U.N. report spells out U.S. warming impacts

updated 1:03 p.m. ET April 11, 2007

UNITED NATIONS - Chicago and Los Angeles will likely face increasing heat waves. Severe storm surges could hit New York and Boston. And cities that rely on melting snow for water may run into serious shortages.

These are some of the findings about North America in the report finished last week by hundreds of scientists that try to explain how global warming is changing life on Earth. The scientists with the Intergovernmental Panel on Climate Change released a summary of their findings on global warming last Friday and outlined details of the report focusing on various regions on Tuesday.

According to the panel, global warming is already having an effect on daily life but when the Earth gets a few degrees hotter, the current inconvenience could give way to danger and even death. The North American impact will be felt from Florida and Texas to Alaska and Canada's Northwest Territories.

"Canada and the United States are, despite being strong economies with the financial power to cope, facing many of the same impacts that are projected for the rest of the world," said Achim Steiner, executive director of the U.N. Environment Program, which co-founded the panel.

He said the findings underline that the best way to reduce the effects of global warming is "deep and decisive cuts in greenhouse gas emissions to avoid dangerous climate change in the first place."

Tension over water
The panel warned that shifts in rainfall patterns, melting glaciers, rising temperatures, increased demand and reduced supplies of water in some places are likely to increase tensions between users — industry, agriculture and a growing population.

"Heavily-utilized water systems of the western U.S. and Canada, such as the Columbia River, that rely on capturing snowmelt runoff, will be especially vulnerable," the report said.

A temperature warming of a few degrees by the 2040s is likely to sharply reduce summer flows, at a time of rising demand, it said.

By then, the panel estimated that Portland, Ore., will require over 26 million additional cubic meters of water as a result of climate change and population growth, but the Columbia River's summer supply will have dropped by an estimated 5 million cubic meters.

Meanwhile, it said, just over 40 percent of the water supply to Southern California is likely to be vulnerable by the 2020s due to losses of the Sierra Nevada and Colorado River basin snow packs.

The panel also said "lower levels in the Great Lakes are likely to influence many sectors" and exacerbate controversies over diverting water to cities such as Chicago, and the competing demands of water quality, lake-based transport, and drought mitigation.

NYC, Boston flooding cited
Cities could also be at risk from high tides and storm surges, it said.

Near the end of the 21st century, under a strong warming scenario, the New York City area could be hit by increasingly damaging floods from surges, "putting much of the region's infrastructure at risk," the panel said. A current one in 100 year flood in New York could have a return period of three to four years, it added.

By the 2090s in New York, a one in 500 year flood could be a one in 50 year event “putting much of the region’s infrastructure at risk.”

Boston's transportation network may also be at risk from a sea level rise and the increased probability of a powerful storm surge, it said.

As for the impact of rising temperatures, the panel said a 25 percent increase in heat waves is projected for Chicago later this century, while the number of heat-wave days in Los Angeles is projected to increase from the current 12 per year to between 44 and nearly 100.

By the mid-21st century, regions in Alaska and Canada's Northwestern Territories are likely to be at "moderate to high risk" due to coastal erosion and thawing of permafrost, the report said.

North American producers of wood and timber could suffer losses of between $1 billion and $2 billion a year during the 21st century if climate change also sparks changes in diseases, insect attacks and forest fires, the panel said.

Other points made in the report include:

• Groundwater flows from the Edwards Aquifer in Texas could drop by up to 40 percent, leading to problems for farmers.
• The Ogalla Aquifer — a shallow formation below South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico and Texas — could see natural recharge drop by 20 percent.
• The costs of replenishing Florida’s beaches with sand, in order to counter a sea level rise of a foot, could be between $2-9 billion.

• A reliable snowmobile season is likely to disappear from most of eastern North America by the 2050s, jeopardizing the $27 billion snowmobiling industry.

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