Climate Change and Ozone Loss

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1 Climate Change and Ozone Loss During the past 900,000 years, the earth has undergone a series of cold glacial periods followed by warmer interglacial periods. The past 10,000 years has been an interglacial period. Scientists gather clues about climate change by examining long cores from deep within the earth, making direct measurements, tracking temperatures, and taking air samples. The International Panel on Climate Change is a network of over 2000 of the leading climate experts from 70 nations.

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3 21-2 The Earth's Natural Greenhouse Effect The greenhouse effect is a natural process that warms the earth's lower troposphere and surface. It occurs because greenhouse gases warm the atmosphere by absorbing some infrared radiation from the earth's surface. The two major greenhouse gases are water vapor and carbon dioxide.

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5 21-3 Climate Change and Human Activities Since the industrial revolution began, human activities such as the use of fossil fuels, deforestation, raising cattle, cultivation of rice, and the use of nitrogen fertilizers have increased the release of greenhouse gases. The U.S. is the world's largest emitter of carbon dioxide and also emits large quantities of methane.

6 The scientific consensus is that the earth is getting warmer. Although the two terms are often used interchangeably, global warming refers to temperature changes in the troposphere and global climate change refers to any changes in the earth's climate, including temperature, precipitation, and storm intensity. Some of the dangers of climate change include melting sea ice, which will change the albedo, further warming the atmosphere, and the loss of mountain glaciers, which are an important water source for many countries. The biggest long-term climate danger may be the potential for melting of land-based ice sheets on Greenland.

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9 21-4 Projecting Future Changes in the Earth's Temperature Complex mathematical models called coupled global circulation models help scientists project future temperature changes.

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11 Scientists warn that the main problem is the rapid pace of change. Climate change will affect the availability of water resources, alter wind patterns and weather, change ocean currents, flood coastal areas, and alter economics around the world.

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14 21-5 Factors Affecting the Earth's Temperature The oceans help moderate the earth's temperature. Changes to carbon dioxide levels are accelerating the global water cycle, which will reduce the availability of fresh water and cause regional cooling. Global warming may also increase cloud cover. Jet condensation trails may be contributing to global warming. Atmospheric pollutants may somewhat counteract the effects of greenhouse gases, but as pollution levels drop, the effect is reduced. Climate change is a complex phenomenon and many factors are involved, including atmospheric pollution levels, carbon dioxide, methane emissions, and soils.

15 21-6 Possible Effects of a Warmer World A warmer world could change the distribution of plants and animals. Ocean currents could shift and sea levels could rise, threatening delicate aquatic ecosystems and flooding coastal areas. The economies of rich and temperate countries are likely to benefit from moderate global warming, while economies in poorer island, tropical, and subtropical countries will suffer.

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18 21-7 Dealing with the Threat of Global Warming Economists and policymakers disagree on how to deal with global warming. There are four schools of thought on what to do, ranging from doing nothing to act now. The most effective strategy is to reduce energy waste and encourage a shift from nonrenewable fossil fuels to renewable energy sources such as solar, wind, and hydrogen. Planting trees could help take up carbon temporarily. Carbon dioxide emissions could be stored in the deep sea or deep underground, but the effectiveness, costs, and possible unexpected effects of doing this are unknown. We can prepare for global warming by wasting less water, growing crops that need less water, not storing hazardous wastes on low-lying coastal areas, using dikes to protect low-lying cities from flooding, and expanding wildlife reserves toward the earth's poles.

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21 21-8 What Is Being Done to Reduce Greenhouse Gas Emissions? More than 170 nations have approved the Kyoto Protocol, designed to achieve reductions in carbon dioxide emissions by The United States has not signed the treaty, saying it would damage the economy and does not require emission reductions by countries such as China. Despite the U.S. position, most countries are going ahead with the treaty. They are establishing one of the world's largest commodity markets, in which treaty participants can buy and sell greenhouse gasemission allowances in the global marketplace. Various countries, businesses, and communities are reducing greenhouse emissions or setting targets to do so. We should work to delay or stop global warming while simultaneously preparing to adapt to it.

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24 21-9 Ozone Depletion in the Stratosphere The ozone layer keeps 95% of the sun's harmful UV radiation from reaching the earth's surface. Use of chlorofluorocarbons (CFCs) and other ozone-depleting compounds has lowered the average level of ozone in the stratosphere. One effect is seasonal ozone thinning over the poles. UV radiation can cause skin cancers and damage plants and animals.

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28 21-10 Protecting the Ozone Layer The consensus is that we should immediately stop producing all ozonedepleting chemicals. The Montreal Protocol and Copenhagen Protocol promise to cut emissions of CFCs. However, ozone will continue to be depleted for years because CFCs take time to reach the stratosphere and are persistent.

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