Itwasoncethoughtthatairpollutionaffectedonlytheareaimmediatelyaroundlargecitieswithfactoriesand/orheavyautomobiletraffic.Today,weknowthatalthoughthesearetheareaswiththeworstairpollution,theproblemisliterallyworldwide.Onseveraloccasionsoverthepastdecade,aheavycloudofairpollutionhascoveredtheentireeasternhalfoftheUnitedStatesandledtohealthwarningseveninruralareasawayfromanymajorconcentrationofmanufacturingandautomobiletraffic.
Infact,theclimateoftheentireearthmaybeaffectedbyairpollution.Somescientistsfeelthattheincreasingconcentrationofcarbondioxideintheairresultingfromtheburningoffossilfuels(coalandoil)iscreatinga“greenhouseeffect”—holdinginheatreflectedfromtheearthandraisingtheworld’saveragetemperature.
Ifthisviewiscorrectandtheworld’stemperatureisraisedonlyafewdegrees,muchofthepolaricecapwillmeltandcitiessuchasNewYork,Boston,Miami,andNewOrleanswillbeunderwater.Anotherview,lesswidelyheld,isthatincreasingparticulatematterintheatmosphereisblockingsunlightandloweringtheearth’stemperature—aresultthatwouldbeequallydisastrous.Adropofjustafewdegreescouldcreatesomethingclosetonewiceageandwouldmakeagriculturedifficultorimpossibleinmanyofourtopfarmingareas.
Atpresentwedonotknowforsurethateitheroftheseconditionswillhappen(thoughonerecentgovernmentreportpreparedbyexpertsinthefieldconcludedthatthegreenhouseeffectisverylikely).Perhaps,ifweareverylucky,thetwotendencieswilloffseteachotherandtheworld’stemperaturewillstayaboutthesameasitisnow.