Global warming has increased monthly heat records by a factor of 5
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| climateark.org |
Monthly
temperature extremes have become much more frequent, as measurements from
around the world indicate. On average, there are now five times as many record-breaking
hot months worldwide than could be expected without long-term global warming,
shows a study now published in Climatic Change. In parts of Europe, Africa and
southern Asia the number of monthly records has increased even by a factor of
ten. 80 percent of observed monthly records would not have occurred without
human influence on climate, concludes the authors-team of the Potsdam Institute
for Climate Impact Research (PIK) and the Complutense University of Madrid.
"The last decade brought unprecedented heat waves; for instance in the US
in 2012, in Russia in 2010, in Australia in 2009, and in Europe in 2003,"
lead-author Dim Coumou says. "Heat extremes are causing many deaths, major
forest fires, and harvest losses -- societies and ecosystems are not adapted to
ever new record-breaking temperatures." The new study relies on 131 years
of monthly temperature data for more than 12,000 grid points around the world,
provided by NASA. Comprehensive analysis reveals the increase in records.
The researchers developed a robust statistical model that
explains the surge in the number of records to be a consequence of the
long-term global warming trend. That surge has been particularly steep over the
last 40 years, due to a steep global-warming trend over this period.
Superimposed on this long-term rise, the data show the effect of natural
variability, with especially high numbers of heat records during years with El
Niño events. This natural variability, however, does not explain the overall
development of record events, found the researchers.
Natural variability does not explain the overall development of
record events
If global warming continues, the study projects that the number
of new monthly records will be 12 times as high in 30 years as it would be
without climate change. "Now this doesn't mean there will be 12 times more
hot summers in Europe than today -- it actually is worse," Coumou points
out. For the new records set in the 2040s will not just be hot by today's
standards. "To count as new records, they actually have to beat heat
records set in the 2020s and 2030s, which will already be hotter than anything
we have experienced to date," explains Coumou. "And this is just the
global average -- in some continental regions, the increase in new records will
be even greater."
"Statistics alone cannot tell us what the cause of any
single heat wave is, but they show a large and systematic increase in the
number of heat records due to global warming," says Stefan Rahmstorf, a
co-author of the study and co-chair of PIK's research domain Earth System
Analysis. "Today, this increase is already so large that by far most
monthly heat records are due to climate change. The science is clear that only
a small fraction would have occurred naturally."
Source: Potsdam Institute for Climate Impact Research (PIK)
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