FYI, today (Feb. 2) is also the anniversary of the signing of the Treaty of Guadalupe Hidalgo. That somehow seems significant.
Panel Issues Bleak Report on Climate Change
By ELISABETH ROSENTHAL and ANDREW C. REVKIN
Published: February 2, 2007
PARIS, Feb. 2 In a bleak and powerful assessment of the future of
the planet, the leading international network of climate change
scientists has concluded for the first time that global warming is
"unequivocal" and that human activity is the main driver, "very
likely" causing most of the rise in temperatures since 1950.
In its fourth assessment of global warming, released Friday, the
Intergovernmental Panel on Climate Change used its strongest language
yet in drawing a link between human activity and recent warming.
They said the world is already committed to centuries of warming,
shifting weather patterns and rising seas, resulting from the buildup
of gases in the atmosphere that trap heat. But the warming can be
substantially blunted by prompt action, the panel of scientists said
in a report released here today.
The report summarized the fourth assessment since 1990 by the group,
the Intergovernmental Panel on Climate Change of the United Nations,
sizing up the causes and consequences of climate change. But it is the
first in which the group asserts with near certainty more than 90
percent confidence that carbon dioxide and other heat-trapping
greenhouse gases from human activities have been the main causes of
warming since 1950.
In its last report, in 2001, the panel, consisting of hundreds of
scientists and reviewers, put the confidence level at between 66 and
90 percent. Both reports are online at http://www.ipcc.ch
If carbon dioxide concentrations in the atmosphere reach twice their
pre-industrial levels, the report said, the global climate will
probably warm by 3.5 to 8 degrees. But there would be more than a
1-in-10 chance of much greater warming, a situation many earth
scientists say poses an unacceptable risk.
Many energy and environment experts see such a doubling as a foregone
conclusion sometime after midcentury unless there is a prompt and
sustained shift away from the 20th-century pattern of unfettered
burning of coal and oil, the main sources of carbon dioxide, and an
aggressive quest for expanded and improved nonpolluting energy options.
Even an increased level of warming that falls in the middle of the
group’s range of projections would likely cause significant stress to
ecosystems and alter longstanding climate patterns that shape water
supplies and agricultural production, according to many climate
experts and biologists.
While the new report projected a modest rise in seas by 2100 between
7 and 23 inches it also concluded that seas would continue to rise,
and crowded coasts retreat, for at least 1,000 years to come. By
comparison, seas rose about 6 to 9 inches in the 20th century.
John P. Holdren, an energy and climate expert at Harvard University,
said that the “report powerfully underscores the need for a massive
effort to slow the pace of global climatic disruption before
intolerable consequences become inevitable.” [Read a report by Mr.
Holdren. (PDF format)]
“Since 2001 there has been a torrent of new scientific evidence on the
magnitude, human origins and growing impacts of the climatic changes
that are underway,” said Mr. Holdren, who is the president of the
American Association for the Advancement of Science. “In overwhelming
proportions, this evidence has been in the direction of showing faster
change, more danger and greater confidence about the dominant role of
fossil fuel burning and tropical deforestation in causing the changes
that are being observed.”
The conclusions came after a three-year review of hundreds of studies
of clues illuminating past climate shifts, observations of retreating
ice, warming and rising seas, and other shifts around the planet, and
a greatly expanded suite of supercomputer simulations used to test how
earth will respond to a building blanket of gases that hold heat in
The section released today was a 20-page summary for policymakers,
which was approved early this morning by teams of officials from more
than 100 countries after three days and nights of wrangling over
wording with the lead authors, all of whom are scientists.
It described far-flung ramifications for both humans and nature.
“It is very likely that hot extremes, heat waves and heavy
precipitation events will continue to become more frequent,” said the summary.
Generally, the scientists said, more precipitation will fall at higher
latitudes, which are likely also to see lengthened growing seasons,
while semi-arid, subtropical regions already chronically beset by
drought could see a further 20-percent drop in rainfall under the
midrange scenario for increases in the greenhouse gases.
The summary added a new chemical consequence of the buildup of carbon
dioxide to the list of mainly climatic and biological impacts foreseen
in its previous reports: a drop in the pH of seawater as oceans absorb
billions of tons of carbon dioxide, which forms carbonic acid when
partly dissolved. Marine biologists have said that could imperil some
kinds of corals and plankton.
