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Climate Change
Already Affecting the Global Environment, Two Reports Say
By Matt Crenson
Associated Press, November 15, 2004
Global warming has had little
noticeable impact in Washington, D.C.
Politicians in the nation's capital have been reluctant to set limits on
the
carbon dioxide pollution that is expected to warm the planet by 4 to 7
degrees Fahrenheit during the next century, citing uncertainty about the
severity of the threat.
But that uncertainty may have
shrunk somewhat with the release last week of
two scientific reports suggesting that global warming is not just a
hypothetical possibility, but a real phenomenon that has already started
transforming especially sensitive parts of the globe.
Overall, the reports say,
Earth's climate has warmed by about 1 degree
Fahrenheit since 1900. In the Arctic, where a number of processes amplify
the warming effects of carbon dioxide, most regions have experienced a
temperature rise of 4 to 7 degrees in the last 50 years.
That warmth has reduced the
amount of snow that falls every winter, melted
away mountain glaciers and shrunk the Arctic Ocean's summer sea ice cover
to
its smallest extent in millennia, according to satellite measurements.
Swaths of Alaskan permafrost are thawing into soggy bogs, and trees are
moving northward at the expense of the tundra that rings the Arctic Ocean.
These changes seriously threaten
animals such as polar bears, which live and
hunt on the sea ice. The bears have already suffered a 15 percent decrease
in their number of offspring and a similar decline in weight over the past
25 years. If the Arctic sea ice disappears altogether during the summer
months, as some researchers expect it will by the end of the century,
polar
bears have little chance of survival.
Things are less serious in the
lower 48, where the effects of climate change
have been more subtle. In much of the United States, spring arrives about
two weeks earlier than it did 50 years ago. Tropical bird species have
appeared in Florida and along the Gulf Coast. Species such as Edith's
checkerspot, a butterfly native to western North America, have started
dying
out at the southern reaches of their ranges.
"Responses to climate change are
being seen across the U.S.A," said Camille
Parmesan, a biologist at the University of Texas in Austin. She is the
co-author, with Hector Galbraith of the University of Colorado in Boulder,
of "Observed Impacts of Global Climate Change in the U.S." The report was
released Tuesday by the Pew Center on Global Climate Change, a
non-partisan
but not disinterested research organization dedicated to providing sound
scientific information about global warming.
Parmesan and Galbraith
acknowledge that nothing in the report would strike
the average person as particularly alarming. They also allow that some of
the past century's warming might have happened even if humans hadn't been
pumping carbon dioxide into the atmosphere. But they argue that the
changes
they describe should be taken as a "very clear signal" that climate change
will have significant effects in coming decades.
"The canaries in the coalmine
are squawking, and we should absolutely take
that seriously," Galbraith said.
The Bush administration has
argued that not enough is known about climate
change to justify major efforts at forestalling or preventing future
warming.
The Arctic report, released
Monday, was commissioned by the Arctic Council,
an international commission of eight countries, including the United
States,
and six indigenous groups. It was written by a team of 300 scientists.
"The report will be a valuable
contribution to the literature on potential
regional impacts of climate change, and the United States government will
take its findings into account as it continues to review the science,"
State
Department spokesman Richard Boucher said in a statement released Tuesday.
The United States faces a
potential showdown with other members of the
Arctic Council on Nov. 24, when representatives of the organization's
members are scheduled to meet in Iceland to consider climate change policy
recommendations.
The atmospheric concentration of
carbon dioxide has risen from 280 parts per
million in 1800 to 380 parts per million today due to the combustion of
fossil fuels. Carbon dioxide causes warming because it heats up more when
exposed to sunlight compared to other atmospheric gases.
Scientists have always expected
the Arctic to respond earlier and more
intensely than other regions to the buildup of carbon dioxide in the
atmosphere, thanks to several phenomena that make the far north especially
sensitive to climate perturbations. When warmer temperatures melt snow,
for
example, the bare ground that is exposed absorbs more heat than the white
surface did, causing yet more warming. A similar thing happens when sea
ice
melts, exposing open water.
In the past three Septembers the
Arctic sea ice has melted back 12 percent
to 15 percent beyond its normal minimum extent.
"It almost suggests that maybe
we're about to reach a threshold beyond which
the sea ice may not be able to recover," said Mark Serreze of the National
Snow and Ice Data Center in Boulder, Colo.
Ice in the interior of the
Arctic pack normally remains frozen from year to
year, growing thicker with each season. But the recent increase in melting
has eaten into much of that multi-year ice. So while the Arctic Ocean
still
freezes over each winter, more of the solid cover now consists of thin
single-year ice that melts every spring.
The Arctic is also particularly
sensitive to warming because its plants and
soil hold less water than more temperate environments. That means more
energy reaching the ground is dedicated to heating the surface instead of
evaporating water.
The atmosphere is thinner in the
Arctic than it is farther south, which also
intensifies warming. And while temperate zones shed some of their extra
heat
by shipping it north in ocean currents and meteorological fronts, the
Arctic
is the end of the line in that respect.
A small minority of scientists
remains unconvinced that increasing
atmospheric carbon dioxide can be held responsible for the recent warming,
arguing that natural variability explains most if not all of the trend.
"It's very complicated and I
believe people who claim they understand...
are just overestimating drastically their ability to do science," Chylek
said.
Scientists aren't the only ones
who have noticed the Arctic warming trend.
Inuit hunters in Canada and Saami reindeer herders in Finland have
detected
shifts in the migratory behavior of animals. In some cases, people whose
elders taught them decades ago how to forecast storms from wind patterns
and
cloud formations have lost their predictive abilities to new weather
patterns.
"One of the unique things about
Arctic communities is how much they're tied
to the land, and that's why this is such a big deal for them," said
Harvard
University geographer Shari Fox Gearheard.
Farther south, where the changes
have been far less extreme and most people
live far removed from the subtleties of their climate, a warmer world
remains a hypothetical realm of scientists and environmentalists. But the
latest reports suggest that in some of the world's more populated places,
astute observers may soon begin to noticing that the climate is changing.
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Associated Press. All Rights Reserved.
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