Four degrees too far

By Gareth Renowden 23/10/2009

The British government has stepped up its pre-Copenhagen campaign for a global emissions deal, yesterday releasing this interactive map of what a 4ºC temperature increase would mean for the world. Click on the map to explore the impacts listed across the bottom. A larger (full page) version is available here, and background here and here. At the launch in the Science Museum in London, Ed Miliband, the Energy and Climate Change Secretary emphasised the urgency:

’Britain’s scientists have helped to illustrate the catastrophic effects that will result if the world fails to limit the global temperature rise to 2 degrees. With less than 50 days left before agreement must be reached, the UK’s going all out to persuade the world of the need to raise its ambitions so we get a deal that protects us from a 4 degree world.’

The 4ºC projection can be thought of as a plausible worst case scenario – the sort of outcome that we have to take seriously when deciding on emissions reductions. Based on modelling done at the UK Met Office’s Hadley Centre (discussed at this recent conference, BBC coverage here), the map shows what could happen if global emissions continue to rise unchecked — but not when we would get there. Some model runs suggest it could be as early as the 2060s. One key point to note: a 4ºC rise in the global average does not mean a 4ºC rise everywhere. Some places (like NZ) will be shielded from the full warming by cool oceans, but in the Arctic, for instance, the rise could be as much as 15ºC, and over continental interiors such as the USA and Asia 6 – 8ºC. Large parts of central Australia will be 6ºC hotter — as will much of Antarctica. The planet will be radically transformed, and not in a good way. More coverage at the Telegraph, Independent and Guardian.