hospitable Climate
1. Changes in the long-term pattern of atmosphere conditions worldwide, involving temperature, precipitation, and storm frequency and intensity, are global climate change.
A. The sun and the atmosphere keep Earth warm.
1. The sun, the atmosphere, and the oceans exert more influence on Earth= s climate than all other factors combined.
B. A Greenhouse gases@ warm the lower atmosphere.
1. As Earth= s surface absorbs solar radiation, its temperature increases and it emits radiation in the infrared portion of the spectrum.
2. Some atmospheric gases absorb infrared radiation effectively and are known as greenhouse gases.
3. When these gases absorb heat, they warm the atmosphere (specifically, the troposphere) as well as Earth= s surface. This warming is known as the greenhouse effect.
4. The greenhouse effect is a natural phenomenon that has been increased through human activities.
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C. Carbon dioxide is the primary greenhouse gas.
1. Although carbon dioxide is not the most potent greenhouse gas on a per-molecule basis, its abundance in the atmosphere means that it contributes more to the greenhouse effect than other gases.
2. Carbon dioxide concentrations have increased and are currently at the highest level in at least 400,000 years.
3. In the last two centuries humans have been burning increasing amounts of fossil fuels in their homes, factories, and automobiles. At the same time we have cleared and burned forests, reducing the biosphere= s ability to absorb carbon dioxide from the atmosphere.
D. Other greenhouse gases add to warming.
1. Other greenhouse gases are increasing in the atmosphere.
a. We release methane into the atmosphere by tapping into fossil fuel deposits, raising large herds of cattle, disposing of organic matter in landfills, and growing certain types of crops, including rice.
b. Nitrous oxide is a by-product of feedlots, chemical manufacturing plants, auto emissions, and modern agricultural practices.
c. Ozone concentrations in the troposphere have increased b 36% since 1750.
d. Water vapor is the most abundant greenhouse gas, and its concentration increases as tropospheric temperatures rise.
E. Aerosols and other elements may exert a cooling effect on the lower atmosphere.
1. Microscopic droplets and particles can have either a warming or a cooling effect. Most tropospheric aerosols, such as the sulfate aerosols produced by fossil fuel combustion, may slow global warming in the short term.
F. The atmosphere is not the only factor that influences climate.
1. Milankovitch cycles are changes in Earth= s rotation and orbit around the sun, and they result in slight changes in the relative amount of solar radiation reaching Earth= s surface at different latitudes.
2. Oceanic circulation also shapes climate.
a. El Niño conditions occur when equatorial winds weaken and allow warm water from the western Pacific to move eastward, eventually prevent cold water from welling up in the eastern Pacific.
b. In La Niña events, cold surface waters extend far westward in the equatorial Pacific.
c. Many scientists today are exploring whether globally warming air and sea temperatures may be increasing the frequency and strength of El Niño events.
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d. North Atlantic Deep Water (NADW) is part of a circulation pattern that moves warm surface water northward toward Europe where cooler water then sinks and returns in the other direction.
III. Methods of Studying Climate Change
A. Proxy indicators tell us about the past.
1. Ice caps and glaciers have preserved tiny bubbles of ancient atmosphere.
2. Sediment beds beneath bodies of water can be analyzed to learn about the ancient vegetation in an area and, by extension, what the climate was like at the time.
3. These sources of indirect evidence, which substitute for direct measurements, are called proxy indicators.
4. Other proxy indicators include coral reefs and tree rings.
B. Direct atmospheric sampling tells us about the present.
1. Charles keeling of the Scripps Institution of Oceanography documented trends in atmospheric carbon dioxide concentrations starting in 1958.
2. Keeling= s data show that atmospheric carbon dioxide concentrations have increased from around 315 ppm to 378 ppm since 1958.
C. Coupled general circulation models help us understand climate change.
1. Coupled general circulation models (CGCMs) are computer programs that combine what is known about weather patterns, atmospheric circulation, atmosphere-ocean interactions, and feedback mechanisms to simulate climate processes.
2. Over a dozen research labs around the world operate CGCMs.
3. Tests suggest that today= s computerized models provide a good approximation of the relative effects of natural and anthropogenic influences on global climate.
IV. Climate Change Estimates and Predictions
1. The most thoroughly reviewed and widely accepted collection of scientific information concerning global climate change is a series of reports issued by the Intergovernmental Panel on Climate Change (IPCC).
A. The IPCC report summarizes evidence of recent changes in global climate.
1. Besides the data on increases in atmospheric concentrations of greenhouse gases, the 2001 IPCC report presented a number of findings on how climate change has already influenced the weather, Earth= s physical characteristics and processes, the habits of organisms, and our economies.
