Nuclear and coal-fired electrical plants are vulnerable to climate change, U.S. researchers say, as water used to cool their turbines is becoming too warm. Several thermoelectric power plants in the United States and Europe have had to operate at reduced electricity production or even be shut down temporarily because of warmer water and reduced river flows, the University of Washington reported Sunday. For instance, researchers said, the Browns Ferry Nuclear Plant in Alabama was shut down more than once last summer because the Tennessee River\'s water was too warm to use for cooling. Thermoelectric plants using nuclear or fossil fuels to heat water into steam to turn turbines supply more than 90 percent of U.S. electricity and three-quarters of European electricity. They require consistent volumes of cooling water at a particular temperature to prevent the turbines from overheating, but increasing air temperatures associated with climate change leading to warmer water mean higher electricity costs and less reliability, researches said. \"This study suggests that our reliance on thermal cooling is something that we\'re going to have to revisit,\" said researcher Dennis Lettenmaier, a UW professor of civil and environmental engineering.