Global mean land-oceantemperature change from 1880-2010, relative to the 1951-1980 mean. The black line is the annual mean and the red line is the 5-year running mean. The green bars show uncertainty estimates. Source: NASAGISS
Comparison of surface based (blue) and satellite based (red: UAH; green: RSS) records of global mean temperature change from 1979-2009. Linear trends plotted since 1982.
The map shows the10-year average (2000-2009) global mean temperature anomaly relative to the 1951-1980 mean. The largest temperature increases are in the Arctic and the Antarctic Peninsula. Source: NASA Earth Observatory
Global warming is the increase in the average temperature of Earth's near-surface air and oceans since the mid-20th century and its projected continuation. According to the 2007 FourthAssessment Report by the Intergovernmental Panel on Climate Change (IPCC), global surface temperature increased by 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 20th century.[A] Most of the observedtemperature increase since the middle of the 20th century has been caused by increasing concentrations of greenhouse gases, which result from human activities such as the burning of fossil fuel anddeforestation. Global dimming, a reduction of sunlight reaching the surface as a result of increasing atmospheric concentrations of human-made particulates, has partially countered the effects of warminginduced by greenhouse gases.
Climate model projections summarized in the 2007 IPCC report indicate that the global surface temperature is likely to rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F)during the 21st century. The uncertainty in this estimate arises from the use of models with differing sensitivity to greenhouse gas concentrations and the use of differing estimates of future...