Greenhouse gas emissions in the United States may grow faster in the next 50 years than they have in the past 50, and higher energy prices will curb the problem better than technology, two economists say.

Despite many technological advances in the past half-century, the rates of growth of energy use and of greenhouse gas emissions have continued to rise (by about 2.2 and 1.6 percent per year respectively), despite the rising costs of energy, Richard Eckaus of MIT and Ian Sue Wing of Boston University found in a new study.

"We found that, in spite of increasing energy prices, technological change has not been responsible for much reduction in energy use, and that it may have had the reverse effect," Eckaus said.

Another recent study showed that carbon dioxide levels in the atmosphere were rising faster than expected because inefficient technologies were on the rise in developed countries such as China and because the natural mechanisms for sucking up and storing carbon, called carbon sinks, were essentially being exhausted.

In the new study, funded by the U.S. Department of Energy and the Harvard Kennedy School of Government in Massachusetts, Eckaus and Sue Wing examined the periods of 1958 to 1996 and 1980 to 1996 and then used computer models to project changes in the growth rates of both energy use and emissions from 2000 to 2050. Their findings, detailed in the November issue of the journal Energy Policy, showed that these rates may accelerate.

"The rates of growth could be higher by a half percent or more, which becomes significant when compounded over 50 years," Eckaus said.

The Intergovernmental Panel on Climate Change released a report this weekend that warned of the hazards that rising carbon dioxide levels will cause, noting that even if reductions are made, certain effects, such as sea level rise, will still occur.

Technological advances may not be a fix even though they have been looked to as a source of curbing emissions of carbon dioxide and other greenhouse gases, Eckaus said, citing the U.S. steelmaking industry as an example.

Though steelmakers' furnaces are now electrical, reducing coal use at the steel plant, some of the electricity that powers the furnaces is still generated by coal, resulting in more carbon dioxide emissions.

Instead of relying on technology to solve the global warming problem, governments should make energy more expensive, Eckaus advises.

"There is no 'a priori' reason to think technology has the potential for reducing energy use while meeting the tests of economics," he said. "It's politically unappetizing in the U.S., but in Europe, gas costs $6 a gallon. Make energy more expensive: People will use less of it."

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