Heat Waves to Become
Much More Frequent and Severe
Climate
change is set to trigger more frequent and severe heat waves in the next 30
years regardless of the amount of carbon dioxide (CO2) we emit into
the atmosphere, a new study has shown.
Extreme
heat waves such as those that hit the US in 2012 and Australia in 2009 --
dubbed three-sigma events by the researchers -- are projected to cover double
the amount of global land by 2020 and quadruple by 2040.
The
new study, which has been published on 15 August, in IOP Publishing's
journal Environmental Research Letters, finds that in the first
half of the 21st century, these projections will occur regardless of the amount
of CO2 emitted into the atmosphere.
After
then, the rise in frequency of extreme heat waves becomes dependent on the
emission scenario adopted. Under a low emission scenario, the number of
extremes will stabilise by 2040, whereas under a high emission scenario, the
land area affected by extremes will increase by one per cent a year after 2040.
Lead
author of the study, Dim Coumou, from the Potsdam Institute for Climate Impact
Research, said: "We find that up until 2040, the frequency of monthly heat
extremes will increase several fold, independent of the emission scenario we
choose to take. Mitigation can, however, strongly reduce the number of extremes
in the second half of the 21st century."
Under
a high emission scenario, the projections show that by 2100, 3-sigma heat waves
will cover 85 per cent of the global land area and five-sigma heat waves will
cover around 60 per cent of global land.
"A
good example of a recent three-sigma event is the 2010 heat wave in Russia,
which expanded over a large area stretching from the Baltic to the Caspian Sea.
In the Moscow region the average temperature for the whole of July was around
7°C warmer than normal -- it was around 25°C. In some parts, temperatures above
40°C were measured," continued Coumou.
In
their study, Dim Coumou, from the Potsdam Institute for Climate Impact
Research, and Alexander Robinson, from Universidad Complutense de Madrid, used
state-of-the-art climate models to project changes in the trend of heat
extremes under two future warming scenarios -- RCP2.6 and RCP8.5 -- throughout
the 21st century. The historic period was also analysed, and the results showed
that the models can accurately reproduce the observed rise in monthly heat
extremes over the past 50 years.
Co-author
of the study, Alexander Robinson, said: "Our three- and five-sigma
thresholds are defined by the variability a region has experienced in the past,
so the absolute temperatures associated with these types of event will differ
in different parts of the world. Nonetheless these events represent a
significant departure from the normal range of temperatures experienced in a
given region."
According
to the research, tropical regions will see the strongest increase in heat
extremes, exceeding the threshold that is defined by the historic variability
in the specific region. The results show that these changes can already be seen
when analysing observations between 2000 and 2012.
"Heat
extremes can be very damaging to society and ecosystems, often causing
heat-related deaths, forest fires or losses to agricultural production. So an
increase in frequency is likely to pose serious challenges to society and some
regions will have to adapt to more frequent and more severe heat waves already
in the near-term," continued Coumou.
Story Source:
The
above story is based on materials provided by Institute of Physics.
Note: Materials may be edited for content and length. For further
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Journal Reference:
1.
Dim Coumou, Alexander
Robinson. Historic and future increase in the global land area affected
by monthly heat extremes. Environmental Research Letters, 2013;
8 (3): 034018 DOI: 10.1088/1748-9326/8/3/034018
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Institute of Physics (2013, August 15). Heat waves to become much
more frequent and severe. Science Daily. Retrieved August 15, 2013,
from http://www.sciencedaily.com/releases/2013/08/130815084845.htm
