The Heat Is Online

Press Accounts of US National Climate Change Assessment

Warming Effects to Be Widespread

Significant Changes for U.S., Good and Ill, Seen in Study

By Andrew C. Revkin, The New York Times, June 12, 2000

Warming of the global climate is likely to have substantial consequences -- for better and worse -- around the United States in coming decades, including bumper crops in the heartland, chronic erosion of coasts, summer water shortages and winter floods in the West and a future New York City that steams in summer like present-day Atlanta.

These are a few of the predictions made in the first thorough federal assessment of the possible effect on the country, region by region, of a warming trend that many scientists expect will characterize coming decades.

Increasingly, mainstream scientists are concluding that a buildup of heat-trapping gases like carbon dioxide in the atmosphere has contributed to warming in the last 100 years, and they say the trend is likely to carry well into the new century.

Some of the growth in these so-called greenhouse gases, scientists say, is caused by the burning of fossil fuels, destruction of forests and other human activities.

Temperatures nationwide rose about one degree in the 20th century, and the report estimated the potential effects of further warming by using a "business as usual" assumption, in which carbon dioxide levels continued to grow at the rate of recent years. At this pace, the average temperature in the country would rise 5 to 10 degrees in the next century, although the authors stressed that this was only one possibility. To put that in perspective, the world is 5 to 9 degrees warmer than in the last ice age, 18,000 to 20,000 years ago.

The study, which is to be released today by the Clinton administration for 60 days of public review, was ordered by Congress in 1990 to help lawmakers identify vulnerabilities and potential benefits of the warming trend. But it kicked into high gear only three years ago, when computer models grew sophisticated enough to analyze links between the atmosphere and oceans and local systems like crops and forests.

The assessment includes an illustrated summary and a series of technical analyses of the effect of a warmer world on forestry, fresh water, farming, coasts and human health. The report will be on the Internet at

The report forecasts some profound changes, with many regions of the country seeing conditions shift to those of their present-day neighbors to the south.

In the mountains of the Pacific Northwest, rising stream temperatures are very likely to harm migrating salmon, the report said.

In California, less snow in winter would lead to less runoff from melting snow in the late spring, reducing water supplies during the summer growing season. The Southwest would see rising precipitation that could cause shrubby forests to overtake desert landscapes.

The study says one of the most likely of all consequences from continued warming would be coastal erosion and destructive storm surges as sea level steadily rises.

In Eastern cities, the summer heat index, combining humidity and temperature, is likely to rise, so that as New York City takes on Southern steaminess, Atlanta will see hot spells more typical of Houston.

The biggest benefits are likely to come from the positive effect of rising carbon dioxide concentrations on plants, which rely on the gas for photosynthesis. Using computer models of climate, crops and forest health, the study found that the country could see rising yields and falling prices for food and timber. The falling prices would be good for consumers but could hurt some timber companies and farmers as already tenuous profit margins shrink.

But scientists who conducted the study cautioned that the benefits would not be uniform. For example, while farmers in the Northern plains could see gains, those in Southern states could see losses because of increased risk of droughts and damaging floods as more rain falls in drenching downpours.

The good news should be tempered, too, because the study did not calculate possible agricultural losses because of flourishing weeds or migrating insect pests, its authors said.

And the composition of wild forests is likely to change, with some species that are considered hallmarks of particular regions disappearing. For example, the sugar maple, the New York state tree and an important species for tourism, is likely to vanish from all but the most northern parts of the state as its preferred colder climatic zone moves north.

The warming is likely to keep shipping lanes in Alaska and the Great Lakes free of ice longer, easing the movement of oil and other goods.

But other effects could negate any savings, the study concluded. Water levels in the Great Lakes are expected to drop, increasing the need for costly dredging of channels.

In Alaska, the effects of the warming have already been felt and are requiring costly adjustments, with roads and air strips requiring constant repair as underlying permafrost thaws and buckles, scientists said. Native Alaskans, who rely on ice-dwelling seals for food, are finding it more difficult to hunt, said Gunter Weller, a climatologist at the University of Alaska Fairbanks, who is participating in the project.

"For the native community or the oil industry or the fishing industry, this is no longer some nebulous global thing coming in 100 years," Dr. Weller said. "These are real things in real time that are really occurring."

Scientists from dozens of government agencies, universities, private groups and industries conducted the studies and more than 300 independent reviewers offered comments, the authors said. The overview's three principal authors were Dr. Thomas R. Karl, director of the National Climatic Data Center in Asheville, N.C.; Anthony Janetos of the World Resources Institute in Washington; and Dr. Jerry M. Melillo of the Marine Biological Laboratory in Woods Hole, Mass.

