EGU 2012: four in five heat records due to climate change
This year’s EGU General Assembly in Vienna is not currently experiencing heat extremes. But worldwide the number of local monthly record-breaking temperature extremes is now five times on average what would be expected if the climate was stable. This means that four out of five recent records would not have taken place without climate change, said Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research Germany, in a meeting presentation so early in the morning that he dubbed the attending delegates “heroic”.
Rahmstorf calculated the monthly heat record ratio - the number of records divided by the number expected in a stationary climate - for the last 131 years of temperature observations. The global mean ratio was roughly five, but parts of Africa and South America experienced 20 times more records than expected.
The high number of records in the tropics is because these areas normally experience a small temperature variance, even though the trend in temperature rise in the region is relatively low, Rahmstorf explained. The Arctic also has a high record ratio, but this is due to its larger temperature trend.
Rahmstorf’s analysis showed that the increase in heat extremes can be explained by a simple stochastic model - a linear trend of increasing temperature combined with uncorrelated noise.
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