Science Panel Says Global Warming Is ‘Unequivocal’
Source: Copyright 2007, New York Times
Date: February 3, 2007
Byline: Elisabeth Rosenthal and Andrew C. Revkin


Dan Crosbie/Canadian Ice Service
Polar bears on chunks of glacial ice in the Bering Sea in 2004. Much higher temperatures are forecast for the Arctic, climate scientists say.


Reuters
A worker at an industrial-residue disposal site in Hanshou County in central China Friday. A climate panel has concluded that human industrial activity is “very likely” driving global temperature rises.



In a grim and powerful assessment of the future of the planet, the leading international network of climate 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.

They said the world was in for centuries of climbing temperatures, rising seas and shifting weather patterns — unavoidable results of the buildup of heat-trapping gases in the atmosphere.

But their report, released here on Friday by the Intergovernmental Panel on Climate Change, said warming and its harmful consequences could be substantially blunted by prompt action.

While the report provided scant new evidence of a climate apocalypse now, and while it expressly avoided recommending courses of action, officials from the United Nations agencies that created the panel in 1988 said it spoke of the urgent need to limit looming and momentous risks.

“In our daily lives we all respond urgently to dangers that are much less likely than climate change to affect the future of our children,” said Achim Steiner, executive director of the United Nations Environment Program, which administers the panel along with the World Meteorological Organization.

“Feb. 2 will be remembered as the date when uncertainty was removed as to whether humans had anything to do with climate change on this planet,” he went on. “The evidence is on the table.”

The report is the panel’s fourth assessment since 1990 on 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 greenhouse gases from human activities have been the main causes of warming in the past half century.

In its last report, in 2001, the panel, consisting of hundreds of scientists and reviewers, said the confidence level for its projections was “likely,” or 66 to 90 percent. That level has now been raised to “very likely,” better than 90 percent. Both reports are online at www.ipcc.ch.

The Bush administration, which until recently avoided directly accepting that humans were warming the planet in potentially harmful ways, embraced the findings, which had been approved by representatives from the United States and 112 other countries on Thursday night.

Administration officials asserted Friday that the United States had played a leading role in studying and combating climate change, in part by an investment of an average of almost $5 billion a year for the past six years in research and tax incentives for new technologies.

At the same time, Secretary of Energy Samuel Bodman rejected the idea of unilateral limits on emissions. “We are a small contributor to the overall, when you look at the rest of the world, so it’s really got to be a global solution,” he said.

The United States, with about 5 percent of the world’s population, contributes about a quarter of greenhouse gas emissions, more than any other country.

Democratic lawmakers quickly fired off a round of news releases using the report to bolster a fresh flock of proposed bills aimed at cutting emissions of greenhouse gases. Senator James M. Inhofe, the Oklahoma Republican who has called the idea of dangerous human-driven warming a hoax, issued a news release headed “Corruption of Science” that rejected the report as “a political document.”

The new report says the global climate is likely to warm 3.5 to 8 degrees Fahrenheit if carbon dioxide concentrations in the atmosphere reach twice the levels of 1750, before the Industrial Revolution.

Many energy and environment experts see such a doubling, or worse, as a foregone conclusion after 2050 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 expansion of nonpolluting sources of energy.

And the report says there is a more than a 1-in-10 chance of much greater warming, a risk that many experts say is far too high to ignore.

Even a level of warming that falls in the middle of the group’s range of projections would be likely to cause significant stress to ecosystems, according to many climate experts and biologists. And it would alter longstanding climate patterns that shape water supplies and agricultural production.

Moreover, the warming has set in motion a rise in global sea levels, the report says. It forecasts a rise of 7 to 23 inches by 2100 and concludes that seas will continue to rise 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, said the report “powerfully underscores the need for a massive effort to slow the pace of global climatic disruption before intolerable consequences become inevitable.”

“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 under way,” 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 past climate shifts; observations of retreating ice, warming and rising seas, and other changes around the planet; and a greatly expanded suite of supercomputer simulations used to test how the earth will respond to a growing blanket of gases that hold heat in the atmosphere.

The section released Friday was a 20-page summary for policymakers, which was approved early in the 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 also likely to see lengthened growing seasons. Semi-arid subtropical regions, already chronically plagued by drought, could have a further 20 percent drop in rainfall under the panel’s midrange outlook 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 effects 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. The ocean would stay alkaline, but marine biologists have said that a change in the direction of acidity could imperil some kinds of corals and plankton.

