Warm
North Atlantic ocean causing UK's wet summers, study shows
Data
points to link between warmer oceans and the change in weather, and
the possibility of a rapid reversal to drier climate
8
October, 2012
The
UK's dismal recent summers can be blamed on a substantial warming of
the North Atlantic ocean in the late 1990s, according to new
scientific research. The shift has resulted in rain-soaked weather
systems being driven into northern Europe, increasing summer rainfall
by about a third.
The
pattern is likely to revert to drier summers and may do so suddenly,
according to Professor Rowan Sutton, at the University of Reading,
who led the work. "I can't guarantee it but it is likely,"
he said. "However we are not sure of the timing, which is what
every one wants to know – but we are working on this now."
Sutton added that when the switch occurs, it could happen as rapidly
as over two to three years.
The
summer of 2012 was the wettest in a century and follows a series of
above average years for summer rainfall. Sutton's team, who published
their study in Nature Geoscience, examined over a century of data and
found that the temperature of the North Atlantic remains above or
below the long term average for decades at a time. The periods of
warmer temperature, the latest of which started in the late 1990s,
were found to correlate with wet summers in Northern Europe and
hotter, drier summers in the Mediterranean. The team used existing
detailed climate simulations to demonstrate a causal link between the
warmer oceans and the change in the weather.
Sutton
said these shifts have been occurring for many hundreds of years, but
that global warming was also having an impact. "It is not now
purely natural or purely a manifestation of human-induced climate
change," he said. "There is lot of evidence to show that
climate change is changing the timing and amplitude of the
temperature changes." For example, he said, the cooler period
from the 1960s to the 1980s occurred when soot and other pollution
from dirty power stations cooled the planet.
The
previous North Atlantic warm phase, which ran from the 1930s to the
1950s, also saw a run of wet summers in the UK, including severe
flooding in August 1948, which closed the east coast mainline railway
for three months, and the Lynmouth floods in August 1952 in which 34
people died.
The
warming of the North Atlantic has been one reason for the record low
in Arctic sea ice this summer. It is possible that the shrinking of
the sea ice is also contributing to poor summers in the UK, as the
exposed ocean waters warm in the sun. However, Sutton said that this
remains to be proven by scientific work that is now underway.
Map:
Europe rainfall
The
warm and cold swings in the North Atlantic affect temperatures, rain
and winds across Europe, Africa and North and South America, and
previous research indicates they are related to changes in ocean
circulation. Other research at Reading University has suggested that
it may in future be possible to predict the warming and cooling
cycles some years ahead.
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