Uh oh!

[Roger Baker]

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Now we've done it. We may have just gone and screwed up the weather
so bad it may bite us on the butt no matter what we do now. The ocean
currents are like giant conveyer belts for heat and cold and they seem =
to
flip on and off due to gradual changes like global warming in ways we
don't understand until it happens.

But maybe not, if we're lucky. Live and learn, right? At least when it
happens we'll know why. -- Roger

                   ***********************************=09


http://www.nytimes.com/2001/12/12/science/12CLIM.html


December 12, 2001
Drastic Shifts in Climate Are Likely, Experts Warn

By KENNETH CHANG

The vast reshaping of the environment by modern civilization raises the
chances of sudden and drastic upheavals in the climate, a panel of
experts warns.

In a report released yesterday in Washington by the National Research
Council, the research arm of the National Academy of Sciences, a panel
of 11 scientists examined the possibility of abrupt climate change, in
which small events can bring on rapid and great consequences.

Dr. Richard B. Alley, a professor of geosciences at Pennsylvania State
University and chairman of the committee, compared abrupt climate
change to a light switch, while gradual climate =97 what most=20
climatologists
study =97 is like a light dimmer. Press upward on a dimmer, and the =
light
brightens a little. Press more, and the light brightens more. With a=20
switch,
press lightly and nothing happens. Press hard enough, and the light=20
abruptly
turns on.

"What the research shows is that there are switches as well as dimmers =
in
Earth's system," Dr. Alley said.

The scientists do not foresee any imminent changes, and the report=20
advises
that the public "not be fatalistic about the threats." The panel=20
recommends
further research to understand the mechanisms that can cause the sudden
changes.

Most of the report focuses on abrupt changes that occurred naturally,=20
long
before humans dominated the landscape. One prominent example is a period
12,800 years ago known as the Younger Dryas cold interval. The climate=20=

had
almost completely recovered from the last ice age, but then average
temperatures dropped 10 degrees or more and remained cold for more than
1,000 years. Then the Earth abruptly warmed again, perhaps 15 degrees in
a decade. By contrast, the warming of the Earth in the last century was =
1
degree.

Although the sudden shifts occur naturally, the changes in the=20
environment,
including flooding the atmosphere with carbon dioxide or cutting swaths=20=

of
rain forests, could act as a final push, the scientists said. "The=20
harder you
push, the more likely you are to cross a threshold," Dr. Alley said. "We=20=

are
likely to be surprised."

Most climate studies like those that look at global warming and its=20
links to
carbon dioxide emissions have examined changes that emerge gradually
and steadily over decades or centuries.

At the meeting of the American Geophysical Union yesterday in San
Francisco, scientists presented computer simulations indicating that a=20=

rise
in carbon dioxide levels would lengthen the time that a low-pressure=20
weather
system hovered over the North Pole and a high-pressure air mass over the
Atlantic.

That pattern tends to blow in warm air from the Atlantic into Europe,=20
potentially
leading to wetter and warmer winters over the coming decades. But that=20=

gradual
shift to warmer and wetter winters may also cause an abrupt climate=20
change.

Some climate models predict that the increased rainfall may weaken, or=20=

perhaps
even stop, the Atlantic currents that carry warm water northward from=20
the tropics
and may plunge Europe into a new ice age. Other models predict no=20
effects. The
Younger Dryas may have been caused by the turning off of the northward=20=

currents
and may have ended when the currents suddenly resumed.

"It leaves open the question of could we be pushing the variability one=20=

way or
another," said Dr. John M. Wallace, a professor of atmospheric sciences=20=

at the
University of Washington and another panel member. "There are a lot of=20=

ifs."

The report also reviews research on regional temporary shifts like the=20=

1930's Dust
Bowl drought. Although the drought seems to have occurred naturally,=20
soil erosion
caused by farming may have prolonged it.


