Global warming is the increase in the average temperature of the Earth's near-surface air and oceans since the mid-twentieth century and its projected continuation. Global surface temperature increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the last century.[1][A] The Intergovernmental Panel on Climate Change (IPCC) concludes that anthropogenic greenhouse gases are responsible for most of the observed temperature increase since the middle of the twentieth century,[1] and that natural phenomena such as solar variation and volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect afterward.[2][3] These basic conclusions have been endorsed by more than 40 scientific societies and academies of science,[B] including all of the national academies of science of the major industrialized countries
sourcehttp://en.wikipedia.org/wiki/Global_warming
