Eyler IBMYP 6th-8th Science

Researchers
studying long-term changes in sea temperatures said they now expect a
“lull” for up to a decade while natural variations in climate cancel
out the increases caused by man-made greenhouse gas emissions.

	Melting icebergs: The study predicts the IPCC’s 0.3ºC temperature rise for the next decade may not happen

The
average temperature of the sea around Europe and North America is
expected to cool slightly over the decade while the tropical Pacific
remains unchanged.

This would mean that the 0.3°C
global average temperature rise which has been predicted for the next
decade by the UN’s Intergovernmental Panel on Climate Change may not
happen, according to the paper published in the scientific journal
Nature.

However, the effect of rising fossil fuel
emissions will mean that warming will accelerate again after 2015 when
natural trends in the oceans veer back towards warming, according to
the computer model.

Noel Keenlyside of the Leibniz
Institute of Marine Sciences, Kiel, Germany, said: “The IPCC would
predict a 0.3°C warming over the next decade. Our prediction is that
there will be no warming until 2015 but it will pick up after that.”

He
stressed that the results were just the initial findings from a new
computer model of how the oceans behave over decades and it would be
wholly misleading to infer that global warming, in the sense of the
enhanced greenhouse effect from increased carbon emissions, had gone
away.

The IPCC currently does not include in its
models actual records of such events as the strength of the Gulf Stream
and the El Nino cyclical warming event in the Pacific, which are known
to have been behind the warmest year ever recorded in 1998.

Today’s
paper in Nature tries to simulate the variability of these events and
longer cycles, such as the giant ocean “conveyor belt” known as the
meridional overturning circulation (MOC), which brings warm water north
into the North East Atlantic.

This has a 70 to
80-year cycle and when the circulation is strong, it creates warmer
temperatures in Europe. When it is weak, as it will be over the next
decade, temperatures fall. Scientists think that variations of this
kind could partly explain the cooling of global average temperatures
between the 1940s and 1970s after which temperatures rose again.

Writing
in Nature, the scientists said: “Our results suggest that global
surface temperature may not increase over the next decade, as natural
climate variations in the North Atlantic and tropical Pacific
temporarily offset the projected anthropogenic [manmade] warming.”

The
study shows a more pronounced weakening effect than the Met Office’s
Hadley Centre, which last year predicted that global warming would slow
until 2009 and pick up after that, with half the years after 2009 being
warmer than the warmest year on record, 1998.

Commenting
on the new study, Richard Wood of the Hadley Centre said the model
suggested the weakening of the MOC would have a cooling effect around
the North Atlantic.

“Such a cooling could
temporarily offset the longer-term warming trend from increasing levels
of greenhouse gases in the atmosphere.

“That
emphasises once again the need to consider climate variability and
climate change together when making predictions over timescales of
decades.”

But he said the use of just sea surface
temperatures might not accurately reflect the state of the MOC, which
was several miles deep and dependent on factors besides temperatures,
such as salt content, which were included in the Met Office Hadley
Centre model.

If the model could accurately
forecast other variables besides temperature, such as rainfall, it
would be increasingly useful, but climate predictions for a decade
ahead would always be to some extent uncertain, he added.