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Floods in Datchet, Berkshire. Britain has had its wettest
winter in 250 years. Photograph: Graham Turner for the Guardian
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UN's World Meteorological
Organisation says recent extremes of heat, cold and rain are almost certainly
interlinked
John Vidalhttp
theguardian.com, Tuesday 25 February 2014 / http://www.theguardian.com/environment/2014/feb/25/world-2014-extreme-weather-events
There have been heatwaves in Slovenia and Australia, snow in
Vietnam and the return of the polar vortex to North America. Britain has had
its wettest winter in 250 years but temperatures in parts of Russia and the
Arctic have been 10C
above normal. Meanwhile, the southern hemisphere has had the warmest start to a
year ever recorded, with millions of people sweltering in Brazilian and
southern African cities.
According to the UN's World Meteorological Organisation
(WMO), which monitors global weather, the first six weeks of 2014 have seen an
unusual number of extremes of heat, cold and rain – not just in a few regions
as might be expected in any winter, but right the way around the world at the
same time, with costly disruptions to transport, power systems and food
production.
"Melbourne, Adelaide and Canberra have all had record
heatwaves, while temperatures in Moscow were 11C above normal. Germany and
Spain were 2C
above normal for January and this month has seen so far six major depressions
develop over the Atlantic," said the WMO in its latest assessment of world
weather.
"Both equatorial and polar regions have experienced
extremes. There has been unusually heavy snowfall; in the southern Alps,
monthly temperatures were extremely high; from eastern Mongolia to eastern
China and in the southern hemisphere, Australia, Argentina and Brazil have
experienced extended heatwaves. The unusually cold weather in the eastern US
coincided with severe storms in Europe," it says.
Some climate scientists argue that there is nothing unusual
in winter global temperature extremes but Omar Baddour, chief of the WMO data
division, says the recent phenomena are almost certainly interlinked, with new
computer models suggesting increased evidence of climate change.
"We need more time to assess whether this is unusual
[on a global level] but if you look at the events in individual regions, like
the heatwave in Australia or the cold in the US, it looks very unusual indeed.
Next month we will publish a major report showing the likelihood of extreme
heatwaves is increased 500% [with climate change]."
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The Chicago skyline and a freezing Lake Michigan. North
America has experienced an 'endless winter' of snow and ice. Photograph: Nam Y.
Huh/AP
There is no connection between northern and southern
hemisphere phenomenon, says Baddour, but the intense cold and heatwaves in the
northern hemisphere appear to be linked by "planetary waves", or
giant meanders in high-altitude winds like jet streams.
"A low pressure in one part of the world may be linked
to a high in another. The two hemispheres are divided by the equator and not
connected but, from a global perspective, climate change affects both. The
global cause [of the extremes] can be the same," he said.
The WMO assessment coincides with exceptionally warm air and
water this month in the Arctic. The sea ice, that forms and melts each year,
would normally be still growing strongly in mid-February, but has dramatically
slowed in the last two weeks and now covers 14.36 million square miles – the
lowest extent ever recorded in February.
"The Arctic is pretty warm everywhere. If I look at
temperature anomalies, there's a huge anomaly over the Barents Sea and Sea of
Okhotsk of about 10C
(above normal) compared to 1981-2010," said Julienne Stroeve, a senior
scientist at the US National Snow and Ice Data Centre at Boulder, Colorado.
"We are living in a time where the climate is changing
quite rapidly. There is reason to expect that the changes in the sea ice will
have large local effects. Further investigation will improve our knowledge of
whether or not the effects of sea ice decline and broader changes in the Arctic
have global effects," said leading US meteorologist Jeff Masters.
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A worker stands next to water markers at Jaguary dam in
Braganca Paulista. This has been the hottest January on record in parts of
Brazil. Photograph: Nacho Doce/Reuters
The first two months of 2014 appear to back up last year's
UN Intergovernmental Panel on Climate Change report report, which stated that
the number, frequency and intensity of hot days and heatwaves was increasing,
along with an increase in the intensity and number of heavy rainfall events.
Bob Ward, policy and communications director at the Grantham
Research Institute at the London School of Economics, said the science linking
weather extremes to climate change was becoming clearer.
"We are seeing the extremes move into new territory.
The pattern of extreme weather events that we have seen across the globe over
the past 12 months bears the unmistakable fingerprint of climate change, with
high temperatures recorded in many parts of the world," he said.
"We are also seeing some unusual phenomenon, such as
the polar vortex in North America, that is bringing unusually cold weather,
which would not be automatically be considered to be due to climate change.
However, there is some evidence that such unexpected surprises are also due to
global warming."
But some climate scientists are cautious about linking
extremes to
climate change. "Looking for a signal of climate change
in short-term weather does not make much scientific sense … There is however
evidence for increasing heatwaves and in some measures, increasing
precipitation," said Roger Pielke Jr, of the Centre for Science and
Technology Policy Research at the University of Colorado.
"Human-caused climate change is real, poses risks and
we should take action in terms of both mitigation and adaptation. [But] extreme
events are a bad place to look for climate signals."
Last year was the sixth warmest on record, according to the
WMO.
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