Just because power such as solar heat, wind and geothermal are not exhaustible, many mistakenly believe they pose little or no environmental risk.

Consider large wind turbines, the world's fastest growing source of electricity. Denmark meets 20 percent of its energy needs by harnessing the wind. India produces even more electricity from turbines. China is on track to have a 5,000 megawatt capacity by 2010.

The energy contained in the worldwide swirling of the lower atmosphere is enormous. Christina Archer and Mark Jacobson at Stanford University have created a global wind energy resource map that estimates the global potential for turbine power at 72 terawatts, 40 times the world's energy consumption in 2000.

It is the very magnitude of this power that has begun to raise some questions about the weather-related implications of harnessing wind. The laws of thermodynamics tell us that if energy is produced by a turbine, the wind passing over it must be slowed. While the effect today is negligible, a crash program to harvest wind power might have serious climatic consequences.

In one of the first studies to get at this issue, scientists at Princeton modeled the likely impact of a large wind farm on the Great Plains. Lead author Somnath Baidya Roy reported in the Journal of Geophysical Research that turbines pushing warm air across moist and cool soil overnight would significantly raise morning temperatures in their region.

In a separate study, David Keith of the University of Calgary estimated the drag from a worldwide deployment of wind farms would produce both cooling in polar regions above 60 degrees North latitude and warming in temperate regions.

Evidence also suggests that turbines amplify desiccation in fragile desert areas, where American wind farms are typically located. A study of ground squirrels by the University of California at Davis found those living near wind turbines exhibited signs of increased stress.

Questions have been raised about the environmental impact of recycling the 100-meter wide blades that will periodically need to be removed from the largest rotating machines ever built.

"In our haste to cash in on the obvious environmental benefits of wind power," concludes Ed Douglas in the July 8, 2006, issue of New Scientist, "we are largely ignoring the ecological damage that turbines can do. ... (They) could disrupt fragile ecosystems and even contribute to global warming."

Even the act of constructing a wind turbine can be ecologically damaging. It turns out, for example, that the peat bogs where many European wind farms are located store three times as much carbon as a tropical rain forest.

According to University of East London scientist Richard Lindsay and his colleague Olivia Bragg, a construction-related accident involving two wind turbines near Galway, Ireland, released enough CO2 into the air to nullify any hydrocarbon reduction resulting from their use.

This is not to suggest that wind power is a bad idea. Most scientists warning of the need to study how turbines interact with the atmosphere - and with each other in different arrays - believe any problems can eventually be solved. "It's very clear to everybody that we have to move away from conventional fossil fuels," said Baidya Roy.

But he notes that people mistakenly "treat renewable energy as if it's a free lunch. ... That's not true. You always have to pay a price for any consumption."

Dismissing out-of-hand any proposal for a balanced energy policy - simply because it allows for both nuclear energy, which has the virtue that its waste can be contained, and the efficient use of hydrocarbons while we phase in greener power - makes no more sense than relying exclusively on oil, gas and coal.

Drilling for oil and natural gas may not be the environmentalist's nirvana, but it could be the least-worst energy alternative, if we use the time to harness renewable power with the same caution that many now apply to existing sources.

Lewis M. Andrews is the executive director of the Yankee Institute for Public Policy, P.O. Box 260660, Hartford 06126. E-mail: lew@yankeeinstitute.org.