WASHINGTON—Rising sea levels due to global warming in the next few decades could put trillions of dollars in U.S. assets at risk, according to a report released Tuesday.

The joint report, released by German insurer Allianz S.E. and the World Wildlife Fund, said the planet’s atmosphere is close to dangerous temperature thresholds, or “tipping points,” that could cause devastating environmental and economic consequences.

According to the report, a sea level rise of 20 inches by 2050, as predicted by climate scientists, could jeopardize roughly $7.4 trillion of U.S. assets. About $1.4 trillion worth of U.S. coastal-area assets are at risk due to storm surge from a one-in-100-year event, the report said.

The report ranked Miami, New York, New Orleans and Boston among the U.S. cities with the greatest asset exposure by mid-century due to global warming effects.

In addition to rising sea levels, the report highlighted three other tipping points that are likely to have the biggest impact by mid-century: an increasingly arid climate in California, disturbances in the summer monsoon in India and Nepal, and the reduction in the Amazon rainforest due to drought.

The report called on world leaders to take “immediate action” at the upcoming United Nations-sponsored climate change summit in Copenhagen on Dec. 7.

Copyright © 2009 Crain Communications, Inc.