A dose of subjective
opinion may be just what Earth needs, climatologist says
BY MARK SHWARTZ
Few issues in science are
as controversial as global warming.
The debate over climate
change has become so contentious that many experts often
refuse to make far-ranging predictions, choosing instead
to report narrow findings based on a limited set of
available data.
But climatologist Stephen
H. Schneider says that speculation by scientists can be a
good thing -- especially when the future of the planet is
at stake.
"The scientific
community that studies the problem of global warming
should try to answer the difficult questions," says
Schneider, a professor of biological sciences with
Stanford's Institute for International Studies.
The struggle, he adds, is
"how to reconcile the public's need to have an
honest but still subjective assessment, versus the
scientist's penchant for not commenting until all of the
data are in."
For the past five years,
Schneider and Richard H. Moss of the Pacific Northwest
National Laboratory have been working with the United
Nations Intergovernmental Panel on Climate Change. The
IPCC assesses the credibility of scientific research on
global warming, and uses that information to advise world
leaders and policymakers on options for adapting to
climate change -- such as preventing degradation of
forests or reducing the consumption of gasoline and other
fossil fuels.
Schneider and Moss
recently prepared a series of recommendations for how
IPCC members should deal with subjective uncertainties in
the climate change debate. They presented their findings
at the annual American Association for the Advancement of
Science (AAAS) meeting on Feb. 21 in Washington, D.C.
The authors began by
asking AAAS delegates the following questions: "How
often has someone reporting on a difficult problem
exclaimed, 'It's not an exact science, you know'?
"In fact, how many
people really know that science is never 'exact' but
rather an endless series of refinements?"
Schneider and Moss pointed
out that, while scientists strive to be as objective as
possible, "nearly all aspects of interesting global
change projections (like the amount sea levels will rise
and the potential effects this will have on human coastal
settlements) involve subjective probabilities."
Many IPCC scientists are
"simply uncomfortable with the notion that there was
a subjective element to their analyses," but
Schneider and Moss argued that, in the real world, there
is a difference between traditional, objective science
and the more subjective "science for policy."
"'Science for
policy,'" they noted, "involves being
responsive to policymakers' needs for expert judgment at
a particular time, given the information then available.
"Political leaders
want such state-of-the-art subjective assessments -- just
as they do for health, economic and military risks --
even before enough experiments have been performed or
data collected to 'objectively' verify possible
hypotheses."
Schneider and Moss
maintained that "political leaders are not in a
position to judge the likelihood of a certain climate
scenario any more than a patient is competent to judge
which metal should be in the blade of the scalpel used by
her or his surgeon."
"It is more rational
for scientists debating the specifics of a topic in which
they are acknowledged experts to provide their best
judgments based on their assessment of the evidence than
to have policymakers and other users who are less expert
make their own determinations."
It is essential, said
Schneider and Moss, that scientists be consistent and
clear when advising policymakers on the merits of climate
change research. In the past, IPCC experts have issued
reports using a variety of vague expressions like
"almost certain," "probable,"
"likely," "possible,"
"improbable" and "doubtful."
"These terms have not
been carefully -- or quantitatively -- calibrated"
and therefore have been subject to misinterpretation,
observed Schneider and Moss.
They recommended that IPCC
create a glossary of common terms to be used by all
authors so that policymakers, the public and the news
media will have a more precise understanding of the
meaning of words such as "doubtful" or
"unlikely."
The authors also stressed
the importance of providing a clearly defined,
quantitative scale so that probabilistic terms like
"best estimate" would be consistently used in
all IPCC reports.
"If we don't offer a
carefully hedged but nonetheless expert judgment on
global warming, then who's going to do it?"
Schneider asked. "Politicians? Special
interests?" SR
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By Mark Shwartz
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