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Asunto:[LEA-Venezuela] cambio climatico global no es problema?
Fecha:Martes, 23 de Octubre, 2001  18:05:06 (-0400)
Autor:Interfaz Amazonica <interfaz @.....net>

cambio climatico global no es problema?
Sorry, esta en ingles...

---------------------------

http://www.sciam.com/2001/1101issue/1101profile.html
Dissent in the Maelstrom
Maverick meteorologist Richard S. Lindzen keeps right on arguing that
human-induced global warming isn't a problem


RICHARD S. LINDZEN:
CLIMATE SKEPTIC
Born in 1940 and grew up in New York City; married with two children.
Degrees from Harvard University; holds the endowed Alfred P. Sloan Professor
of Meteorology chair at M.I.T.
What he would do to global warming research if he held the federal purse
strings: cut funding. "You would no longer have vested interests in the
problem remaining" if funds were scarcer.

KATHLEEN DOHER
Adviser to senators, think tanks and at least some of the president's men,
Richard S. Lindzen holds a special place in today's heated debate about
global warming. An award-winning scientist and a member of the National
Academy of Sciences, he holds an endowed chair at the Massachusetts
Institute of Technology and is the nation's most prominent and vocal
scientist in doubting whether human activities pose any threat at all to the
climate. Blunt and acerbic, Lindzen ill-tolerates naďveté. So it was with
considerable trepidation recently that I parked in the driveway of his
suburban home.

A portly man with a bushy beard and a receding hairline, Lindzen ushered me
into his living room. Using a succession of cigarettes for emphasis, he
explains that he never intended to be outspoken on climate change. It all
began in the searing summer of 1988. At a high-profile congressional
hearing, physicist James E. Hansen of the NASA Goddard Institute for Space
Studies went public with his view: that scientists knew, "with a high degree
of confidence," that human activities such as burning fossil fuel were
warming the world. Lindzen was shocked by the media accounts that followed.
"I thought it was important," he recalls, "to make it clear that the science
was at an early and primitive stage and that there was little basis for
consensus and much reason for skepticism." What he thought would be a couple
of months in the public eye has turned into more than a decade of climate
skepticism. "I did feel a moral obligation," he remarks of the early days,
"although now it is more a matter of being stuck with a role."

It may be just a role, but Lindzen still plays it with gusto. His
wide-ranging attack touches on computer modeling, atmospheric physics and
research on past climate. His views appear in a steady stream of
congressional testimonies, newspaper op-eds and public appearances. Earlier
this year he gave a tutorial on climate change to President George W. Bush's
cabinet.

It's difficult to untangle how Lindzen's views differ from those of other
scientists because he questions so much of what many others regard as
settled. He fiercely disputes the conclusions of this past spring's report
of the Intergovernmental Panel on Climate Change (IPCC)--largely considered
to be the definitive scientific assessment of climate change--and those of a
recent NAS report that reviewed the panel's work. (Lindzen was a lead author
of one chapter of the IPCC report and was an author of the NAS report.) But,
according to him, the country's leading scientists (who, he says, concur
with him) prefer not to wade into the troubled waters of climate change:
"It's the kind of pressure that the average scientist doesn't need." Tom M.
L. Wigley, a prominent climate scientist at the National Center for
Atmospheric Research, says it is "demonstrably incorrect" that top
researchers are keeping quiet. "The best people in the world," he observes,
have contributed to the IPCC report.


----------------------------------------------------------------------------
----

To Lindzen, climate research is "polluted with political rhetoric"; the
science remains weak.

----------------------------------------------------------------------------
----

Lindzen agrees with the IPCC and most other climate scientists that the
world has warmed about 0.5 degree Celsius over the past 100 years or so. He
agrees that human activities have increased the amount of carbon dioxide in
the atmosphere by about 30 percent. He parts company with the others when it
comes to whether these facts are related. It's not that humans have no
effect at all on climate. "They do," he admits, though with as much impact
on the environment as when "a butterfly shuts its wings."

