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The impact of four degree temperature rise

A 4 °C rise in global average temperatures is possible this century under some emissions scenarios

Our four degree map outlines some of the potential impacts of a 4 °C (7 °F) temperature rise.

In 2007 we produced the four degree map on behalf of HM Government. Climate scientists from other institutions also contributed their most up to date research on climate impacts at the time.

The map details potential impacts of a 4 °C (7 °F) rise in global average temperature above the pre-industrial climate average. This projection was generated using the Met Office Hadley Centre's HadCM3 computer model and shows that the 4 °C rise would not be spread uniformly across the globe.

To create the map the computer model was run many times, for two different greenhouse gas emission scenarios. These are two of the socio-economic scenarios developed by the Intergovernmental Panel on Climate Change (IPCC), representing greenhouse gas emissions (and other emissions such as aerosols) for future development without active mitigation against climate change.

These projections demonstrated that the land would heat up more quickly than the sea whilst high latitudes, particularly the Arctic, would have greater temperature increases. In this case, the average land temperature increase would be 5.5 °C.

You can view the plotted changes as an Four degree interactive map or download it as an Climate change on Google Earth.

Advances in science

This map was created using scientific evidence that was available in 2007. In 2007 the Intergovernmental Panel on Climate Change (IPCC) published its 4th Assessment Report (AR4) which provided a clear view of scientific knowledge about climate change at that time. The IPCC's reports provide research-based information about the causes and consequences of climate change, and assess measures for lessening the severity of climate change and the potential for adapting to its consequences.

In September this year the IPCC began its 5th Assessment Report (AR5), this is the first comprehensive update on the science since AR4 was published.

Find out more about the IPCC and how the Met Office is involved.

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