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 such gases.

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. Much 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 climate change panel is forbidden by its charter to enter 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.”

The warming and other climate changes will be highly variable around the world, with the Arctic in particular seeing much higher temperatures, said Susan Solomon, the co-leader of the team writing the summary and the section of the panel’s report on basic science. She is an atmospheric scientist for the National Oceanic and Atmospheric Administration.

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 the 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 life style and culture.”

The 20-page summary is a sketch of the findings that are most germane to the public and world leaders.

The full 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 very high 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 Pennsylvania State University. “So now act, the ball’s back in your court.”

Elisabeth Rosenthal reported from Paris, and Andrew C. Revkin from New York. Felicity Barringer contributed reporting from Washington.

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 Friday 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 cheered.

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, 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 Friday'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 moving fast.

Shindell, who emphasized that he was speaking as an individual, said, "The melting of Greenland has been accelerating so incredibly rapidly that the IPCC report will already be out of date in predicting sea level rise, which will probably be much worse than is predicted in the IPCC 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.

World Scientists Near Consensus on Warming
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By JAMES KANTER and ANDREW C. REVKIN
Published: January 30, 2007

PARIS, Jan. 29 — Scientists from across the world gathered Monday to hammer out the final details of an authoritative report on climate change that is expected to project centuries of rising temperatures and sea levels unless there are curbs in emissions of carbon dioxide and other gases that trap heat in the atmosphere.

Scientists involved in writing or reviewing the report say it is nearly certain to conclude that there is at least a 90 percent chance that human-caused emissions are the main factor in warming since 1950. The report is the fourth since 1990 from the Intergovernmental Panel on Climate Change, which is overseen by the United Nations.

The report, several of the authors said, will describe a growing body of evidence that warming is likely to cause a profound transformation of the planet.

Three large sections of the report will be forthcoming during the year. The first will be a summary for policy makers and information on basic climate science, which is expected to be issued on Friday.

Among the findings in recent drafts:

¶The Arctic Ocean could largely be devoid of sea ice during summer later in the century.

¶Europe’s Mediterranean shores could become barely habitable in summers, while the Alps could shift from snowy winter destinations to summer havens from the heat.

¶Growing seasons in temperate regions will expand, while droughts are likely to ravage further the semiarid regions of Africa and southern Asia.

“Concerns about climate change and public awareness on the subject are at an all-time high,” the chairman of the panel, Rajendra Pachauri, told delegates on Monday.

But scientists involved in the effort warned that squabbling among teams and government representatives from more than 100 countries — over how to portray the probable amount of sea-level rise during the 21st century — could distract from the basic finding that a warming world will be one in which shrinking coastlines are the new normal for centuries to come.

Jerry Mahlman, an emeritus researcher at the National Center for Atmospheric Research in Boulder, Colo., who was a reviewer of the report’s single-spaced, 1,644-page summary of climate science, said most of the leaks to the news media so far were from people eager to find elements that were the most frightening or the most reassuring.

He added in an interview that such efforts distracted from the basic, undisputed findings, saying that those point to trends that are very disturbing.

He noted recent disclosures that there is still uncertainty about the pace at which seas will rise because of warming and the melting of terrestrial ice over the next 100 years. That span, he said, is just the start of a rise in sea levels that will almost certainly continue for 1,000 years or so.

Many economists and energy experts long ago abandoned any expectation that it would be possible to avoid a doubling of preindustrial carbon dioxide concentrations, given the growth of human populations, use of fossil fuels, particularly coal, and destruction of forests in the tropics.

The report is likely to highlight the hazardous consequences of that shift by finding that reaching twice the preindustrial concentration of carbon dioxide will probably warm climate between 3.5 and 8 degrees Fahrenheit and by highlighting that there is a small but significant risk that such a buildup can produce even more warming.

One major point of debate in early drafts of the report is the projection of a smaller rise in sea level than the last report as scientists relying on computer models and field observations struggle to find a consensus. Some scientists say that the figures used in the coming report are not recent enough because they leave out recent observations of instability in some ice sheets in Antarctica and Greenland.

