By Alister Doyle
OSLO (Reuters) - Americans are likely to have six times more days above 35 degrees Celsius (95 Fahrenheit) by 2100, partly because of climate change, scientists said on Monday, with heat already linked to hundreds of deaths a year in the United States.
By the late 21st century, exposure to sweltering heat would leap to between 10 and 14 billion "person days" a year, a team led by Bryan Jones of the Baruch College School of Public Affairs in New York wrote in the journal Nature Climate Change.
There were 2.3 billion such days of extreme heat in the United States in the late 20th century in a typical year, based on the population in places with daily highs above 35C, multiplied by the number of days as hot as that or hotter.
The study was based on a U.S. population of 470 million by 2100, up from about 280 million in 2000.
U.N. studies say man-made greenhouse gas emissions from burning fossil fuels are pushing global temperatures higher.
"Both climate and population change are significant contributors to this potential increase," the study said.
Another report in Nature Climate Change on Monday found that warming could curb electricity generation in the western United States by reducing water at hydro-electric dams or the amount of cooling water available for coal or nuclear power plants.
"At present, power providers do not account for climate impacts in their development plans, meaning that they could be overestimating their ability to meet future electricity needs," according to the study by Arizona State University.
Nearly half the west's summertime generation capacity could be reduced by between 1.1 and 3.0 percent by 2050, it said.
(Editing by Louise Ireland)