Sea levels likely to rise 25cm this century

Greenhouse gases are to blame, according to new studies on global warming from the National Center for Atmospheric Research.

No matter what happens, sea levels and temperatures are going to rise over the next century, according to a pair of reports out of the National Center for Atmospheric Research.

Global warming will likely cause the sea level to rise by about 25cm, or close to a foot, by 2100, while average temperatures will rise by at least a half degree Celsius, according to Tom Wigley, a researcher at the agency and an author of one of the studies released today. Researcher Gerald Meehl wrote the other.

Tom Wigley
Tom Wigley,

Wigley added that global warming is caused by greenhouse gases like carbon dioxide pumped into the atmosphere by human activity. Even if humans stopped pouring greenhouse gases into the atmosphere today, sea levels will rise by 11 centimeters (about 4 inches) over the next century at a minimum, the studies predicted.

"That is an extreme lower bound of what might happen," Wigley said. "More likely, the sea level rise will be considerably greater."

A worst-case scenario predicts a 30-centimeter rise in sea level and a world temperature rise of 3.5 degrees Celsius. Worldwide sea levels rose by 5 centimeters in the 20th century, when human-induced global warming began to be tracked.

The inevitable nature of climate change comes as a result of two factors: the long lifetime of carbon dioxide in the atmosphere, and the fact that water heats and cools more slowly than air. Carbon dioxide, which is increasing in the atmosphere, traps sunlight, which then heats the ocean, which in turn rises and expands.

While Northern Europe and the United States would be able to adapt to a 25-centimeter rise in sea level, poor countries in coastal areas could face huge problems. Bangladesh, for instance, is sandwiched between the snow melt from the Himalayas and tropical storms from the Bay of Bengal. Elevated temperatures and sea levels could dramatically increase the impact of storms.

By 2400, barring major changes, worldwide sea levels could rise by 100 centimeters. "A meter sea level rise would have a lot of major consequences for many parts of the world," Wigley said.

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