Experts cite 'strong evidence' of global warming
Panel finds spike in temperatures over last two decades
January 13, 2000
Web posted at: 11:41 a.m. EST (1641 GMT)
WASHINGTON (CNN) -- A blue-ribbon panel of climate
scientists has issued a report saying that global warming is "undoubtedly real."
CNN's Rick Lockridge explains the study.
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The report, announced Wednesday night in a statement
by the National Academy of Science's National Research
Council, takes an unusually strong stand on the issue. It also undermines a principal argument used by
scientists who dissent with the majority view, which is that
global warming is well under way with possibly dire environmental consequences.
The panel stopped short of declaring a definite link
between human activity and global warming.
Temperature has risen sharply
Global temperatures have risen more sharply in the past 20 years than at any time this century, according to the panel, led by John Wallace of the University of
The panel of scientists says that contradictory evidence from
satellite data, used by some scientists and
political activists to dismiss reports of a warming
planet, is irrelevant.
NASA scientist John Christy, compiling satellite data
extending back to 1979, has contended that temperature
measurements in the Earth's upper atmosphere show a
cooling of two degrees Fahrenheit over the past two
Because most climate scientists have presumed that
global warming would affect all layers of the
atmosphere in a uniform way, Christy's research
has been a cornerstone argument for those who disagree
with reports on the severity or even the existence of
Differing temperatures don't disprove trend
But two years ago, Christy acknowledged math errors in
his computations that reduced the cooling measurements
to about one-half degree Fahrenheit.
Wednesday's report asserts that external factors,
including the thinning layer of ozone in the Earth's
upper atmosphere; the rapid rise in particulate
pollution from the burning of fossil fuels; and
natural impacts like the massive 1991 eruption of the
Mount Pinatubo volcano in the Philippines make it
possible for the upper atmosphere to cool while the
Earth's surface is rising to record temperatures.
"The differences between the surface and upper-air
trends in no way invalidates the conclusion that the
Earth's temperature is rising," said Wallace, the
Christy is one of 11 scientists who participated
in the panel that produced the new report.
The most comprehensive assessment to date of the
possible impacts of global warming are contained in
the 1995 report of the Intergovernmental Panel on Climate Change, or IPCC, a United Nations-sponsored
effort of more than 2,500 climate scientists, including the
'Blanket' wrapping Earth's surface
The IPCC reached a near-unanimous conclusion that
global warming was at least partially a result of
human activity -- primarily the burning of fossil
fuels, which release carbon dioxide, methane, and
other gases into the atmosphere, forming a global
"blanket" that traps heat near the Earth's surface.
The IPCC predicted an increase in global temperatures
of between 2 and 6.3 degrees Fahrenheit by the year
2100. The panel also predicted the expansion of
warming oceans, and the melting of land-based ice
formations would combine to add between one and three
feet to sea level.
The IPCC projected increases in the frequency and
intensity of storms and droughts; spread of tropical
diseases; sharp increases in coastal flooding; and an
accelerated wave of extinctions of plant and animal
species which fail to adapt to the changing climate.
Wednesday's panel also included Benjamin Santer, a
principal author of the IPCC report; and James Hansen,
whose dramatic 1988 testimony before the U.S. Congress
triggered some of the first widespread reports of
The topic of global warming has spawned parallel
debates in the scientific and the political
China to lead U.S. in greenhouse emissions
A 1997 global conference in Kyoto, Japan resulted in a
treaty that would commit industrialized nations to
reductions in so-called greenhouse gas emissions; but
the U.S. Senate has remained staunchly opposed to
ratifying the treaty -- nullifying its impact in the
nation that currently leads the world in Greenhouse
Critics of the treaty say the economies of
industrialized nations would suffer under the Kyoto
Accords, which would impose no such limits on
developing nations at this time.
China, with a booming, coal-based economy, is
projected to zoom past the United States in greenhouse
emissions by 2025.
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