Projected global average temperatures

Average global atmospheric warming over the last century is almost 0.8°C. According to the National Aeronautics and Space Administration (NASA), the global average surface temperature has risen by approximately 0.6°C in just 30 years (NASA, 2008). Twelve of the warmest years on record have all occurred in the last 13 years. Every year from 2001 to 2007 was warmer than every year from 1991 to 2000, with the exception of 1998 (Hadley Centre, 2008).

During the 21st century, the IPCC projected that global average temperature could increase within the range of 1.1°C to 6.4°C above 1990 levels, which is about 1.6°C to 6.9°C above global average temperatures prior to 1750 (IPCC, 2007b).

Temperature increases are projected to vary significantly at different latitudes, with much greater average increases in temperature in the higher latitudes. Higher altitudes and areas further inland will also experience greater temperature increases, and the frequency and severity of extreme temperatures is also likely to be very significant.

Observed temperature increase is in the upper part of the range projected by the IPCC and emissions growth is currently greater than the most emissionsintensive scenario of the IPCC. Unless the trends of the past 30 years are an aberration, and if a global solution remains illusive, the worst case climate change scenario is unfolding.

Based on climate model studies and advanced studies of climatic and Earth system history, Hansen et al (2008) conclude that additional global warming of about 1°C is likely to be dangerous. Makiko Sato of Columbia's Earth Institute concludes that 'the temperature limit implies that carbon dioxide exceeding 450 parts per million is almost surely dangerous'. As James Hansen states (Hansen et al, 2008):

If global emissions of carbon dioxide continue to rise at the rate of the past decade, this research shows that there will be disastrous effects, including increasingly rapid sea-level rise, increased frequency of droughts and floods, and increased stress on wildlife and plants due to rapidly shifting climate zones.

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