WASHINGTON—For many young voters, the environment is a hot-button issue in this year’s presidential election. But some think concern over global warming is overblown.

Self-proclaimed global warming skeptic Roy Spencer, a former NASA scientist, drew applause Wednesday at the conservative Young America’s Foundation conference when he said the hype around the “green” movement is nearing the level of “a state-supported religion.”

Spencer, a climate researcher at the University of Alabama-Huntsville, said that although global warming is occurring, it’s not happening to the extent that many scientists have led the public to believe. Rising global temperatures will not have a significant negative impact on the planet, he said, because most warming has been the result of natural temperature fluctuations, not human causes like increasing carbon dioxide emissions.

“The climate system is relatively insensitive,” Spencer said. “That means that the CO2 we put in the atmosphere really doesn’t do much, maybe only one-tenth or two-tenths of a degree Celsius, which is basically trivial. Climate is going to change anyway, with or without us, so if we cause a little bit of climate change, so what?”

Nearly half of Americans believe that humans are the primary cause of global warming, although just 27 percent of Republicans share this belief, according to a Pew Research study released in May. About 58 percent of Democrats and 50 percent of Independents think human actions have caused global warming.

After the speech, Kendal Volz, 20, said he agreed with Spencer.

“I already kind of thought that global warming was based a bit more on natural factors so it was good to see someone with scientific information,” said Volz, of San Antonio, Texas. “Most of the news that we’ve been seeing is a bit biased so it was good to hear a different perspective.”

Taylor DuJack, 19, of Albany, N.Y., was more on the fence about the speech.

“It certainly didn’t dissuade me from the idea that global warming can be partially blamed on natural causes, but I really think it’s more of a mix of the two,” DuJack said. “I think that humans certainly do have some effect, but maybe it’s a little overhyped by the media and especially politicians.”

Just 16 percent of 18- to 29-year-olds say the presidential candidates are spending too much time talking about global warming, according to a CBS News/MTV poll released in April. About 47 percent think the candidates are not talking enough about to the issue, and 35 percent say it’s receiving the right amount of attention.