National Geographic / September, 2004
Global warming can seem too remote to worry about, or
too uncertain – something projected by the same computer techniques that often
can't get next week's weather right. On a raw winter day you might think that a
few degrees of warming wouldn't be such a bad thing anyway. And no doubt about
it: Warnings about climate change can sound like an environmentalist scare
tactic, meant to force us out of our cars and cramp our lifestyles.
Comforting thoughts, perhaps. But turn to "GeoSigns," the
first chapter in our report în the
changing planet. The Earth has some unsettling news.
From
Alaska to the snowy peaks of the Andes the world is heating up right now, and
fast. Globally, the temperature is up 1°F over the past century, but some of
the coldest, most remote spots have warmed much more. The results aren't
pretty. Ice is melting, rivers are running dry, and coasts are eroding,
threatening communities. Flora and fauna are feeling the heat too, as you'll
read in "EcoSigns." These aren't projections; they are facts on the
ground.
The changes are happening largely out of sight. But they shouldn't be out of mind, because they are omens of what's in store for the rest of the planet.
Wait a minute, some doubters say. Climate is notoriously fickle. A thousand
years ago Europe was balmy and wine grapes grew in England; by 400 years ago
the climate had turned chilly and the Thames froze repeatedly. Maybe the
current warming is another natural vagary, just a passing thing?
Don't bet on it, say climate experts. Sure, the natural rhythms of
climate might explain a few of the warming signs you'll read about in the
following pages. But something else is driving the planet-wide fever.
For centuries we've been clearing forests and burning coal, oil, and
gas, pouring carbon dioxide and other heat-trapping gases into the atmosphere
faster than plants and oceans can soak them up (see "The Case of the
Missing Carbon," February 2004). The atmosphere's level of carbon dioxide
now is higher than it has been for hundreds of thousands of years. "We're
now geological agents, capable of affecting the processes that determine
climate," says George Philander, a climate expert at Princeton University.
In effect we're piling extra blankets on our planet.
Human
activity almost certainly drove most of the past century's warming, a landmark
report from the United Nations Intergovernmental Panel on Climate Change (IPCC)
declared in 2001. Global temperatures are shooting up faster than at any other
time in the past thousand years. And climate models show that natural forces,
such as volcanic eruptions and the slow flickers of the sun, can't explain all
that warming.
As CO2 continues to rise, so will the mercury – another 3°F
to 10°F by the end of the century, the IPCC projects. But the warming may not
be gradual. The records of ancient climate described in "TimeSigns"
suggest that the planet has a sticky thermostat. Some experts fear today's
temperature rise could accelerate into a devastating climate lurch. Continuing
to fiddle with the global thermostat, says Philander, "is just not a wise
thing to do."
Already we've pumped out enough greenhouse gases to warm the planet for
many decades to come. "We have created the environment in which our
children and grandchildren are going to live," says Tim Barnett of the
Scripps Institution of Oceanography, We owe it to them to prepare for higher
temperatures and changed weather – and to avoid compounding the damage.
It won't be easy for a world addicted to fossil fuels to limit
emissions. Three years ago the United States spurned the Kyoto Protocol, citing
cost. But even Kyoto would barely slow the rise in heat-trapping gases.
Controlling the increase "would take 40 successful Kyotos," says
Jerry Mahlman of the National Center for Atmospheric Research. "But we've
got to do it."
The signs of warming in the following pages are striking enough, but
they are just a taste of the havoc the next century could bring. Can we act in
time to avert the worst of it? The Earth will tell.
Tim Appenzeller • Senior
Editor, Science
Dennis R. Dimick • Senior
Editor, Environment and Technology