Watch CBSN Live

Grim Forecast Or Just Hot Air?

Future Americans could be living in a world that looks and feels quite a bit different from the one we enjoy today.

That's according to a new study which used computer models to project the impact of a rise in the earth's temperature on the American landscape, agriculture, and human health.

The results of the 4-year-long study, commissioned by Congress, are expected to be made public next week but an overview report concludes "most Americans will experience significant impacts" if the earth warms from 5 to 10 degrees over the next 100 years, as some scientists predict.

A draft copy of the report, obtained by the Associated Press, says salmon could disappear from the Columbia River in the Pacific Northwest, sugar maples could become nothing but a memory in New England, and barrier islands off the Carolinas could be swept away by rising sea levels.

Trending News

It's the first ever region-by-region national assessment attempting to project the impact of climate changes in the U.S., as opposed to the earth as a whole.

AP Photo
The study says increased
rain caused by global
warming could bring more
greenery to Southwestern
desert landscapes.

The report acknowledges there are "significant uncertainties in the science underlying climate-change impacts," particularly when it comes to human health.

The study 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."

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.

"This document is an evangelistic statement about a coming apocalypse, not a scientific statement about the evolution of a complicated system with significant uncertainties," John Christy, a climatologist at the University of Alabama-Huntsville, wrote during a review of an early draft of the 128-page overview.

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 report, the work of hundreds of scientists both in and out of government, says entire ecosystems would likely shift northward as temperatures increase, and coastal areas would have to cope with rising seas and the prospect of more frequent storms. Cities would swelter in more frequent heat waves, and droughts would become more likely in parts of the Midwest.

The report also says the warmer, wetter climate would have a silver lining for farmers, as crop yields would increase in many areas. Tre growth would accelerate in the Northwest, but forests in the Southeast likely would break into "a mosaic of forests, savannas and grasslands."

AP Photo
Some scientists believe
the sugar maples could
someday disappear from
New England.

The warming would 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 still different problems.

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

Tree, fish and animal species would migrate northward everywhere, if the report's projections are on target.

In the Pacific Northwest, that would mean a farewell to scenes of salmon swimming upstream, as warm water in streams and offshore push salmon to cooler, more hospitable waters in Canada.

That's just a prediction from the report, but north of the U.S. border, in British Columbia, Vancouver, salmon stocks are already at their lowest point in a century. Both environmentalists and government officials say global warming is to blame. According to the Pacific Fisheries Resource Conservation Council, of the 9,600 types of British Columbia salmon, nearly 2,000 are either extinct or moderately threatened.

AP Photo
Global warming could spell
trouble for barrier islands
such as Oak Island on
the Outer Banks of North
Carolina, shown here after
Hurricane Floyd in 1999.

Rising temperatures could be a problem even in Alaska, according to the report, which says a few degrees more warmth would cause further thawing of permafrost, damaging roads and buildings.

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 would be likely to 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 would be much milder. The result: fewer opportunities to ski and more time for mountain hiking and other mild-weather recreation

The warmer weather would also 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.

CBS Worldwide Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report

View CBS News In