AAAS: Climate experts urge immediate action to offset impact of global warming
- Complete text... see link to powerpoint presentations (pdf).
16 June 2004
American Association for the Advancement of Science (AAAS)
Climate experts urge immediate action to offset impact of global
Governments and consumers in the United States and worldwide should
take immediate steps to reduce the threat of global warming and to
prepare for a future in which coastal flooding, reduced crop yields
and elevated rates of climate-related illness are all but certain,
top U.S. scientists said Tuesday.
At a meeting organized by AAAS and its journal, Science, the climate
researchers argued that while some policy experts and sectors of the
public dispute the risk, there is in fact no cause for doubt: The
world is significantly warmer today than it was a century ago--and
it's getting warmer. Without action now, they warned, the impact
could be devastating.
As the Earth warms, ice sheets are melting and sea levels are rising--
island and river-delta communities already are vanishing beneath the
waves. Native Inuit fishermen are falling through thinning Arctic ice
they've traversed many times before. In recent decades, climate
change claimed some 150,000 lives in 2000 and sickened many others,
especially elderly people and very young children, according to the
World Health Organization.
One of the conference experts, Harvard geochemistry Professor Daniel
Schrag, likened the situation to the Titanic after it hit the
iceberg. "So if you're standing at the back of the Titanic, you're
thinking, 'Oh, I'm going up, we can't be sinking'."
"We are performing an experiment at a planetary scale that hasn't
been done for millions of years," Schrag said. "This should not be a
partisan issue," he added. "We cannot wait for a catastrophe to
appear before we act because by then it would be too late. The next
few decades will determine our path for the next century."
Another panelist examined what is known about the interaction between
the atmosphere, sea ice and the ocean in the North Atlantic from
studies using observations, data and modeling. "The next 100 years
will experience climate changes on a much greater scale than we've
seen over the past 150 years," said David Battisti, professor of
atmospheric sciences at the University of Washington. "We can
reliably say that the planet will be much warmer."
Schrag and Battisti were part of an all-star panel of climate experts
convened Tuesday 15 June by AAAS, the world's largest general science
society, and its journal, Science. They and other influential
researchers, including Nobel Laureate in Chemistry Sherwood Rowland
of the University of California-Irvine, shared their latest findings
and best temperature projections at the free, public conference. The
forum--"Qs and AAAs About Global Climate Change"--was organized by
Science Editor-in-Chief Donald Kennedy and Albert Teich, director of
Science & Policy for AAAS.
In this way, the U.S. researchers took some first steps toward
responding to a 9 January Science article by Sir David King, the
United Kingdom's chief scientific adviser, which challenged America
to better control greenhouse gases. (Reference:
Many experts at the conference suggested that the onus is on the U.S.-
-and the American public--to makes changes that will reduce the
nation's disproportionate impact on the world environment. "You hope
that somehow people will understand that we have got to do something
now," Joyce Penner, an atmospheric scientist at the University of
Michigan, told Reuters in an interview. "Some people get it -- some
people are driving hybrids. But there is a problem with the American
Kennedy was among those to predict that climate change could bring
potentially disastrous repercussions in communities around the world.
"It should go without saying that the vulnerability of the world's
poor will be multiplied many-fold if global warming causes
significant melting of one or both of the polar ice sheets," Kennedy
said in an interview before the conference. "Yet exacerbation of
poverty around the world--whether from flooding, reduced crop yields
or increased prevalence of asthma, diarrhea, malaria or other
illnesses--is part of the climate-change story that hasn't really
been told. That is why it's important to make the science underlying
climate change accessible to policymakers in parts of the world, like
the United States, where much of the source of the problem lies."
Michael Oppenheimer, professor of geosciences and international
affairs at Princeton University, agreed.
"By mid-century, millions more poor children around the world are
likely to face displacement, malnourishment, disease and even
starvation unless all countries take action now to slow global
warming," he said in an interview.
"Mansions along the Hamptons of Long Island, New York, can be rebuilt
further inland when the beaches erode. But imagine the difficulties
faced by families in Bangladesh. An area where about 8 million people
now live would be underwater if global sea level were to rise half a
meter. Where are they going to go?"
The authoritative Intergovernmental Panel on Climate Change (IPCC),
established by the World Meteorological Organization and the United
Nations Environment Programme, has estimated that, between 1900 and
2100, temperatures will rise between 1.4 and 5.8 degrees Celsius (2.5
to 10.4 F). In the past century, the IPCC has reported, temperatures
have increased between 0.2 and 0.6 degrees C-or, an increase of about
1 degree F to date, with most of the warming happening over the most
Scientists generally agree that temperatures are rising as a result
of human activities such as fossil-fuel burning, which releases
carbon dioxide and other heat-trapping greenhouse gases. This warming
has caused glacial melting and subsequent increases in sea levels
worldwide of up to 20 centimeters, or 7.8 inches.