Another possible point of contention during the four days of closed sessions in Paris this week may be assertions in early drafts of the report that the recent warming rate was blunted by particle pollution and volcanic eruptions.

Some scientists say the final report should reflect the assumption that the rate of warming in coming years is likely to be more pronounced than that of previous decades.

Achim Steiner, the executive director of the United Nations Environment Program, said the findings presented Friday should lead decision makers to accelerate efforts to slash carbon emissions and to help people in vulnerable parts of the world prepare for climate change.

“These findings should strengthen the resolve of governments to act now to reduce greenhouse gas emissions and put in place the medium- to longer-term strategies necessary to avert dangerous climate change,” Mr. Steiner said.

In a new report issued Monday, his agency said the most recent evidence from mountain glaciers showed that they were melting faster than before.

In the past year, international concern over what to do about global warming has grown along with concrete signs of climate change. Even so, political leaders are still groping for ways to tackle the phenomenon. Europe has adopted a program that caps the amount of emissions from industrial plants.

But the world’s largest emitter, the United States, still is debating whether to adopt a similar policy, while developing countries like China are resisting caps on the ground that the industrialized countries contributed about 75 percent of the current volume of greenhouse gases and should make the deepest cuts.

Many experts involved in the intergovernmental panel’s process said there was hope that with a prompt start on slowing emissions, the chances of seeing much greater warmth and widespread disruption of ecosystems and societies could be reduced.

Outside experts agreed.

“We basically have three choices: mitigation, adaptation and suffering,” said John Holdren, the president of the American Association for the Advancement of Science and an energy and climate expert at Harvard. “We’re going to do some of each. The question is what the mix is going to be. The more mitigation we do, the less adaptation will be required and the less suffering there will be.”

On the Climate Change Beat, Doubt Gives Way to Certainty
Source: Copyright 2007, New York Times
Date: February 6, 2007
Byline: William K. Stevens

In the decade when I was the lead reporter on climate change for this newspaper, nearly every blizzard or cold wave that hit the Northeast would bring the same conversation at work.

Somebody in the newsroom would eye me and say something like, “So much for global warming.” This would often, but not always, be accompanied by teasing or malicious expressions, and depending on my mood the person would get either a joking or snappish or explanatory response. Such an exchange might still happen, but now it seems quaint. It would be out of date in light of a potentially historic sea change that appears to have taken place in the state and the status of the global warming issue since I retired from The New York Times in 2000.

Back then I wrote that one day, if mainstream scientists were right about what was going on with the earth’s climate, it would become so obvious that human activity was responsible for a continuing rise in average global temperature that no other explanation would be plausible.

That day may have arrived.

Similarly, it was said in the 1990s that while the available evidence of a serious human impact on the earth’s climate might be preponderant enough to meet the legal test for liability in a civil suit, it fell short of the more stringent “beyond a reasonable doubt” test of guilt in a criminal case.

Now it seems that the steadily strengthening body of evidence about the human connection with global warming is at least approaching the higher standard and may already have satisfied it.

The second element of the sea change, if such it is, consists of a demonstrably heightened awareness and concern among Americans about global warming. The awakening has been energized largely by dramatic reports on the melting Arctic and by fear — generated by the spectacular horror of Hurricane Katrina — that a warmer ocean is making hurricanes more intense.

Politicians are weighing in on the subject as never before, especially with the advent of a Democratic-led Congress. It appears likely, if not certain, that whoever is elected president in 2008 will treat the issue seriously and act accordingly, thereby bringing the United States into concert with most of the rest of the world. Just last week, Senator John McCain of Arizona, a presidential aspirant and the co-author of a bill mandating stronger action, asserted that the argument about global warming “is over.” Back in the day, such words from a conservative Republican would have been unimaginable, even if he were something of a maverick.

I’ve been avidly watching from the sideline as the strengthening evidence of climate change has accumulated, not least the discovery that the Greenland ice cap is melting faster than had been thought. The implications of that are enormous, though the speed with which the melting may catastrophically raise sea levels is uncertain — as are many aspects of what a still hazily discerned climatic future may hold.

Last week, in its first major report since 2001, the world’s most authoritative group of climate scientists issued its strongest statement yet on the relationship between global warming and human activity. The Intergovernmental Panel on Climate Change said the likelihood was 90 percent to 99 percent that emissions of heat-trapping greenhouse gases like carbon dioxide, spewed from tailpipes and smokestacks, were the dominant cause of the observed warming of the last 50 years. In the panel’s parlance, this level of certainty is labeled “very likely.”

