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 worldwide
wave of extreme weather inflicted at least $90 billion in damage
in 1998, more than in the entire 1980s. Last year was also the
hottest on record. While no single weather event or year proves
humans are warming the planet, a powerful scientific case is
building. Some of the most compelling evidence emerged in just
the past year.
 Greenhouse
gases are present in the atmosphere in greater amounts than at
any time in at least 220,000 years. Certainly something is heating
the globe. The century's 10 warmest years have all occurred since
1983, seven in this decade. A new National Science Foundation
study based on natural indicators such as tree rings, ice-cores
and corals finds the last decade of the millennium has been its
hottest. And 1998 was by far the hottest year. Temperatures surged
faster than previously documented to break a record set just
in 1997.
Middle
and lower latitude mountain glaciers are showing the effects.
University of Colorado glaciologists at Boulder in 1998 reported
that those glaciers have retreated on average at least 60 feet
since 1961, and the rate at which they are melting is increasing.
The retreat of mountain ice in tropical and subtropical latitudes
provides "some of the most compelling evidence yet for recent
global warming," Ohio State University researchers note.
A new
study by NASA's Goddard Institute found Greenland glaciers appear
to be spewing icebergs into the ocean faster than in the past.
The finding was unexpected, and raises fears that global sea
levels, already projected to rise 20 inches next century, could
increase even faster.
Predictions
that global warming will be greatest in the polar regions are
now being borne out. Arctic sea ice has been shrinking by 3 percent
each decade since 1970. Several of the years with the smallest
sea ice coverage were in the 1990s. Around the Antarctic Peninsula,
extensive sea ice formed 4 winters out of every 5 in the mid-century.
Since the 1970s that dropped to 1-2 winters out of 5.
Several
Peninsula ice shelves, which attach to the continent but stretch
into the sea, are in retreat. Some of the most dramatic losses
came in 1998, when around 2,000 square miles calved into icebergs.
The loss in one year equaled the average of 10-15. The Larsen
A ice shelf, after years of slowly melting away, suddenly disintegrated
in 1995. Scientists have now mounted a death watch for Larsen
B and Wilkens, together three times larger than Delaware.
Since
ice shelves already displace water, the loss will not add to
rising ocean levels. But melting northern tundra could have a
devastating global effect. Carbon in tundra soils, equal to one-third
that in the atmosphere, could be released.
Tundra
researcher George W. Kling of the University of Michigan says,
"Our latest data show that the Arctic is no longer a strong
sink for carbon. In some years, the tundra is adding as much
or more carbon to the atmosphere than it removes."
A warmer
atmosphere is expected to cause more evaporation, making for
worse droughts and more deluges. Beginning around 1980, sections
of the U.S., Europe, Africa and Asia did begin to experience
more dry spells, while parts of the U.S. and Europe have become
much wetter.
The
National Climatic Data Center scrutinized U.S. weather records
for extremes expected to increase under global warming. NCDC
discovered that wild weather has been surging since the late
1970s. Statistical analysis showed only 1-in-20 odds that was
a natural fluctuation. NCDC Chief Scientist Tom Karl commented,
"I would say the climate is responding to greenhouse gases."
Thick,
precipitation-prone clouds significantly increased over Australia,
Europe and the United States between 1951 and 1981. Researchers
concluded the increase is "likely to be related" to
human-caused greenhouse gases.
Cloud
cover holds in heat after the sun goes down. So nighttime warming
is a significant global warming indicator. Nighttime temperatures
are going up more than twice as fast as daytime temperatures.
Extreme summer heat waves in the U.S increased 88 percent between
1949-95, with the biggest heat increases coming at night.
Warming
is having devastating impacts on plants and animals. Coral reefs,
the "rainforests of the ocean" where one-quarter of
all marine species are found, suffered record die-offs due to
heat-induced bleaching in 1998.
"At
this time, it appears that only global warming could have induced
such extensive bleaching simultaneously throughout the disparate
reef regions of the world," a State Department scientific
report concluded.
A dramatic
temperature increase off North America's west coast began around
1977. Zooplankton, the microscopic plant-eaters that form the
base of the marine food chain, dropped 70 percent because warmer
waters suppressed colder, nutrient-rich currents. Indicating
food chain collapse, ocean seabirds in the California Current
have declined 90 percent since 1987.
As the
Pacific has warmed, so has Alaska. On the south central coast,
cool temperatures normally keep the spruce bark beetle under
control. But with the warming the beetles have killed most trees
over three million acres, one of the largest insect-caused forest
deaths in North American history.
Evidence
is mounting that global warming is here and humanity is driving
it. Remaining scientific uncertainty "does not justify inaction
in the mitigation of human-induced climate change and/or the
adaptation to it," the American Geophysical Union said in
a recent statement.
The
emerging scientific consensus leaves us with no excuses. We must
rapidly transition from fossil fuels to clean energy. The global
climate crisis, perhaps the greatest challenge in the history
of civilization, calls upon us to act decisively and without
delay. 
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