Previous studies have shown that when the jet stream is wavy there
are more episodes of severe cold weather plunging south from the Arctic
into the mid-latitudes, which persist for weeks at a time. But when the
jet stream is flowing strongly from west to east and not very wavy, we
tend to see more normal winter weather in countries within the
Scientists have agreed for the first time that recent severe cold
winter weather in the UK and US may have been influenced by climate
change in the Arctic, suggested a new study.
‘The recent severe cold winter weather in the UK and US may have been influenced by climate change in the Arctic. This finding could improve long-term forecasting of winter weather.’
The research, carried out by an international team of scientists
including the University of Sheffield, has found that warming in the
Arctic may be intensifying the effects of the jet stream's position,
which in the winter can cause extreme cold weather, such as the winter
of 2014/15 which saw record snowfall levels in New York.
Scientists previously had two schools of thought. One group believe
that natural variability in the jet stream's position has caused the
recent severe cold winter weather seen in places such as the Eastern
United States and the UK. The other camp includes scientists who are
finding possible connections between the warming of the Arctic - such as
melting sea ice, warming air temperatures, and rising sea surface
temperatures - and the emerging pattern of severe cold winter weather.
Now, Professor Edward Hanna and Dr Richard Hall from the
University's Department of Geography, together with Professor. James E.
Overland from the US Oceanographic and Atmospheric Administration
(NOAA), have brought together a diverse group of researchers from both
sides of the debate.
The researchers have found that the recent pattern of cold winters
is primarily caused by natural changes to the jet stream's position;
however, the warming of the Arctic appears to be exerting an influence
on cold spells, but the location of these can vary from year to year.
"We've always had years with wavy and not so wavy jet stream winds,
but in the last one to two decades the warming Arctic could well have
been amplifying the effects of the wavy patterns," Professor Hanna said.
He added, "This may have contributed to some recent extreme cold winter
spells along the eastern seaboard of the United States, in eastern
Asia, and at times over the UK (e.g. 2009/10 and 2010/11)."
"Improving our ability to predict how climate change is affecting
the jet stream will help to improve our long-term prediction of winter
weather in some of the most highly populated regions of the world."
"This would be hugely beneficial for communities, businesses, and
entire economies in the northern hemisphere. The public could better
prepare for severe winter weather and have access to extra crucial
information that could help make live-saving and cost-saving decisions."
The study, Nonlinear response of mid-latitude weather to the
changing Arctic, is published in the journal Nature Climate Change
. The research was partly sponsored by the
International Arctic Science Committee (IASC) and the Climate and
Cryosphere (CliC) project of the World Climate Research Program
It further cements the University's position at the forefront of
climate change research and gives geography students at Sheffield access
to the latest innovations in environmental science.