Global warming

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Global warming is the observed increase in the average temperature of the Earth's atmosphere and oceans in recent decades.

A few facts:
 * Earth's average near-surface atmospheric temperature rose 0.6 ± 0.2 °Celsius (1.1 ± 0.4 °Fahrenheit) in the 20th century.
 * increased amounts of carbon dioxide (CO2) and other greenhouse gases (GHGs) are the primary causes of the human-induced component of warming.
 * The first speculation that a greenhouse effect might occur was by the Swedish chemist Svante Arrhenius in 1897.
 * current literature estimates climate sensitivity in the range 1.5–4.5 °C (2.7–8.1 °F)
 * Models referenced by the Intergovernmental Panel on Climate Change (IPCC) project that global temperatures may increase between 1.4 and 5.8 °C (2.5 to 10.5 °F) between 1990 and 2100.
 * CO2 has an estimated atmospheric lifetime of 50 to 200 years.