Global Warming: Scientific Evidence
By PATRICK MAZZA and RHYS ROTH
A 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% 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 four
winters out of every five in the mid-century. Since the 1970s that dropped
to 1-2 winters out of five.
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
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
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% 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-off due to heat-induced bleaching
"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% because warmer waters suppressed colder,
nutrient-rich currents. Indicating food chain collapse, ocean seabirds in
the California Current have declined 90% 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. A rapid shift from fossil fuels
is utterly crucial. Writing recently in Nature, 11 scientists said
bringing on clean energy sources rapidly enough to stabilize the climate
"could require efforts, perhaps international, pursued with the urgency
of the Manhattan Project or the Apollo space program ... the potentially
adverse effect of humanity on the Earth's climate could well stimulate new
industries in the 21st century, as did the Second World War and the 'cold
war' of this century."
This article is excerpted from a new white paper, "Global Warming
Is Here: The Scientific Evidence," available from Climate Solutions,
610 E. 4th St., Olympia, WA 98501; phone 360-352-1763, email@example.com
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