As the overview moved from early to final drafts in the last few months, the politics of climate intruded, with intense tugs of war being felt by some scientists involved in the work over how to word conclusions.

Indeed, in recent weeks the emphasis changed, participants said, with the focus shifting somewhat toward the positive consequences for agriculture, for example.

Also, the 145-page overview was released even though not all the underlying regional studies are complete, a decision that drew criticism from scientists from both ends of the political spectrum.

"There's been pressure all along that the synthesis had to come out first because of the election," said a scientist who shares the Clinton administration position that global warming is a serious problem, but who is still involved in the report and thus spoke only on condition of anonymity. "It's unfortunate, because the whole process would have been stronger if you did it the right way. Then the critics wouldn't have anything to say."

Over the weekend, officials at the White House said the summary was released ahead of time only because the final work on some of the underlying studies had been delayed.

Apart from the timing, a variety of experts involved in preparing the document, including people from industry and advocacy groups, say it represents a real consensus and that its findings are significant.

Thomas F. Cecich, vice president for environmental safety at the drug company Glaxo Wellcome and a member of the team that wrote the national overview, called the report a first look at a dizzyingly complicated system. He said that everyone involved tried to filter out politics and preconceptions. "I think it's been a fair and open and scientifically valid process," he said.

In particular, many scientists said, the effort, if continued and refined, could offer the first opportunity for the country to incorporate long-term climate projections into its planning for everything from bridge building to crop planting.

The report concludes that society, for the most part, will probably be able to adapt to many of the coming shifts, but that some natural systems -- alpine meadows, coral reefs, mangrove swamps and the like -- will be damaged or disappear because they are either hemmed in by man-made structures or geography or simply cannot keep pace with the rate of temperature change.

The authors stressed that the consequences described in the study -- like the visions of Scrooge's future in "A Christmas Carol" -- mainly represent developments that may be, not things that must be.

And there will always be surprises, said Dr. Karl, one of the main authors. "There are a lot of uncertainties with respect to interactions between natural systems, human systems and climate."

Even if the surprises are good news, he said, humans will not necessarily be able to exploit them. "Usually, if something is not anticipated, you can't take advantage of it."

Report predicts major climate change

Drought, floods, erosion forecast in federal study

By Curt Suplee, The Washington Post, June 12, 2000

Global warming in the 21st century will likely cause drastic changes in the climate of the United States, including potentially severe droughts, increased risk of flood, mass migrations of species, substantial shifts in agriculture and widespread erosion of coastal zones, a new federal report says.

Yet "for the nation as a whole, direct economic impacts are likely to be modest," concludes the report, which is based on computer models and historical data, and "American society would likely be able to adapt to most of the impacts," although "particular strategies and costs [are] not known."

"Climate Change Impacts on the United States," scheduled for public release today after four years of preparation, has an ample array of ominous projections:

Average temperatures will probably rise 5 to 10 degrees Fahrenheit — nearly twice the projected warming for the planet as a whole — prompting more summer urban heat waves and gentler winters across the nation.


Agricultural production will likely surge, and forests will probably flourish, thanks to the fertilizing effect of more carbon dioxide in the air. But many long-suffering ecosystems, such as alpine meadows, coral reefs, coastal wetlands and Alaskan permafrost, will likely deteriorate further. Some may disappear altogether.

Snowpack will probably diminish by 50 percent on average, while winter rains increase, bringing 60 to 100 percent more showers to much of Southern California and the parched Southwest.

Total precipitation nationwide, which rose 5 to 10 percent during the 20th century, will probably increase another 10 percent by 2100, chiefly in the form of extreme storms, exacerbating runoff pollution in the Chesapeake Bay and other sensitive areas.

Paradoxically, however, the threat of drought — especially in the western Kansas-eastern Colorado breadbasket — will rise because hotter conditions enhance evaporation. For the same reason, water levels could drop as much as five feet in the Great Lakes.


As for health effects, the report projects doubling or tripling of heat-related deaths in Minneapolis, Chicago and other cities that rarely experience extreme high temperatures. The July heat index is likely to rise by 10 to 20 degrees in the mid-Atlantic region.

Warming may also cause substantial shifts in the habitats of disease-bearing mosquitoes and other animal sources of disease. But the authors conclude that "not enough is known about our adaptive capabilities to say whether or not climate changes will make us more vulnerable to health problems."

