Published on Monday, June 12, 2000 in the Washington Post
'America's Alarm Bells Should Go Off' As Drastic Climate Changes Forecast
by Curt Suplee
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 are likely to 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 http://www.usgcrp.gov 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 contend 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."
From the Report
Among the likely effects of warming over the next century:
Northeast: Winter nights will be as much as 9 degrees warmer, and annual precipitation is likely to increase. With higher sea levels, storm surges will threaten beaches in New Jersey and imperil bridges and other transportation system elements.
Southeast: In one model, it dries considerably, forests gradually turn to savannah, and heat waves and drought scourge the region. In the other, rainfall increases as much as 25 percent, forests thrive (especially hardwoods) and crop yields rise, while the risk of flood damage increases substantially.
Midwest/Great Plains: Risk of drought is substantial. A projected increase of 10 to 30 percent in rainfall is expected to be more than offset by evaporation and loss of soil moisture. Depending on the model, Illinois in 2100 will have a summer climate equivalent to that now seen in Oklahoma or North Carolina. Fish populations will shift to warm-water species.
California/Southwest: Temperatures rise, but rainfall may double, with grasslands and even forests forming in parts of Nevada and Arizona. That could be of enormous importance to the region, where population is rising fast.
Northwest: Snowpack is projected to decline from 10 to 70 percent in parts of Oregon, Idaho, Montana and Wyoming, with likely increases in soil moisture for parts of Oregon and Idaho.
Effects on environment
The composition of tree species changes, altering animal habitats. In the Southeast, woodlands and grasslands displace forests if the climate becomes drier.
Invasive, nonnative species increasingly thrive. In the West, woodlands and forest displace grasslands if the climate becomes wetter.
A rise in water temperature and changes in the timing and amount of runoff alter habitats in rivers and lakes.
Coastal and marine
Rising sea levels reduce coastal wetlands. Changes in quantity and quality of fresh water entering streams and bays alter habitats. In Alaska, ice changes affect habitats.
SOURCE: U.S. Global Change Research Program