Some scientists have disputed the pessimistic climate-change
forecasts, and the administration of U.S. President George W. Bush
has cited concerns about the models that predict dramatic climate
change and the perilous consequences. White House science adviser
John H. Marburger III earlier this year defended Bush's policy and
rejected critics' claims that the administration is in denial about
global warming. For example, he said, Bush acknowledged in 2001 that
the concentration "of greenhouse gases, especially CO2, have
increased substantially since the beginning of the Industrial
Rowland, in his remarks at the AAAS conference, said it's not just
carbon dioxide concentrations that are rising. The levels of other
greenhouse gases--water vapor, methane, nitrous oxide and ozone--are
rising too, he said.
Water vapor is not produced by human activities in significant enough
amounts to worry about, Rowland said. Even so, he noted, if human-
related activity changes the temperature of the ocean, then water
Methane concentrations increased from 300 parts per million in 1958
to 380 ppm in April 2004, he said. Carbon dioxide concentrations were
280 ppm in 1800 and 380 ppm in 1980. Concentrations of nitrous oxide
and tropospheric ozone are going up as well.
A century ago, Rowland said, only a handful of cities worldwide
claimed a population of over 1 million. Today, there are more than 50
cities with multi-million populations. "Having large cities, and many
motorized cities today, is an important reason why tropospheric ozone
is on the rise," he said.
The scientists at Tuesday's climate conference acknowledged that
questions remain about climate-forecasting models. And, they said,
there will always be uncertainty about exactly what may happen and
precisely how various factors exert an influence. However, the
panelists also agreed that accurate predictions can be made over the
long term--and that greenhouse gases released as a result of human
activity are a major change agent. In fact, they said, the models are
more likely making conservative predictions rather than generous
"We have seen a huge increase in the capabilities of these models,"
said Gerald A. Meehl, a research scientist at the National Center for
Atmospheric Research. "They do quite well in simulating global
temperature evolution and extremes."
According to Oppenheimer, models project that if Greenland
temperatures rise by another 3 degrees C, complete melting of the
Greenland ice sheet would eventually result. "If the West Antarctic
ice sheet becomes unstable, global sea level would rise about 5
meters and as much as seven meters if the Greenland ice sheet melts,"
Oppenheimer said. Although the sea level rise would largely occur in
later centuries, these outcomes could be set in place within the
"Antarctica is very dramatically losing ice at this point,"
Oppenheimer told reporters at the conference. "If Greenland or West
Antarctica disintegrated, the state of Florida would disappear."
Such an outcome isn't imminent, he acknowledged. But would melting
polar ice destabilize ocean circulation, pushing the relatively warm
Gulf Stream southward and causing the North Atlantic to freeze as
depicted in Hollywood's latest disaster movie, "The Day After
Probably not, said Battisti. "One hundred years from now, the amount
of carbon dioxide in the atmosphere is likely to be at least two
times greater than today," he said. "Any localized cooling that might
occur in the North Atlantic will be overwhelmed by a very large
warming caused by a large increase in the greenhouse effect."
Greenhouse gases are warming the Earth faster than aerosols like dust
can mask them, said Penner, professor of atmospheric, oceanic and
space sciences at the University of Michigan. Various types of
aerosols--from soot and dust to sulfur--can either cool or warm the
climate, she explained. Warming is associated with absorbing black
carbon emissions such as soot, while non-absorbing aerosols are tied
to cooling, which scientists call "negative forcing."
"Greenhouse gas effects are not going to be masked by aerosols,"
Penner said in an interview, debunking a popular myth related to
climate change. "Even the best current aerosol models overestimate
the cooling force of aerosols. Warming caused by greenhouse gases
will overwhelm any aerosol-related cooling."
At the conference, Penner said many questions remain about
aerosols. "In spite of this uncertainty," she said, "there is going
to be a major change in the future. Once we're into this future,
we're into it for a long time."
Alan I. Leshner, AAAS CEO and executive publisher of Science, joined
Kennedy in co-hosting the conference, which was sponsored by the
William and Flora Hewlett Foundation and the Conference Board. Among
the other speakers were Thomas Crowley, Duke University; Richard
Alley, Pennsylvania State University; Lonnie Thompson, Ohio State
University; and Chris Field, Carnegie Institution of Washington.
Ginger Pinholster, Barbara Rice and Monica Amarelo
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