Climatologist
Schneider meets with
Clinton, Gore
Global warming is real,
seven scientists warned President Clinton and Vice
President Gore in a public briefing on July 24. The
scientists were Stanford climatologist Steve Schneider;
Nobel Laureates Sherwood Rowland of the University of
California-Irvine and Mario Molina of MIT, discoverers of
the atmospheric ozone hole; Nobel laureate Henry Kendall
of MIT, head of the Union for Concerned Scientists;
ecologist Jane Lubchenco of Oregon State University, past
president of the American Association for the Advancement
of Science; infectious disease expert Robert Shope of the
University of Texas; and energy expert John Holdren of
Harvard.
They warned that global
warming and the greenhouse effect are real phenomena, and
that the potential impacts could include dramatic changes
in natural systems ranging from the inundation of the
Everglades by rising sea level to the introduction of
disease-carrying insects to northern climates. Kendall
argued that even if the United States has the resources
to protect its croplands from the effects of climate
change, the potential loss of food crops in developing
countries makes this a national security issue as well as
an environmental one.
Following are
Schneider's remarks in the briefing:
It is important for us to
address the question: So what if the climate changes? How
much would disruption of the expected climate disrupt our
economy?
We've already heard [from
previous speakers] that the Earth's surface temperature
has risen about 1 F since the 19th century. We've been
told about the potential for further warming of several
degrees to cause ecological disruption. But the tough
economic political, really question is, How much is
our stewardship for nature worth? Scientists have
published hundreds of papers on the potential impacts of
projected climatic changes, estimating damages that
typically range from nothing to catastrophic.
To try to sort out some of
this confusion, Yale economist William Nordhaus asked 19
economists, technologists and natural scientists who were
familiar with the scores of studies of so-called
"climate damages" to estimate this as a
percentage of lost gross domestic product (GDP) for the
world. For a hypothetical scenario of 3 C warming by [the
year] 2100, the group he referred to as mainstream
economists' best guess was about a 1 percent GDP loss
with fairly large uncertainty. The natural scientists
estimated 10 times greater damage but with even
greater uncertainty. Nordhaus quipped that those who know
the most about the economy were only modestly worried,
whereas I countered that those who know the most about
nature are more seriously concerned.
Part of that difference in
these professionals' world views is the higher value that
natural scientists put on nature's unpriced services,
like waste recycling or flood control or biotic
diversity. Economists are more optimistic that humans can
invent substitutes for such ecological services. But
suppose the economists are right: even 1 percent of world
GDP lost is, in today's terms, some $200 billion!
Where do such dollar
values come from? I'll give two examples: sea level rise
and hydrological extremes.
First, to sea level.
Hurricane Andrew caused unprecedented losses, about $40
billion. Before 1987 no weather casualty was greater than
$1 billion, but since then several have caused tens of
billions [in losses] and the insurance industry is
understandably very alarmed. Although there is some
theoretical reasoning to expect that warmer ocean
temperatures could produce stronger storms, this is
controversial and no one can credibly attribute some
percentage of Andrew's damage to global warming. But we
do know that sea levels are about 4 to 10 inches higher
than a century ago, which means that any storm, natural
or enhanced by global warming, will have an accompanying
storm surge that penetrates farther inland and creates
greater damages.
Typical global warming
scenarios include projections for a 1/2-foot to 3-foot
greater sea level rise over the next 100 years. Those
rises clearly will pose costs and risks to hundreds of
millions of coastal dwellers around the world and even
to the existence of some island states.
Now, to hydrological
extremes. By hydrological extremes I mean droughts and
floods. Are the many costly floods that occurred across
the United States over the past five years, or the
droughts in 1988, or the heat wave in 1995 that killed
hundreds of vulnerable elderly people in Chicago, merely
two "snake eyes" in a row from a perverse
nature, or, rather, are we "loading the climate
dice"?
How could humans be
involved in the weather act? First, some theory. Since we
add heat-trapping gases like carbon dioxide to the
atmosphere, which, in turn, add energy to the Earth's
surface, some of that energy will be used to evaporate
water no one who is knowledgeable disputes that. More
evaporation globally means more rainfall globally.
Thus, when the atmosphere configures itself for locally
heavy rains, more evaporation means heavier rains, on
average. Likewise, as farmers or lawn waterers know, when
the atmosphere is in a drier mode, higher temperatures
suck more water from the soils. Taken together, these
physical arguments provide the rationale for forecasting
increased droughts and floods from global warming. But
this is physical reasoning, not proof, which reminds me
of the old scientific cliché: In God we trust, but for
the rest of us, please show some data!
Now to some data. Tom Karl
and his colleagues at the National Climate Center in
Asheville, N.C. have analyzed thousands of weather
stations in the U.S. over the past century and found
about a 10 percent increase in precipitation in the
United States since 1910. More significantly, most of
this increase occurred in the top 10th percentile of
extreme daily rainfall events that is, the "gully
washers" that insurance companies fear. While these
observations are consistent both with theory and climate
model predictions, and thus are strong circumstantial
evidence for a global warming impact, certain proof will
take a few more decades of performing this unplanned
experiment on "Laboratory Earth."
Finally, in a system as
complex as the earth-atmosphere- ocean-ice-biosphere
system what scientists call a "non-linear"
system we cannot have precise forecasts that are
credible. But, as the Intergovernmental Panel on Climate
Change noted in concluding its 1995 assessment report,
"When rapidly forced, non-linear systems are
especially subject to unexpected behavior." My free
translation of this concern is that reducing the pressure
that humans put on nature is an insurance policy against
"nasty surprises."
In summary, my view of the
current balance of evidence is metaphorically that the
canary in the cage is starting to quiver. Whether that
shiver is from breathing dangerous air will become
increasingly clear if we continue to accelerate our use
of the atmosphere as an unpriced sewer. SR
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