The report, known as the "national assessment," was ordered by Congress in 1990 and assembled by the U.S. Global Change Research Program, an executive branch initiative incorporating projects in nine federal agencies and the Smithsonian Institution. The first such comprehensive effort by any country, it will be available for public review at and elsewhere as part of a long-term effort to understand and plan for the effects of climate change.

"We're not making a specific prediction about what the future will be like. It would be farcical to try to do that," said Anthony Janetos of the World Resources Institute, co-chairman of the 14-member panel that wrote the 145-page overview. (An additional 700-page "foundation document" provides scientific details.) Instead, "given our current understanding, these are reasonable scenarios of how the future might play out."

The report employs conventional assumptions, such as an annual increase of 1 percent in the amount of greenhouse gases in the atmosphere. It assumes that sea levels — which have risen four to eight inches globally over the past century — will rise an additional five to 35 inches by 2100. A 20-inch rise, the authors say, would eliminate about 4,000 square miles of coastal wetlands in addition to the nearly 2,000 square miles lost in the past half-century.

The analysis is based largely on two computer simulations of future climate (from the Canadian Meteorological Centre and the Hadley Centre in the United Kingdom) that often produce very different or even antithetical results.


For example, climate-change skeptic S. Fred Singer of the Science & Environmental Policy Project in Fairfax said, "look at North Dakota. One [model] turns it into a desert, the other into a swamp. Neither will probably happen." Central Kansas shows an increase in soil moisture of 25 percent in one projection; in the other, it loses 50 percent. North and South Carolina have dramatic rainfall increases in one model, and decreases of up to 10 percent in the other.

Such discrepancies are common among sophisticated computer climate models, each of which represents the interactions among heat, air, water, cloud and land somewhat differently. The smaller the geographic scale, the larger the disparities can be.

"But we can't just say, 'Well, this is hard. Therefore we can't say anything,' " Janetos said. "There are a lot of local and regional decisions that have to be made now — not just federal policies — and people have to start thinking hard about what they might want to do."

The model contradictions are enough to "make you tear your hair out," said Tom Wigley of the National Center for Atmospheric Research, who was not involved in the report. "At the regional level, there's a tremendous amount of uncertainty."

Nonetheless, he said, even "model results that are radically different" serve to notify residents that "there's a good chance that we're in for a big change in the future, but we don't know what direction it's in."

Several environmental groups hailed the report as a timely warning. "America's alarm bells should go off today," said Jennifer Morgan of the World Wildlife Fund.

But numerous skeptics feel that the language is strongly biased toward negative conclusions. That was also the initial reaction of some staff and external reviewers.

"I think we have fixed most of that problem," Janetos said. "We've made an enormous effort to be balanced."

Not everyone will agree. For example, in the forestry section, the analysis indicates that even in the Southeast, where the likelihood of drought stress during the next century is considered fairly high, timber stands will increase by 8 percent to 25 percent depending on species. Yet the strong emphasis in the text is on the threat of reduced producer profits as more trees bring prices down.

Similarly, the section on agriculture projects 15 to 50 percent yield increases for nearly all commercial crops, including wheat, rice, barley, oats, potatoes and most vegetables. That would entail the use of 5 to 20 percent more pesticides, the report suggests, and would raise the threat of more nitrogen-fertilizer runoff into bays and estuaries. But the net effect would be extraordinary.

Moreover, the analysis suggests that a warmer, accelerated growing season and increased rainfall nationally will probably reduce the need for crop irrigation 30 to 40 percent by the end of the 21st century. That would be a huge change in a nation where more than 80 percent of all fresh water now goes to agricultural uses.

Yet the text notes laconically that climate change probably "will not imperil the ability of the U.S. to feed its population and to export foodstuffs."

Janetos is looking forward to hearing all comments. "This is a serious issue. It's not ideological," he said. "There is a wide range of changes coming around the country, and we have to start thinking about that. My hope is that [millions of Americans] will take a look at this assessment. I'd love for this Web site to set new records."

© 2000 The Washington Post Company

U.S. Study on Global Warming Paints a Dire Weather Portrait

By John J. Fialka, THE WALL STREET JOURNAL, May 26, 2000

-- Long-Range U.S. Forecast: Heavy rains, severe droughts, improved growing conditions for some farmers and the end of winter as we know it.