B. Sea-level rise and other changes interact in complex ways.
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1. Warming temperatures are causing glaciers to shrink and disappear in many areas around the world, and polar ice shelves are melting. This, combined with the warming temperature resulting in expansion of the water, is causing a rise in sea level.
2. Higher sea levels lead to beach erosion, coastal flooding, intrusion of saltwater into aquifers, and other impacts.
3. The record number of hurricanes and tropical storms in 2005, including Hurricane Katrina, left many people wondering if global warming was to blame.
C. The IPCC and other groups project future impacts of climate change.
1. In 2000, the U.S. Global Change Research Program issued a report highlighting the past and future effects of global climate change on the United States. The report developed a series of predictions.
2. Climate change will affect agriculture and forestry.
a. Some croplands could lose their ability to produce food, while other areas might see increased agricultural productivity.
b. U.S. forests may become more productive, but the frequency and intensity of forest fires could increase.
3. Freshwater and marine systems.
a. Erosion and flooding could alter the structure and function of aquatic systems.
b. Less precipitation in some areas would shrink surface water sources, affecting the habitats, organisms, and human health.
4. Human health.
a. There could be increased exposure to numerous health problems including respiratory ailments from air pollution and expansion of tropical diseases, as well as problems from storms and flooding.
b. Alternatively, there may be fewer diseases and injuries related to cold weather.
V. Debate over Climate Change
1. Within the scientific community the debate involves the details and mechanisms of climate change and the extent and nature of its likely effects.
2. In the wider culture, many people, primarily nonscientists, contest the findings and interpretations. Some of these skeptics have vested interests in continuing the use of fossil fuels, and some of them have much power to make policy.
3. A third area of debate involves how human societies should respond to climate change.
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A. Scientists agree that climate change is occurring but disagree on many details.
1. In the summer of 2005 the national academies of science from 11 nations issued a joint statement urging action.
B. Some challenge the scientific consensus.
1. The media have tried to portray both sides of the issue.
2. Many charge that the media have given the impression that the debate is even, when in fact there are far fewer skeptics than believers, and the relatively few greenhouse skeptics among scientists are often funded by fossil fuel-related industries such as those related to petroleum and automobiles.
C. How should we respond to climate change?
1. There is much debate about the economic and political costs of reducing greenhouse gas emissions, and whether the reduction should be voluntary, government regulated, or as a result of economic sanctions.
VI. Strategies for Reducing Emissions
A. Electricity generation is the largest source of U.S. greenhouse gases.
1. Conservation and efficiency can arise from new technologies, or from individual ethical choices.
2. Renewable sources of electricity can also reduce fossil fuel use.
B. Transportation is the second largest source of U.S. greenhouse gases.
1. One-third of the average American city is devoted to use by cars - including roads, parking, garages, and gas stations.
2. The typical automobile is highly inefficient. Close to 85% of the fuel you use does something other than move your car down the road.
3. Automobile technology is making possible alternatives such as electric vehicles, alternative fuels, hybrid vehicles, and hydrogen fuel cells.
4. Driving less and using public transportation are lifestyle choices that reduce reliance on cars.
C. Some international treaties address climate change.
1. In 1992, the United Nations convened the United Nations Conference on Environment and Development Earth Summit in Rio de Janeiro. Five documents were signed, including the U.N. Framework Convention of Climate Change (FCCC), which outlined a plan for reducing greenhouse gas emissions through a voluntary, nation-by-nation approach.
a. In the U.S., greenhouse emissions increased by over 13% in the 10 years following the Rio conference.
b. Germany and the United Kingdom both cut their greenhouse emissions by 13% to 18% during the same period.
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c. The decision was made to create a binding international treaty that would require all signatory nations to reduce greenhouse gas emissions. This is the Kyoto Protocol.
D. The United States has resisted the Kyoto Protocol.
1. The Kyoto Protocol was to take effect when nations responsible for 55% of global greenhouse emissions ratified it. That occurred in 2005 when Russia became the 127th nation to sign.
2. The United States, the world= s largest emitter of greenhouse gases, refuses to ratify the protocol, claiming it is unfair to industrialized nations.
3. Proponents of the Kyoto Protocol point out that the industrialized world created the problem and therefore should make the sacrifices necessary to solve it.
E. Some feel climate change demands the precautionary principle.
A. Many factors, including human activities, can shape atmospheric composition and global climate.
B. Scientists and policymakers are beginning to understand anthropogenic climate change and its environmental impacts more fully.
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