Environmental Problems, Their Causes, and Sustainability 1

the troposphere. Electricity generated by coal is responsiblefor about 42% of this input, transportation24%, industrial processes 20%, and residential andcommercial uses 14%. Exhale, start a car, turn up thethermostat, turn on a light, burn leaves or a fireplacelog, or do just about anything, and you add carbondioxide to the troposphere. Burning a gallon of gasoline(which weighs about 2.7 kilograms, or 6 pounds)produces about 9 kilograms (20 pounds) of CO 2 .A second process is deforestation and clearing andburning of grasslands to raise crops and build cities,which release CO 2 and N 2 O. Third is the raising of anincreasing number of cattle and other livestock that releasemethane as a result of their digestive processes.A fourth process is cultivation of rice in paddies anduse of inorganic fertilizers that release N 2 O into thetroposphere.What Role Does the United StatesPlay in Greenhouse Gas Emissions?Number OneThe United States emits more greenhouse gasesas a nation and on a per person basis than anyother country.The United States is by far the world’s largest emitterof CO 2 . Although the United Staates has only 4.6% ofthe world’s population it produces an estimated 24%of the annual global emissions. The U.S. is followed bythe European Union (12%), China (11%), Russia (7%),Japan (5%), and India (5%). However, the combinedCO 2 emissions of the Asian countries of China, India,Japan, and South Korea are over twice the emissions ofEuropean Union countries and are approaching thoseof the United States.According to the IPCC, emissions of CO 2 from U.S.coal-burning power and industrial plants are verylikely to exceed the combined CO 2 emissions of 146 nationswhere three-fourths of the world’s people live.CO 2 emissions from U.S. motor vehicles are roughlyequivalent to those produced by everything that powersthe Japanese economy.The U.S. also emits large quantities of CH 4 . Mostcomes from landfills (35% of all U.S. CH 4 emissions),domesticated livestock and their manure (26%), naturalgas and oil systems (20%), and coal mining (10%).In addition, the United States has the world’shighest per capita CO 2 emissions, followed byAustralia, Canada, and the Netherlands. During a 70-year lifetime, each U.S. citizen typically emits about454 metric tons (500 tons) of CO 2 into the troposphere.Is the Troposphere Warming?Very LikelyThere is considerable evidence that the earth’stroposphere is warming.Here are five of many IPCC findings that support thescientific consensus that it is very likely (90–99% probability)that the troposphere is getting warmer. First, the20th century was the hottest century in the past 1,000years (Figure 21-2, bottom left). Second, since 1861 theaverage global temperature of the troposphere nearthe earth’s surface has risen 0.6°C (1.1°F) over the entireglobe and about 0.8°C (1.4°F) over the continents.Most of this increase has taken place since 1980.Third, the 16 warmest years on record have occurredsince 1980 and the 10 warmest years since 1990.The hottest year was 1998, followed in order by 2002,2001, and 2003. Based on climate records going back to1500, the summer of 2003 was the hottest Europe experiencedin 500 years. More than 19,000 deaths were attributedto the heat. Fourth, glaciers and floating seaice in some parts of the world are melting and shrinking(Case Study, below). Fifth, during the last centurythe world’s average sea level rose by 0.1–0.2 meter (4–8inches), partly from runoff from melting ice and partlybecause of the volume of ocean water expands whenits temperature increases.Afew scientists have been skeptical of atmosphericwarming. They pointed to a 1990 study showing thatsince 1979 temperature measurements near the earth’ssurface have been rising while satellite and other measurementsshowed no appreciable warming of the midand upper troposphere. However, in 2002 and 2004 researchersanalyzed these data and found much thesame warming in these areas as thermometers show atte earth’s surface.The terms global warming and global climatechange are often used interchangeably but they are notthe same. Global warming refers to temperature increasesin the troposphere, which in turn can cause climatechange. Global climate change is a broader termthat refers to changes in any aspects of the earth’s climate,including temperature, precipitation, and stormintensity. It can involve global warming or cooling, butour focus will be on global warming. Global warmingshould not be confused with the problem of ozone depletion(Table 21-2), as discussed in Section 21-9.Case Study: Warning Signals fromthe Earth’s Ice and Snow: MeltdownsAre Under WaySome of the world’s floating ice and land-basedglaciers are slowly melting, reflecting less incomingsunlight back into space, and helping warm thetroposphere further.The average temperature of the troposphere isstrongly affected by the vast amounts of frozen waterfound as ice and snow near the earth’s poles and inmost of the world’s mountain glaciers. In the Arctic region,this water is locked up in ice caps that coverGreenland and floating sea ice in the Arctic Ocean. The466 CHAPTER 21 Climate Change and Ozone Loss