Only rarely does scientific odds-making provide a more definite answer than that, at least in this branch of science, and it describes the endpoint, so far, of a progression:

¶In 1990, in its first report, the panel found evidence of global warming but said its cause could be natural as easily as human.

¶In a landmark 1995 report, the panel altered its judgment, saying that “the balance of evidence suggests a discernible human influence on global climate.”

¶In 2001, it placed the probability that human activity caused most of the warming of the previous half century at 66 percent to 90 percent — a “likely” rating.

And now it has supplied an even higher, more compelling seal of numerical certainty , which is also one measure of global warming’s risk to humanity.

To say that reasonable doubt is vanishing does not mean there is no doubt at all. Many gaps remain in knowledge about the climate system. Scientists do make mistakes, and in any case science continually evolves and changes. That is why the panel’s findings, synthesized from a vast body of scientific studies, are generally couched in terms of probabilities and sometimes substantial margins of error. So in the recesses of the mind, there remains a little worm of caution that says all may not be as it seems, or that the situation may somehow miraculously turn around — or, for that matter, that it may turn out worse than projected.

In several respects, the panel’s conclusions have gotten progressively stronger in one direction over almost two decades, even as many of its hundreds of key members have left the group and new ones have joined. Many if not most of the major objections of contrarians have evaporated as science works its will, although the contrarians still make themselves heard.

The panel said last week that the fact of global warming itself could now be considered “unequivocal,” and certified that 11 of the last 12 years were among the 12 warmest on record worldwide. (The fact of the warming is one thing contrarians no longer deny.)

But perhaps the most striking aspect of the 2007 report is the sheer number and variety of directly observed ways in which global warming is already having a “likely” or “very likely” impact on the earth.

In temperate zones, the frequency of cold days, cold nights and frosts has diminished, while the frequency of hot days, hot nights and heat waves has increased. Droughts in some parts of the world have become longer and more intense. Precipitation has decreased over the subtropics and most of the tropics, but increased elsewhere in the Northern and Southern Hemispheres.

There have been widespread increases in the frequency of “heavy precipitation events,” even in areas where overall precipitation has gone down. What this means is that in many places, it rains and snows less often but harder — well-documented characteristics of a warming atmosphere. Remember this in the future, when the news media report heavy, sometimes catastrophic one-day rainfalls — four, six, eight inches — as has often happened in the United States in recent years. Each one is a data point in an trend toward more extreme downpours and the floods that result.

All of these trends are rated 90 percent to 99 percent likely to continue.

The list goes on.

And for the first time, in the wake of Hurricane Katrina, the panel reported evidence of a trend toward more intense hurricanes since 1970, and said it was likely that this trend, too, would continue.

Some of the panel’s main conclusions have remained fairly stable over the years. One is that if greenhouse gas emissions continue unabated, they will most likely warm the earth by about 3 to 7 degrees Fahrenheit by the end of this century, with a wider range of about 2 to 12 degrees possible. The warming over the Northern Hemisphere is projected to be higher than the global average, as is the case for the modest one-degree warming observed in the last century.

The projected warming is about the same as what the panel estimates would be produced by a doubling of atmospheric concentrations of greenhouse gases, compared with the immediate preindustrial age. It would also be almost as much warming as has occurred since the depths of the last ice age, 20,000 years ago.

Some experts believe that no matter what humans do to try to rein in greenhouse gas emissions, a doubling is all but inevitable by 2100. In this view, the urgent task ahead is to keep them from rising even higher.

If the concentrations were to triple, and even if they just double, there is no telling at this point what the world will really be like as a result, except to speculate that on balance, most of its inhabitants probably won’t like it much. If James E. Hansen, one of the bolder climate scientists of the last two decades, is right, they will be living on a different planet.

It has been pointed out many times, including by me, that we are engaged in a titanic global experiment. The further it proceeds, the clearer the picture should become. At age 71, I’m unlikely to be around when it resolves to everyone’s satisfaction — or dissatisfaction. Many of you may be, and a lot of your descendants undoubtedly will be.

Good luck to you and to them.