A vast improvement in the science of climatology including “larges
amounts of new and more comprehensive data” has allowed the group to
become far more confident and specific in its predictions, compared
with its previous assessment in 2001, the authors said.
The report essentially caps a half-century-long effort to discern
whether humans, through the buildup of carbon dioxide and other gases
released mainly by burning fuels and forests, could influence the
earth’s climate system in potentially momentous ways.
The group operates under the aegis of the United Nations and was
chartered in 1988 a year of record heat, burning forests, and the
first big headlines about global warming to provide regular reviews
of climate science to governments to inform policy choices.
Government officials are involved in shaping the summary of each
report, but the scientist-authors, who are unpaid, have the final say
over the thousands of pages in four underlying technical reports that
will be completed and published later this year.
Big questions remain about the speed and extent of some impending
changes, both because of uncertainty about future population and
pollution trends and the complex interrelationships of the greenhouse
emissions, clouds, dusty kinds of pollution, the oceans and earth’s
veneer of life, which both emits and soaks up carbon dioxide and other
But a broad array of scientists, including authors of the report and
independent experts, said the latest analysis was the most sobering
view yet of a century of transition after thousands of years of
relatively stable climate conditions to a new norm of continual change.
Should greenhouse gases continue to accumulate in the atmosphere at
even a moderate pace, average temperatures by the end of the century
could match those last seen 125,000 years ago, in the previous warm
spell between ice ages, the report said.
At that time, the panel said, sea levels were 12 to 20 feet higher
than they are now. Muych of that extra water is now trapped in the ice
sheets of Greenland and Antarctica, which are eroding in some places.
The panel said there was no solid scientific understanding of how
rapidly the vast stores of ice in polar regions will melt, so their
estimates on new sea levels were based mainly on how much the warmed
oceans will expand, and not on contributions from the melting of ice
now on land.
Other scientists have recently reported evidence that the glaciers and
ice sheets in the Arctic and Antarctic could flow seaward far more
quickly than estimated in the past, and they have proposed that the
risks to coastal areas could be much more imminent. But the I.P.C.C.
is proscribed by its charter from entering into speculation, and so
could not include such possible instabilities in its assessment.
Michel Jarraud, the secretary general of the United Nations World
Meteorological Organization, said the lack of clarity should offer no
one comfort. “The speed with which melting ice sheets are raising sea
levels is uncertain, but the report makes clear that sea levels will
rise inexorably over the coming centuries,” he said. “It is a question
of when and how much, and not if,” he said, adding: “While the
conclusions are disturbing, decision makers are now armed with the
latest facts and will be better able to respond to these realities.”
Achim Steiner, the executive director of the United Nations
Environment Program, which oversees the I.P.C.C. along with the
meteorological group, said society now had plenty of information on
which to act.
“The implications of global warming over the coming decades for our
industrial economy, water supplies, agriculture, biological diversity
and even geopolitics are massive,” he said. “This new report should
spur policymakers to get off the fence and put strong and effective
policies in place to tackle greenhouse gas emissions.”
The warming and other climate shifts will be highly variable around
the world, with the Arctic particularly seeing much higher
temperatures, said Susan Solomon, the co-leader of the team writing
the summary and the section of the I.P.C.C. report on basic science.
She is an atmospheric scientist for the National Oceanic and
The kinds of vulnerabilities are very much dependent on where you are,
Dr. Solomon said in a telephone interview. “If you’re living in parts
of tropics and they’re getting drier and you’re a farmer there are
some very acute issues associated with even small changes in rainfall
changes we’re already seeing are significant,” she said. “If you are
an Inuit and you’re seeing your sea ice retreating already that’s
affecting your lifestyle and culture.”
The 20-page summary is a sketch of the findings that are most germane
to the public and world leaders.
The full I.P.C.C. report, thousands of pages of technical background,
will be released in four sections through the year the first on
basic science, then sections on impacts and options for limiting
emissions and limiting inevitable harms, and finally a synthesis of
all of the findings near year’s end.
In a news conference in Paris, Dr. Solomon declined to provide her own
views on how society should respond to the momentous changes projected
in the study.
“I honestly believe that it would be a much better service for me to
keep my personal opinions separate than what I can actually offer the
world as a scientist,” she said. “My stepson, who is 29, has an
utterly different view of risks than I do. People are going to have to
make their own judgments.”
