HEN several eminent scientists returned
recently from a tourist cruise to the North Pole aboard a Russian
icebreaker and reported finding water, not ice, at the top of the
world, the image resonated far and wide, providing a call to arms
for scientists and environmentalists who for years had been
trying to convince politicians and the public that heat-trapping
gases from tail pipes, power plants, even methane-belching
cattle, could disrupt the climate.
But on second look,
things were not nearly so simple. Although arctic experts said
there were many signs of warming, including a thinning and
shrinking of the polar ice cap, there was no way to link a patch
of sun- dappled water at the pole to climate change.
So
the question of what is happening to climate — and whether people
or natural forces are to blame — returned to the realm of
nuanced, statistical fuzziness, where it has been for nearly 20
years.
What a moment to lose potential clarion calls.
Hundreds of negotiators from industrialized countries are to
convene this week in Lyon, France, and again in late November in
The Hague to try to firm up ways to cut emissions of greenhouse
gases under a 1997 climate treaty called the Kyoto Protocol. The
treaty was signed by the United States and 84 other countries but
is in danger of falling apart because of disagreements over how
to make and measure cuts.
Most climate experts are certain
that global warming is real and that it threatens ecology and
human prosperity, and a growing number say it is well under way.
But policy makers, always eager for black and white, have once
again found science offering shades of gray.
Indeed,
global warming is a classic example of the persistent mismatch
between the language of science and the needs of policy.
Science operates by steadily chipping away at ideas through
experiments or observations, eventually revealing truths, but
often obliquely — by eliminating what is not true. The bigger the
idea, the harder it often is to verify with precision. The result
is persistent debate, whether the issue is how to manage forests
to reduce wildfires, how to set limits for chemicals in food to
prevent cancer, or — in this case — how to figure out whether
people are dangerously fiddling with the global
thermostat.
But before policy makers can try to sell
potentially costly or difficult solutions, say, taxing fossil
fuels, they need to build a clear and compelling case that strong
action is called for.
The lesson in all of this,
according to climate scientists — some of whom think humanity is
already in big trouble — is that no one should expect some alarm
bell to start ringing to summon societies to take action.
The evidence is subtle and complex, and probably will be so for a
long time to come, said Jerry D. Mahlman, who is retiring as
director of the federal Geophysical Fluid Dynamics Laboratory in
Princeton, N.J. "This is going to be incremental forever," he
said.
Those increments continue to add up, he and other
climate experts said. Past climate ups and downs mostly mesh well
with natural variations in the brightness of the sun or the
cooling effect of parasol-like plumes of particles spewed by big
volcanoes. But the recent warming, according to several recent
studies, only correlates well with one thing: the buildup of
carbon dioxide, methane and the other greenhouse gases.
Hints that warming is being caused by emissions from industry and
other human activities have been extracted from air bubbles
trapped in ancient ice, from variations in tree rings, from the
quick retreat of alpine glaciers. Thermometers dropped deep in
the ocean and in holes bored in permafrost show warming patterns
that do not match up with natural influences like changes in the
sun's brightness.
Still, the subtleties have
allowed warming skeptics ample opportunity to challenge the idea.
Some, like Richard S. Lindzen, a meteorologist at the
Massachusetts Institute of Technology, have built durable
counterarguments, saying the links connecting the earth's oceans,
air and "cryosphere," its frozen places, are impossible to
elucidate with sufficient confidence to predict much beyond next
week's weather.
In an interview, Dr. Lindzen acknowledged
the arctic warming trend and slight global warming measured in
the last century, but said it all is well within the realm of
natural variation or measurement error — and not yet within our
power to understand.
"This is a field that was in a
primitive state when it assumed a policy importance a few years
ago," Dr. Lindzen said. "Suddenly we've declared thousands of
people in a primitive field as world experts, and they're trying
to have their day." And reports last week that boats had
traversed the normally frozen Northwest Passage and northern
rivers and lakes were freezing later and thawing earlier were
countered with the response that this seeming meltdown could
still be ascribed to natural wiggles in temperature or ocean
currents.
But most scientists, including some who work
with Dr. Lindzen at M.I.T., say the balance of data has shifted
firmly toward a conclusion that people, through their impact on
the atmosphere, are influencing climate now and will have even
more impact in coming years.
Somehow, many experts say,
if the threat is to be countered, societies will have to figure
out a way to act in the face of gray uncertainty, to deal
aggressively with a problem that lacks the attributes of a
crisis. That is no easy task.
Dr. Mahlman has pretty much
given up on that hope, saying that many countries, including the
United States, have essentially decided that the focus is going
to be on painless, low-cost fixes like growing trees to sop up
the most common greenhouse gas, carbon dioxide, and on adapting
to coming warming instead of countering it.
"We just
don't want to face up to it," he said, adding that people do not
want to change their lifestyle or the economy "for the sake of
avoiding future costs."
He and others stress that the real
challenge with global warming and similar issues is that, by the
time the impact becomes too clear to debate, it will be far too
late to do anything about it.
