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i <br /> WHAT CAUSES' CLIMATE CHANGE . <br /> t <br /> j <br /> he debate is over. Scientists confirm the climate is changing <br /> g `' "If 1 could get adults and politicians <br /> i due to the increasing amount of greenhouse as in the at- FS Y . <br /> Ix <br /> mosphere . Americans on the whole believe that climate "' to do one thing, I 'd have them break <br /> change is real . A vast majority thinks the U . S . should reduce <br /> our dependence on of / and coal. " <br /> its GHG emissions . They also want a clear explanation of what causes <br /> climate change . —Kirk Tolfa, Occidental,CLIMATE CHANGE Is caused by a manmade blanket <br /> P ds the earth 11 years old <br /> For nearly all of life on Earth, a balance between energy entering and <br /> of carbon dloxide* It.hat surroun <br /> leaving Earth's atmosphere has existed . However, since the industrial <br /> and trap <br /> revolution , the balance has been disrupted , mostly by increased <br /> amounts of carbon dioxide from fossil fuel combustion . In the last <br /> century alone, carbon dioxide levels have increased by 25 % . At cur- <br /> rent rates of fossil fuel use, scientists predict that the carbon in the at <br /> will double by 2050 . They also say that we need to reduce <br /> J. <br /> our emissions by at least 60 percent in less than one hundred years . <br /> \� atmospher, a Global CO2 emissions <br /> (million tonnes) <br /> Year <br /> . . . 20 878 <br /> v� � 1990 . . . . . . . . . . . . . . . . . . . . . . . . . . . . <br /> . . 22 561 <br /> 1997 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <br /> 2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29575 <br /> 2020 . . . 36102 <br /> The greenhouse effect keeps Earth ' s average surface temperature a <br /> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . <br /> hospitable 60° . Without it, the average temperature would be about <br /> 0 . 4 ° . The greenhouse effect is caused by gases in the atmosphere, <br /> World Energy Outlook 2000, International Energy Agency <br /> such as water vapor, methane, and carbon dioxide, that trap much The U . S . is responsible for approximately 25 percent of current <br /> of the sun 's incoming energy. worldwide GHG emissions . <br /> E <br /> Global atmospheric concentration of CO2 <br /> Scientists predict many changes as a result of <br /> I . : . : <br /> parts per mllhen (PAm) E <br /> the rise in greenhouse gas . For example , by ° <br /> 3 <br /> the year 2100 California temperatures are <br /> } 70 <br /> Y <br /> forecast to increase between 2 - 9° F. Sea lev- <br /> els will rise . In fact, many changes are already 560 . 777 o <br /> happening . Alaska's winter temperatures have . <br /> 21 <br /> risen 8 degrees since the 1960s . Sea levels are <br /> 340 <br /> o <br /> already rising along coastlines worldwide, in- <br /> cluding California 's . Some economists fore- ago <br /> see that the costs of mitigating the cata - <br /> impacts of global climate change will 360 <br /> strophic h <br /> quickly outstrip our financial resources . AI - S <br /> FS sE ';',u.�i � a 3y '���R '£�t �`Y 4' viA is' a 6 a <br /> Pi <br /> hou h we must adapt to changes already <br /> t 9 p 280 -. f <br /> " underway, we also must focus on reversing l <br /> manmade causes of global climate <br /> the ma 9 260 <br /> change . The sooner we begin, the better. 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 t9t� 1990 2000 <br /> 16 <br />