Some authors of the report said that no one could honestly point to
any remaining uncertainties as justification for further delay.
“Policy makers paid us to do good science, and now we have high very
scientific confidence in this work this is real, this is real, this
is real,” said Richard B. Alley, one of the lead authors and a
professor at Penn State University. “So now act, the ball’s back in
Elisabeth Rosenthal reported from Paris, and Andrew C. Revkin from New York.
Even Before Its Release, World Climate Report Is Criticized as Too Optimistic
By CORNELIA DEAN
Published: February 2, 2007
In its 2001 assessment, its third, the Intergovernmental Panel on
Climate Change estimated that in the next hundred years sea level
would rise globally by at least a few inches and perhaps as much as
three feet, a catastrophe for low-lying coastal areas and island nations.
In Paris today the panel will issue its fourth assessment, and people
familiar with its deliberations say it will moderate its gloom on sea
level rise, lowering its worst-case estimate.
In theory that is good news, because rising seas bring erosion and
flooding to coastal areas. But a lower estimate has not been uniformly
In letters to and conversations with panel members, and in scientific
journals, several climate experts said the estimate was almost
certainly wrong because the panel was leaving out a growing body of
data on melting glaciers and inland ice sheets, which are major
contributors to sea level rise.
Those experts say that unless the finding is modified, the panel
widely cited as an authoritative voice on climate change risks
condemning itself to irrelevance.
Climate experts have “a great deal of confidence” in observations that
sea level rise is accelerating, said Laury Miller, an oceanographer at
the National Oceanographic and Atmospheric Administration who was a
reviewer for part of the coming report.
Good satellite measurements date only from the last decade or so, he
said, so it is hard to draw firm long-term conclusions from them.
Also, he said, computer models of how glaciers and ice sheets melt
cannot account for much of the observed melting, even though
“presumably it is going into the ocean.”
But so far at least, he said, “the observed sea level rise has been
tracking the upper range” of the 2001 estimate. “It’s pretty
unequivocal,” he said.
Michael C. MacCracken, who led the Office of Climate Change in the
Clinton administration and who was also a reviewer for some of the new
assessment, said he could understand why scientists on the panel might
be uneasy about relying too much on models. But in that event, he
said, they should make it known that their estimates did not include
factors like ice sheet movement and collapse, which appear to be accelerating.
In a letter to panel members on Jan. 21, Dr. MacCracken said lowering
the worst-case sea level estimate would “result in a serious
misimpression being conveyed to policy makers and the public.” In
fact, he said, most American experts have felt that the estimate was
already too optimistic.
Other experts said the panel might have missed some important new
developments, because it set a December 2005 cutoff date for
submission of scientific papers and other data.
Since then, researchers have reported that Greenland’s ice sheet is
melting faster than had been thought, that Antarctica is feeding more
melt water into the oceans than had been predicted and that the
melting of glaciers around the world is accelerating rapidly.
In a brief report in today’s issue of the journal Science, an array of
leading climate researchers said recent findings “raise concern that
the climate system, in particular sea level, may be responding
more quickly than climate models indicate.”
But in an interview last week, Susan Solomon, a climate expert at the
National Oceanographic and Atmospheric Administration and a leader of
one of the climate panel’s working groups, said researchers were
invited several times last year to comment on the group’s work. It
received thousands of comments, she said.
Drew Shindell, a climate expert at the NASA Goddard Institute for
Space Studies, said at a House of Representatives hearing on climate
science on Tuesday that part of the problem was the difficulty of
making firm scientific statements about a field in which research was
Dr. Shindell, who emphasized that he was speaking as an individual,
said, “The melting of Greenland has been accelerating so incredibly
rapidly that the I.P.C.C. report will already be out of date in
predicting sea level rise, which will probably be much worse than is
predicted in the I.P.C.C. report.”
James McCarthy, a climate expert at Harvard who was a leader in the
2001 assessment, noted in an e-mail message that the panel’s report
could be changed until the moment it was made public. Nevertheless, he
said he worried that unless its discussion of sea level rise was
altered, the panel would so underestimate the problem that it would
look “foolishly cautious and maybe even irrelevant” on the issue.
But one prominent critic of mainstream climate science, S. Fred
Singer, a retired physicist, is already seizing on the report as
evidence that people like former Vice President Al Gore who argue that
human activity is changing the earth’s climate are now the contrarians.
Andrew C. Revkin contributed reporting.