Friday, February 02, 2007 / In depth - Climate change will spark extreme weather / In depth - Climate change will spark extreme weather
Excerpts :
The world has warmed by about 0.74°C in the last 100 years, and will warm a further 0.2°C per decade for the next two decades.
The IPCC said its “best estimate” was that temperatures would increase by 3°C by the end of the century, if carbon dioxide levels continue to rise as predicted.
Other studies have found that such a temperature rise would result in serious water shortages for billions of people, lower crop yields, the spread of tropical diseases and the mass migration of people, mainly in developing countries, away from the worst affected areas.
Temperatures could rise even higher, by 4°C, if “feedback” effects take place. One such effect would be if thawing Siberian permafrost releases large quantities of methane, a greenhouse gas more potent than carbon dioxide.
Another possibility feared by many scientists is that rising temperatures and drought could cause the Amazon rainforest to die. If that were to happen, the vast forest would turn from absorbing carbon from the atmosphere as it does at present to producing carbon dioxide.
The report noted that “the last time the polar regions were significantly warmer than present for an extended period (about 125,000 years ago), reductions in polar ice volume led to four to six metres of sea level rise.”
However, Peter Stott of the UK’s Met Office said although Arctic ice was disappearing, the melting of the massive Greenland ice sheet could take “thousands of years”. Accordingly, the IPCC estimates a sea level rise of between 18 centimetres and 59 centimetres by 2100, compared with the average between 1980 and 1999. But these estimates do not take account of possible feedback effects.


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