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[[Image:Rogerrevelle.jpg|thumb|right|200px|[[Roger Revelle]]]]

[[Image:Rogerrevelle.jpg|thumb|right|200px|[[Roger Revelle]]]]

'''Global warming''' is the idea that the Earth has warmed somewhat over the past few decades, and that the warming appears to be related to increases in carbon dioxide and other greenhouse gases. The possibility of adverse consequences has become a major concern for some environmentalists.

'''Global warming''' is the idea that the Earth has warmed somewhat over the past few decades, and that the warming appears to be related to increases in [[carbon dioxide]] and other [[greenhouse gas]]es. The possibility of adverse consequences has become a major concern for some environmentalists.

According to some research, warming comes and goes in natural cycles of approximately 1,500 years. During these natural periodic increases in the average temperature of the Earth's atmosphere, crops grow better in northern latitudes and deaths from extreme weather decrease. The large arctic island of [[Greenland]] was colonized during the [[Medieval Warm Period]], but the colonies there had to be abandoned during the [[Little Ice Age]] which followed.  

According to some research, warming comes and goes in natural cycles of approximately 1,500 years. During these natural periodic increases in the average temperature of the Earth's atmosphere, crops grow better in northern latitudes and deaths from extreme weather decrease. The large arctic island of [[Greenland]] was colonized during the [[Medieval Warm Period]], but the colonies there had to be abandoned during the [[Little Ice Age]] which followed.