20thcentury 21stcentury africa china civilization climaticchanges consumption(economics) droughts earth(planet) east ecology economicconditions effectofclimateon effectofglobalwarmingon effectofhumanbeingson emigrationandimmigration environmentalarchaeology environmentalethics environmentalism epidemics fiction fossilfuels general globalization governmentpolicy history humanbeings humanecology humangeography internationalrelations internationaltrade moralandethicalaspects naturalresources nature overpopulation petroleumasfuel petroleumindustryandtrade physiologicaleffect psychologicalaspects religion religiousaspects renewableenergysources research rome socialaspects socialscience sustainability unitedstates weather weatherinart weatherinliterature