Drastic Climate Changes Forecast
By Curt Suplee
Washington Post Staff Writer
Monday, June 12, 2000; Page A03
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."
SOURCE: The Washington Post
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