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Global increase in record-breaking monthly-mean temperatures

January 22, 2013

springer.com  legalbrief

The last decade has produced record-breaking heat waves in many parts of the world. At the same time, it was globally the warmest since sufficient measurements started in the 19th century. Here we show that, worldwide, the number of local record-breaking monthly temperature extremes is now on average five times larger than expected in a climate with no long-term warming. This implies that on average there is an 80 % chance that a new monthly heat record is due to climatic change. Large regional differences exist in the number of observed records. Summertime records, which are associated with prolonged heat waves, increased by more than a factor of ten in some continental regions including parts of Europe, Africa, southern Asia and Amazonia. Overall, these high record numbers are quantitatively consistent with those expected for the observed climatic warming trend with added stationary white noise. In addition, we find that the observed records cluster both in space and in time. Strong El Niño years see additional records superimposed on the expected long-term rise. Under a medium global warming scenario, by the 2040s we predict the number of monthly heat records globally to be more than 12 times as high as in a climate with no long-term warming.

Global warming has caused monthly heat records to increase fivefold in frequency, according to a study by scientists in Germany and Spain.

A report in The Times notes that in parts of Europe, Africa and southern Asia, the frequency of months with record-breaking heat has surged tenfold, according to the study, published last week. The evidence comes from an analysis of 131 years of monthly temperature data, monitored at 12 000 points around the world and stored in a Nasa database. If man-made warming is stripped out of the equation, 80% of the records for hottest months would not have occurred the report notes. ‘The last decade brought unprecedented heat waves, for instance in the US in 2012, Russia in 2010, Australia in 2009 and Europe in 2003,’ Dim Coumou, of the Potsdam Institute for Climate Impact Research near Berlin, is quoted in the report as saying.

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