text: Global warming is a term used to describe the trend of increases in the average temperature of the Earth's atmosphere and oceans that has been observed in recent decades. The scientific opinion on climate change, as expressed in the United Nations Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report in 2001 and explicitly endorsed by the national science academies of the G8 nations April 2005, is that the average global temperature has risen 0.6 ± 0.2 °C since the late 19th century, and that it is likely that "most of the warming observed over the last 50 years is attributable to human activities" [1]. The increased volumes of carbon dioxide and other greenhouse gases released by the burning of fossil fuels, land clearing and agriculture, and other human activities, are the primary sources of the human-induced component of warming. The natural greenhouse effect keeps the Earth about 33 °C warmer than it otherwise would be; adding carbon dioxide to a planet's atmosphere, with no other changes, will make that planet's surface warmer.