The IPCC report states that "most of the observed warming over the last 50
years" is of human origin. It says that late 20th-century temperatures shot
up above anything the earth had experienced in the previous 1,000 years.
Michael E. Mann, a geologist at the University of Virginia and a lead author
of the IPCC's past-climate chapter, calls the spike "a change that is
inconsistent with natural variability." Lindzen dismisses this analysis by
questioning the method for determining historical temperatures. For the
first 600 years of the 1,000-year chronology, he claims, researchers used
tree rings alone to gauge temperature and only those from four separate
locations. He calls the method used to turn tree-ring width into temperature
hopelessly flawed.

Mann was flabbergasted when I questioned him about Lindzen's critique, which
he called "nonsense" and "hogwash." A close examination of the IPCC report
itself shows, for instance, that trees weren't the sole source of data--ice
cores helped to reconstruct the temperatures of the first 600 years, too.
And trees were sampled from 34 independent sites in a dozen distinct regions
scattered around the globe, not four.

Past climate isn't the only point of divergence. Lindzen also says there is
little cause for concern in the future. The key to his optimism is a
parameter called "climate sensitivity." This variable represents the
increase in global temperature expected if the amount of carbon dioxide in
the air doubles over preindustrial levels--a level the earth is already one
third of the way toward reaching. Whereas the IPCC and the NAS calculate
climate sensitivity to be somewhere between 1.5 and 4.5 degrees C, Lindzen
insists that it is in the neighborhood of 0.4 degree.

The IPCC and the NAS derived the higher range after incorporating positive
feedback mechanisms. For instance, warmer temperatures will most likely
shrink the earth's snow and ice cover, making the planet less reflective and
thus hastening warming, and will also probably increase evaporation of
water. Water vapor, in fact, is the main absorber of heat in the atmosphere.


CLOUD cover over the tropics could reduce global warming--or increase it.
NASA/SPL/PHOTO RESEARCHERS, INC.


But such positive feedbacks "have neither empirical nor theoretical
foundations," Lindzen told the U.S. Senate commerce committee this past May.
The scientist says negative, not positive, feedback rules the day. One
hypothesis he has postulated is that increased warming actually dries out
certain parts of the upper atmosphere. Decreased water vapor would in turn
temper warming. Goddard's Hansen says that by raising this possibility
Lindzen "has done a lot of good for the climate discussion." He hastens to
add, however, "I'm very confident his basic criticism--that climate models
overestimate climate sensitivity--is wrong."

In March, Lindzen published what he calls "potentially the most important"
paper he's written about negative feedback from water vapor. In it, he
concludes that warming would decrease tropical cloud cover. Cloud cover is a
complicated subject. Depending on factors that change by the minute, clouds
can cool (by reflecting sunlight back into space) or warm (by trapping heat
from the earth). Lindzen states that a reduction in tropical cloudiness
would produce a marked cooling effect overall and thus serve as a
stabilizing negative feedback.

But three research teams say Lindzen's paper is flawed. For example, his
research was based on data collected from satellite images of tropical
clouds. Bruce A. Wielicki of the NASA Langley Research Center believes that
the images were not representative of the entire tropics. Using data from a
different satellite, Wielicki and his group conclude, in a paper to appear
in the Journal of Climate, that, on balance, warmer tropical clouds would
have a slight heating, not a cooling, effect.

Looking back at the past decade of climate science, many researchers say
computer models have improved, estimates of past climate are more accurate,
and uncertainty is being reduced. Lindzen is not nearly so sanguine. In his
mind the case for global warming is as poor as it was when his crusade
began, in 1988. Climate research is, he insists, "heavily polluted by
political rhetoric, with evidence remaining extremely weak." To Lindzen,
apparently, the earth will take care of itself.


----------------------------------------------------------------------------
----

By DANIEL GROSSMAN
Daniel Grossman is a freelance writer in Watertown, Mass.




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