Earth's mean surface temperature has increased by about 0.8 °C with about two-thirds of the increase occurring since 1980.

Earth's mean surface temperature has increased by about 0.8 °C with about two-thirds of the increase occurring since 1980.Climate model projections are summarized in the 2007 Fourth Assessment Report (AR4) by the Intergovernmental Panel on Climate Change (IPCC). They indicate that during the 21st century the global surface temperature is likely to rise a further 1.1 to 2.9 °C for their lowest emissions scenario and 2.4 to 6.4 °C for their highest.