How it'll affect you (if you're an American)

From an excerpt in the UN report:

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.

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.

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.

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.

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.

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