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Carbon output must near zero

Page history last edited by PBworks 16 years ago
Carbon Output Must Near Zero To Avert Danger, New Studies Say
By Juliet Eilperin
Washington Post Staff Writer
Monday, March 10, 2008; A01

The task of cutting greenhouse gas emissions enough to avert a
dangerous rise in global temperatures may be far more difficult
than previous research suggested, say scientists who have just
published studies indicating that it would require the world to
cease carbon emissions altogether within a matter of decades.

Their findings, published in separate journals over the past few
weeks, suggest that both industrialized and developing nations
must wean themselves off fossil fuels by as early as mid-century
in order to prevent warming that could change precipitation
patterns and dry up sources of water worldwide.

Using advanced computer models to factor in deep-sea warming and
other aspects of the carbon cycle that naturally creates and
removes carbon dioxide (CO2), the scientists, from countries
including the United States, Canada and Germany, are delivering a
simple message: The world must bring carbon emissions down to near
zero to keep temperatures from rising further.

"The question is, what if we don't want the Earth to warm
anymore?" asked Carnegie Institution senior scientist Ken
Caldeira, co-author of a paper published last week in the journal
Geophysical Research Letters. "The answer implies a much more
radical change to our energy system than people are thinking
about."

Although many nations have been pledging steps to curb emissions
for nearly a decade, the world's output of carbon from human
activities totals about 10 billion tons a year and has been
steadily rising.

For now, at least, a goal of zero emissions appears well beyond
the reach of politicians here and abroad. U.S. leaders are just
beginning to grapple with setting any mandatory limit on
greenhouse gases. The Senate is poised to vote in June on
legislation that would reduce U.S. emissions by 70 percent by
2050; the two Democratic senators running for president, Hillary
Rodham Clinton (N.Y.) and Barack Obama (Ill.), back an 80 percent
cut. The Republican presidential nominee, Sen. John McCain
(Ariz.), supports a 60 percent reduction by mid-century.

Sen. Barbara Boxer (D-Calif.), who is shepherding climate
legislation through the Senate as chairman of the Environment and
Public Works Committee, said the new findings "make it clear we
must act now to address global warming."

"It won't be easy, given the makeup of the Senate, but the science
is compelling," she said. "It is hard for me to see how my
colleagues can duck this issue and live with themselves."

James L. Connaughton, who chairs the White House Council on
Environmental Quality, offered a more guarded reaction, saying the
idea that "ultimately you need to get to net-zero emissions" is
"something we've heard before." When it comes to tackling such a
daunting environmental and technological problem, he added: "We've
done this kind of thing before. We will do it again. It will just
take a sufficient amount of time."

Until now, scientists and policymakers have generally described
the problem in terms of halting the buildup of carbon in the
atmosphere. The United Nations' Framework Convention on Climate
Change framed the question that way two decades ago, and many
experts talk of limiting CO2concentrations to 450 parts per
million (ppm).

But Caldeira and Oregon State University professor Andreas
Schmittner now argue that it makes more sense to focus on a
temperature threshold as a better marker of when the planet will
experience severe climate disruptions. The Earth has already
warmed by 0.76 degrees Celsius (nearly 1.4 degrees Fahrenheit)
above pre-industrial levels. Most scientists warn that a
temperature rise of 2 degrees Celsius (3.6 degrees Fahrenheit)
could have serious consequences.

Schmittner, lead author of a Feb. 14 article in the journal Global
Biogeochemical Cycles, said his modeling indicates that if global
emissions continue on a "business as usual" path for the rest of
the century, the Earth will warm by 7.2 degrees Fahrenheit by
2100. If emissions do not drop to zero until 2300, he calculated,
the temperature rise at that point would be more than 15 degrees
Fahrenheit.

"This is tremendous," Schmittner said. "I was struck by the fact
that the warming continues much longer even after emissions have
declined. . . . Our actions right now will have consequences for
many, many generations. Not just for a hundred years, but
thousands of years."

While natural cycles remove roughly half of human-emitted carbon
dioxide from the atmosphere within a hundred years, a significant
portion persists for thousands of years. Some of this carbon
triggers deep-sea warming, which keeps raising the global average
temperature even after emissions halt.

Researchers have predicted for a long time that warming will
persist even after the world's carbon emissions start to fall and
that countries will have to dramatically curb their carbon output
in order to avert severe climate change. Last year's report of the
U.N. Intergovernmental Panel on Climate Change said industrialized
nations would have to cut emissions 80 to 95 percent by 2050 to
limit CO2concentrations to the 450 ppm goal, and the world as a
whole would have to reduce emissions by 50 to 80 percent.

European Union Environment Commissioner Stavros Dimas, in
Washington last week for meetings with administration officials,
said he and his colleagues are operating on the assumption that
developed nations must cut emissions 60 to 80 percent by
mid-century, with an overall global reduction of 50 percent. "If
that is not enough, common sense is that we would not let the
planet be destroyed," he said.

The two new studies outline the challenge in greater detail, and
on a longer time scale, than many earlier studies. Schmittner's
study, for example, projects how the Earth will warm for the next
2,000 years.

But some climate researchers who back major greenhouse gas
reductions said it is unrealistic to expect policymakers to think
in terms of such vast time scales.

"People aren't reducing emissions at all, let alone debating
whether 88 percent or 99 percent is sufficient," said Gavin
A. Schmidt, of NASA's Goddard Institute for Space Studies. "It's
like you're starting off on a road trip from New York to
California, and before you even start, you're arguing about where
you're going to park at the end."

Brian O'Neill of the National Center for Atmospheric Research
emphasized that some uncertainties surround the strength of the
natural carbon cycle and the dynamics of ocean warming, which in
turn would affect the accuracy of Caldeira's modeling. "Neither of
these are known precisely," he said.

Although computer models used by scientists to project changes in
the climate have become increasingly powerful, scientists
acknowledge that no model is a perfect reflection of the complex
dynamics involved and how they will evolve with time.

Still, O'Neill said the modeling "helps clarify thinking about
long-term policy goals. If we want to reduce warming to a certain
level, there's a fixed amount of carbon we can put into the
atmosphere. After that, we can't emit any more, at all."

Caldeira and his colleague, H. Damon Matthews, a geography
professor at Concordia University in Montreal, emphasized this
point in their paper, concluding that "each unit of CO2emissions
must be viewed as leading to quantifiable and essentially
permanent climate change on centennial timescales."

Steve Gardiner, a philosophy professor at the University of
Washington who studies climate change, said the studies highlight
that the argument over global warming "is a classic
inter-generational debate, where the short-term benefits of
emitting carbon accrue mainly to us and where the dangers of them
are largely put off until future generations."

When it comes to deciding how drastically to reduce greenhouse gas
emissions, O'Neill said, "in the end, this is a value judgment,
it's not a scientific question." The idea of shifting to a
carbon-free society, he added, "appears to be technically
feasible. The question is whether it's politically feasible or
economically feasible."

 

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