Global warming stretches subtropical boundaries
Roger Coppock
12:40 26 May 2006
NewScientist.com news service
Jeff Hecht
The atmosphere is warming faster in subtropical areas - around 30°
north and south of the equator - than anywhere else in the world,
according to a study of more than 25 years of satellite data. And the
process appears to be driven by climate change.
Researchers analysed the tropical air circulation pattern - which
brings rain to the equator and dries the subtropics - and found that
this climate belt has expanded by about 1° of latitude, or about 70
miles, towards both the north and south poles over the past 27 years.
This in turn means that the north and south jet streams - the rivers
of fast-moving air that form the boundaries between warm tropical air
and cold polar air - have also moved correspondingly closer to each
pole.
This worrying new feature of global warming could cause deserts to
expand into heavily populated urban areas and see a desert-like climate
encroach upon Europe, the researchers say. And the change could expand
arid zones further from the equator to mid-latitude regions, possibly
cutting winter rain and snowfall in the Alps, the Mediterranean and
south-western Australia.
Sahara spread
"The jet streams mark the edge of the tropics so, if they are moving
poleward, that means the tropics are getting wider," says John Wallace,
who took part in the study at the University of Washington in Seattle,
US.
"If they move another 2° to 3° poleward in this century, very dry
areas such as the Sahara desert could expand further towards the pole,
perhaps by a few hundred miles," he adds.
The researchers used evidence from satellite measurements of
temperatures in the lower atmosphere from the start of 1979, through to
the end of 2005. It showed that the lower atmosphere warmed most over
that period, at latitudes of 15° to 45° in both hemispheres.
The warming raises air pressure, affecting air circulation between
those latitudes and the equator, explains team member Thomas Reichler,
at the University of Utah, US.
[ . . . ]
The rest:
http://www.newscientist.com/article/dn9229-global-warming-stretches-subtropical-boundaries.html
=-=-=-=-=-=-=-=-=-=-=
Science 26 May 2006:
Vol. 312. no. 5777, p. 1179
DOI: 10.1126/science.1125566
Brevia
Enhanced Mid-Latitude Tropospheric Warming in Satellite Measurements
Qiang Fu,1,2* Celeste M. Johanson,1 John M. Wallace,1 Thomas Reichler3
The spatial distribution of tropospheric and stratospheric temperature
trends for 1979 to 2005 was examined, based on radiances from
satellite-borne microwave sounding units that were processed with
state-of-the-art retrieval algorithms. We found that relative to the
global-mean trends of the respective layers, both hemispheres have
experienced enhanced tropospheric warming and stratospheric cooling in
the 15 to 45° latitude belt, which is a pattern indicative of a
widening of the tropical circulation and a poleward shift of the
tropospheric jet streams and their associated subtropical dry zones.
This distinctive spatial pattern in the trends appears to be a robust
feature of this 27-year record.
1 Department of Atmospheric Sciences, University of Washington,
Seattle, WA 98195, USA.
2 College of Atmospheric Sciences, Lanzhou University, Lanzhou, Gansu,
730000, China.
3 Department of Meteorology, University of Utah, 135 S 1460 E, Room 819
(WBB), Salt Lake City, UT 84112-0110, USA.
* To whom correspondence should be addressed. E-mail:
q...@atmos.washington.edu
hsg
not only will desertified areas expand toward the poles, but that the
"wet" tropical/equatorial zone will widen also?
hsg
AdamW
been predicted to get wetter due to Global Warming, but the recent
rainfall deficit in the SE (partly caused by increased Atlantic
blocking) was going against that (this wasn't necessarily a conbtrarian
argument). They called 2005 in the UK the year that global warming
forgot. I think it was still above average temps, but that's a bit of a
tangent.
Firstly, my recollection of the increased rainfall was mainly for
winter?
Also, and more pertinently, I was wondering if the "lack" of water in
the south, the poleward movement of the jet shown here (if confirmed),
the above average rainfall in the north and the prediction of greater
rainfall all dovetailed together to form a coherent picture.
It would be interesting to hear from someone who's been following this
stuff more closely, if they have a comment.
William M Connolley
On Mon, 5 Jun 2006, AdamW wrote:
> Recently, someone (I forget who and where) pointed out that the UK had
> been predicted to get wetter due to Global Warming, but the recent
I'm not following this carefully, but I have the impression that the UK is close
to a boundary... continental europe dries; further north wettens; the uk is hard
to say.
-W.
William M Connolley | w...@bas.ac.uk | http://www.antarctica.ac.uk/met/wmc/
Climate Modeller, British Antarctic Survey | (01223) 221479
If I haven't seen further, it's because giants were standing on my shoulders
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AdamW
William M Connolley wrote:
> On Mon, 5 Jun 2006, AdamW wrote:
> > Recently, someone (I forget who and where) pointed out that the UK had
> > been predicted to get wetter due to Global Warming, but the recent
>
> I'm not following this carefully, but I have the impression that the UK is close
> to a boundary... continental europe dries; further north wettens; the uk is hard
> to say.
>
My (recent) reading is, and I haven't found anything detailed on this
yet, is that the drying of Europe and wetting of northern areas is due
to the shifting of the jet. I think the UK affect is dependant on by
how much, and whether there might be any change in the wave pattern of
the jet (this latter bit is complete specualtion on my part). However I
doubt it's as simple as that. It never is. ;-)