WASHINGTON -- A draft overview of a soon-to-be-released federal report on global warming paints something like that dire picture. Rising sea levels and heavy rains, for example, will force coastal cities to spend billions of dollars to redesign subways, tunnels, dams and sewage-treatment systems.

It is too gloomy, some federal experts complain. They want the overview revised to reflect more of its positive findings. The 118-page overview of the report, called "Climate Change and America," also predicts that farmers in the northern half of the nation may be able to capitalize on longer growing seasons by planting more than one crop.

More Drafts of Overview to Come

"I think some people get caught into a groove," says Peter Sousounis, a University of Michigan meteorologist in Ann Arbor who led the Great Lakes regional team that contributed to the report. He and others have argued that the final report should pay more attention to the economic "winners" of climate change. He says later drafts of the overview, scheduled to be released next month, should reflect some of these objections.

Until now, the debate on the impact of global warming has been focused on planetwide changes. While a few scientists still argue that the warming will be slight but beneficial, most see an elaborate mix of changes, some good and some bad. The coming rise in average temperatures, they predict, will break climate patterns that have held for centuries.

The report is the first attempt to predict the impact of global warming on various regions in the U.S. during the next hundred years. The four-year effort has involved 5,000 people and a total of nine government agencies.

The overview is an attempt by a White House "national assessment synthesis team" to summarize the findings of a much more complex, 700-page report prepared by the experts. Illustrated with multicolored graphs and written in relatively simple language, the overview is intended to bring home the impact of climate change to the average American, who, polls show, has given little attention to the issue so far.

A copy of an initial draft dwells largely on the economic downside. Using two computer models, for instance, the draft predicts average temperatures could rise between five and 10 degrees Fahrenheit by the end of this century. It says increased evaporation could lower the already-falling level of the Great Lakes by as much as 5 feet, requiring expensive reconstruction of ship docks and canal locks.

The health section of the overview predicts that a combination of higher temperatures and heavy rains will trigger the spread of waterborne diseases and red tides -- an algae-like, poisonous microorganism that lives in salt water and kills fish. It also predicts a northward expansion of malaria, dengue fever and other diseases spread by mosquitoes and ticks.

Two EPA Scientists Object

The forecast provoked an objection from two Environmental Protection Agency scientists who wrote the underlying health report. Mike Slimak and Joel Scheraga argued that the descriptions "have a rather extremist/alarmist tone," which doesn't reflect the scientific papers that the overview supposedly summarized. A spokesman for the EPA says the two men, who could not be reached for comment, "are happy" with the wording of a later draft.

Mr. Sousounis objected that the economic gloom and doom in the overview overlooks huge positive effects, such as the easing of fierce winter conditions in the Midwest. He notes that the costs of energy, snow removal, accidents and the health impacts of cold weather should drop sharply.

Jae Edmonds, an economist who earlier developed a model of the economic impact of climate change for the White House, complains that the overview "chronicles a series of possible calamities that the various authors have happened upon," with an occasional aside that the "problem might not be so bad."

Dr. Edmonds, who works for the Department of Energy's Pacific Northwest National Laboratory, argues that the final report should contain a more balanced view of "winners and losers," and man's ability to adapt to changing conditions over time.

Experts from industry were also asked to comment. Russell Jones, a senior economist for the American Petroleum Institute, complains of too much reliance on computer models. He says he and other volunteer reviewers could not get access to scientific reports reflected in the overview. "We were frustrated," he says.

Neal Lane, a physicist who is science adviser to President Clinton, is managing the ompilation of the report and the delicate job of drafting an overview that captures the complex issue.

"This hasn't been done before. It's been an extremely challenging, exhaustive process," Dr. Lane says. He adds that more than 400 reviewers will have read at least parts of it before it is released. Asked about the fight among the experts over the need to present a balanced view, Dr. Lane says the final draft will say more about the benefits of warmer winters and more robust crops in some regions.

"But if at the same time, parts of your coastal regions are going underwater and other parts of the world are becoming destabilized because of hunger and disease, how good a world would that be?" he asks.

University of Massachusetts climatologist Ray Bradley in Amherst recently developed a graph of average temperature variations going back thousands of years, using ice-core samples, tree rings and other data to estimate the temperature range before man measured it.

Climatologists call the graph "the Hockey Stick," because it shows a one- degree variation in average temperature until the end of the 20th century, when the graph line begins to curve straight up, like the blade on a hockey stick.

"All of our experience [with climate] from the Middle Ages on is trivial, compared with what's in store for us in this century," Mr. Bradley says.