Changing jet streams may alter paths of storms and hurricanes

Changing jet streams may alter paths of storms and hurricanes

Stanford, CA—The Earth’s jet streams, the high-altitude bands of
fast winds that strongly influence the paths of storms and other
weather systems, are shifting—possibly in response to global warming.
Scientists at the Carnegie Institution determined that over a 23-year
span from 1979 to 2001 the jet streams in both hemispheres have risen
in altitude and shifted toward the poles. The jet stream in the
northern hemisphere has also weakened. These changes fit the
predictions of global warming models and have implications for the
frequency and intensity of future storms, including hurricanes.

Cristina
Archer and Ken Caldeira of the Carnegie Institution’s Department of
Global Ecology tracked changes in the average position and strength of
jet streams using records compiled by the European Centre for
Medium-Range Weather Forecasts, the National Centers for Environmental
Protection, and the National Center for Atmospheric Research. The data
included outputs from weather prediction models, conventional
observations from weather balloons and surface instruments, and remote
observations from satellites. The results are published in the April 18
Geophysical Research Letters.

Jet streams twist and turn in a
wide swath that changes from day to day. The poleward shift in their
average location discovered by the researchers is small, about 19
kilometers (12 miles) per decade in the northern hemisphere, but if the
trend continues the impact could be significant. “The jet streams are
the driving factor for weather in half of the globe,” says Archer. “So,
as you can imagine, changes in the jets have the potential to affect
large populations and major climate systems.”

Storm paths in
North America are likely to shift northward as a result of the jet
stream changes. Hurricanes, whose development tends to be inhibited by
jet streams, may become more powerful and more frequent as the jet
streams move away from the sub-tropical zones where hurricanes are born.

The
observed changes are consistent with numerous other signals of global
warming found in previous studies, such as the widening of the tropical
belt, the cooling of the stratosphere, and the poleward shift of storm
tracks. This is the first study to use observation-based datasets to
examine trends in all the jet stream parameters, however.

“At
this point we can’t say for sure that this is the result of global
warming, but I think it is,” says Caldeira. “I would bet that the trend
in the jet streams’ positions will continue. It is something I’d put my
money on.”

###

Contact Ken Caldeira at 650-704-7212, kcaldeira@stanford.edu

For copies of the paper contact the authors

The Carnegie Institution (www.CIW.edu)
has been a pioneering force in basic scientific research since 1902. It
is a private, nonprofit organization with six research departments
throughout the U.S. Carnegie scientists are leaders in plant biology,
developmental biology, astronomy, materials science, global ecology,
and Earth and planetary science. The Department of Global Ecology,
located in Stanford, California, was established in 2002 to help build
the scientific foundations for a sustainable future. Its scientists
conduct basic research on a wide range of large-scale environmental
issues, including climate change, ocean acidification, biological
invasions, and changes in biodiversity.

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