Scientists paint grim view of impact on U.S. of global warming

Assessment predicts results if nation’s weather warms by 5 degrees to 10 degrees over the next hundred years; Alaska would see further permafrost thawing

H. Josef Hebert

Associated Press Writer

A new climate study says if global warming continues, then the results could mean more thawing of the permafrost in Alaska causing damage to roads and impacting forests and fish.

It’s a grim forecast: Sugar maples in New England disappear, the barrier islands off the Carolinas are swept away by higher seas.

These changes in landscape and ecosystem are but a few of the projections outlined in the first-ever detailed “national assessment” of what could be expected to occur in the United States — region by region — if the nation’s climate becomes 5 degrees to 10 degrees warmer over the next 100 years.

The assessment, likely to be made public next week, is the product of four years of study, numerous workshops and reviews by hundreds of scientists both in and out of government who examined global warming’s likely regional impacts as well as its effect on human health, agriculture, forests and coastal areas across the country.

Unlike other studies that have examined general global impacts, this assessment was directed by Congress to focus on the United States specifically.

Critics argue the analysis is little more than guess work and that computer climate models, heavily relied upon in the assessment, cannot predict impacts on a regional basis.

Critics says study not scientific

Christy, who is among a group of scientists skeptical about the likelihood of significant global warming, did not return telephone calls seeking to know whether his views have changed about later drafts.

The overview report, a recent draft copy of which was obtained by The Associated Press, acknowledges “significant uncertainties in the science underlying climate-change impacts” particularly related to human health. Still, it concludes “based on the best available information, most Americans will experience significant impacts” from the Earth’s warming.

The forecast predicts “a complex mix of positive and negative impacts” and concludes there may be surprises. “It is very likely that some aspects and impacts of climate change will be totally unanticipated,” the report says.

Ecosystems will shift northward

At the same time, the warmer, wetter climate will cause larger crop yields for many farmers and cause tree growth to flourish in the Northwest, although forests in the Southeast likely will break into “a mosaic of forests, savannas and grasslands” and sugar maples could disappear from the Northeast.

The warming will cause ocean levels to rise, causing barrier islands to disappear and — when the geography allows — force wetlands and marshes inland. But the Great Lakes are predicted to decline because of increased evaporation, causing yet different problems.

Tree, fish and animal species will migrate northward everywhere.

In the Pacific Northwest, the salmon may shift farther north because of the warmer streams and offshore waters and be replaced by warmer-water species.

And in Alaska the rising temperature is expected to cause further thawing of the permafrost, damaging roads and buildings.

Some coastal cities, faced with sea level rise and more frequent storm surges, may have to redesign and adapt water, sewer and transportation systems, the study says. It makes no attempt to estimate the costs of such improvements.

An early draft of the overview summary was attacked in December as having “an extreme, alarmist tone” on predicting impact on human health. It since has been revised with more emphasis on the uncertainties of predicting health impacts.

Nevertheless, the study says higher temperatures and increased rainfall likely will exacerbate air pollution, saddle large cities with more frequent and severe heat waves, and lead to the spread of waterborne or insect-carrying diseases, including malaria in the Southeastern states.

In much of the country, winter will be much milder. The result: fewer opportunities to ski and more time for mountain hiking and other mild-weather recreation.

The warmer weather will reduce the mountain snowpack, cutting summer runoff that feeds irrigation across much of the West. More rain in the arid Southwest could bring new vegetation to desert lands, but also more flash floods.

UAF researchers say global warming may be harming spruce growth

Scientists trace global warming to buildup of carbon dioxide and other gases in the atmosphere. But they have reasoned that warmer temperatures would spur tree growth, which in turn would make the trees draw more carbon dioxide out of the atmosphere.

The growth of inland Alaska white spruces has declined, however, with warming temperatures, researchers from the University of Alaska Fairbanks said in the June 8 issue of the journal Nature.

The problem is that in this region, which is semiarid, climbing temperatures have produced drought stress on the trees since the 1970s, they said.

Their study used climate records and analysis of tree rings.

White spruce is one of the most common trees in the northern forests of western North America, they said. So the idea that warming will make those forests pull carbon dioxide from the atmosphere may be incorrect, which would lead scientists to underestimate future concentrations of the gas, they said.