--Apple-Mail-2--135484660
Content-Transfer-Encoding: quoted-printable
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	charset=WINDOWS-1252

<fontfamily><param>Geneva</param>Now we've done it. We may have just
gone and screwed up the weather

so bad it may bite us on the butt no matter what we do now. The ocean=20

currents are like giant conveyer belts for heat and cold and they seem
to=20

flip on and off due to gradual changes like global warming in ways we=20

don't understand until it happens.

=20

But maybe not, if we're lucky. Live and learn, right? At least when it

happens we'll know why. -- Roger


                  ***********************************=09

<underline><color><param>0000,0000,6666</param>         =20

</color></underline>

http://www.nytimes.com/2001/12/12/science/12CLIM.html

     =20


December 12, 2001

Drastic Shifts in Climate Are Likely, Experts Warn


By KENNETH CHANG


The vast reshaping of the environment by modern civilization raises
the=20

chances of sudden and drastic upheavals in the climate, a panel of=20

experts warns.


In a report released yesterday in Washington by the National Research=20

Council, the research arm of the National Academy of Sciences, a panel=20=


of 11 scientists examined the possibility of abrupt climate change, in=20=


which small events can bring on rapid and great consequences.


Dr. Richard B. Alley, a professor of geosciences at Pennsylvania State=20=


University and chairman of the committee, compared abrupt climate=20

change to a light switch, while gradual climate =97 what most
climatologists=20

study =97 is like a light dimmer. Press upward on a dimmer, and the
light=20

brightens a little. Press more, and the light brightens more. With a
switch,=20

press lightly and nothing happens. Press hard enough, and the light
abruptly=20

turns on.


"What the research shows is that there are switches as well as dimmers
in=20

Earth's system," Dr. Alley said.


The scientists do not foresee any imminent changes, and the report
advises=20

that the public "not be fatalistic about the threats." The panel
recommends=20

further research to understand the mechanisms that can cause the
sudden=20

changes.


Most of the report focuses on abrupt changes that occurred naturally,
long=20

before humans dominated the landscape. One prominent example is a
period=20

12,800 years ago known as the Younger Dryas cold interval. The climate
had=20

almost completely recovered from the last ice age, but then average=20

temperatures dropped 10 degrees or more and remained cold for more
than=20

1,000 years. Then the Earth abruptly warmed again, perhaps 15 degrees
in=20

a decade. By contrast, the warming of the Earth in the last century
was 1=20

degree.


Although the sudden shifts occur naturally, the changes in the
environment,

including flooding the atmosphere with carbon dioxide or cutting
swaths of=20

rain forests, could act as a final push, the scientists said. "The
harder you=20

push, the more likely you are to cross a threshold," Dr. Alley said.
"We are=20

likely to be surprised."


Most climate studies like those that look at global warming and its
links to=20

carbon dioxide emissions have examined changes that emerge gradually=20

and steadily over decades or centuries.=20


At the meeting of the American Geophysical Union yesterday in San=20

Francisco, scientists presented computer simulations indicating that a
rise=20

in carbon dioxide levels would lengthen the time that a low-pressure
weather=20

system hovered over the North Pole and a high-pressure air mass over
the=20

Atlantic.


That pattern tends to blow in warm air from the Atlantic into Europe,
potentially=20

leading to wetter and warmer winters over the coming decades. But that
gradual=20

shift to warmer and wetter winters may also cause an abrupt climate
change.


Some climate models predict that the increased rainfall may weaken, or
perhaps=20

even stop, the Atlantic currents that carry warm water northward from
the tropics=20

and may plunge Europe into a new ice age. Other models predict no
effects. The=20

Younger Dryas may have been caused by the turning off of the northward
currents=20

and may have ended when the currents suddenly resumed.


"It leaves open the question of could we be pushing the variability
one way or=20

another," said Dr. John M. Wallace, a professor of atmospheric
sciences at the=20

University of Washington and another panel member. "There are a lot of
ifs."


The report also reviews research on regional temporary shifts like the
1930's Dust=20

Bowl drought. Although the drought seems to have occurred naturally,
soil erosion=20

caused by farming may have prolonged it.


</fontfamily>=

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