By Renee Schoof

McClatchy News Service

WASHINGTON – Doing nothing about global warming would cost America dearly for the rest of this century because of stronger hurricanes, higher energy and water costs, and rising seas that would swamp coastal communities, says a new study by economists at Tufts University.

The study concludes that it would be cheaper to take aggressive action to cut greenhouse gas emissions than it would be to suffer the consequences of a changing world. "The longer we wait, the more painful and expensive the consequences will be," the report states.

The Senate in early June will consider legislation to set a declining limit on emissions and establish a market for pollution permits that would reward companies that reduce pollution. The system is designed to reduce total U.S. emissions by 66 percent from 1990 levels by 2050.

"Most of the debate we expect will be about how much it will cost to implement the bill. This report provides the other side of the ledger – how much it will cost if we don't act," said Dan Lashof, director of the climate center at the Natural Resources Defense Council, an environmental group that commissioned the study.

The Tufts study includes a "bottom-up" analysis of the economic impacts in four categories and says that by 2100, annual costs would be $422 billion in hurricane damage; $360 billion in real estate losses, with the biggest risk on the Atlantic and Gulf coasts, particularly Florida; $141 billion in increased energy costs; and $950 billion in water costs, especially in the West. (The estimates are expressed in today's dollars.)

That adds up to an annual loss by 2100 of 1.8 percent of gross domestic product, or GDP, the sum of the nation's output of goods and services.

The study's "business as usual" scenario, in which greenhouse gas emissions continued at an increasing rate, was taken from the high end of likely outcomes of inaction described by the Nobel Prize-winning Intergovernmental Panel on Climate Change last year. The Tufts study also incorporated some later scientific findings.

The study projects that the average temperature will increase by 13 degrees Fahrenheit in most of the United States and 18 degrees in Alaska in the next 100 years, intensifying heat waves, hurricanes and droughts.

The report also forecasts stronger hurricanes as a result of higher sea surface temperatures; sea level rises of 23 inches by 2050 and 45 inches by 2100 that would inundate low-lying coastal areas; and higher air-conditioning bills in the Southeast and Southwest that wouldn't be offset nationally by lower heating bills in the North.

The authors of the Tufts study also used a revised version of the model used by Nicholas Stern for his 2006 assessment of the cost of inaction on a global scale. Using that model, the Tufts economists found a U.S. loss of 3.6 percent of GDP by 2100.

There have been more than six studies of the cost of reducing U.S. greenhouse gas emissions as outlined in the bill that will be debated in the Senate. All use different assumptions and have different outcomes.

None of these studies looked at the costs of not acting, said Eileen Claussen, president of the Pew Center on Global Climate Change, which recently examined some of these studies.

The Pew Center economists found that many of the studies of the costs of reducing emissions disregard cost-saving technologies and programs. They also said that all models of the costs predict that if the measures outlined in the bill were put into effect, the economy would continue to grow. The costs would be felt as a reduction of future growth.

Frank Ackerman, an economist at Tufts who was one of the main authors of that study, said the impact of climate change would be worse than what his numbers showed "because of the human lives and ecosystems that will be lost and species that will be driven into extinction – all these things transcend monetary values."

Scientists already can observe signs that the Earth is warming, including diminishing summer ice in the Arctic Ocean, drier conditions in the West and more severe droughts and storms, Lashof said. Most of the dangerous changes that are predicted can be avoided, he added, "but our window of opportunity is closing very rapidly."