By Deborah Zabarenko, Environment Correspondent
WASHINGTON (Reuters) - For Al Gore, the choice is obvious: Either accept scientific reality about climate change or believe what the fossil fuel industry is paying some Republican candidates to say.
"Anti-climate lobbyists ... give massive campaign contributions and they're not shy about making it clear to the candidates they support that there's a quid pro quo. In return for getting their money, these candidates have to pretend that they really believe this nonsense," the longtime climate change campaigner said on Wednesday in a telephone interview.
Asked whether Republican candidates who have accepted contributions from fossil fuel industries are compelled to toe the skeptical line on climate change, Gore replied: "That is absolutely the case."
Gore -- a Nobel peace laureate, former vice president and star of the Oscar-winning documentary "An Inconvenient Truth" -- said "too many" in his own Democratic Party have done this too but did not name them.
"We have to weigh whether or not we will accept the judgment of every national academy of science of every major country ... or whether we'll instead take the advice of ExxonMobil and the Koch brothers and Rush Limbaugh and Glenn Beck," Gore said.
He cited the petroleum giant, the two chiefs of Kansas-based energy conglomerate Koch Industries and two conservative talk-show hosts.
REPUBLICANS CALL IT A "HOAX"
Most Republican presidential candidates, with the exception of Jon Huntsman, are skeptical about climate change science. Current front-runner Rick Perry has called the science supporting human influence on global warming "one contrived phony mess," while Michele Bachmann has called it a hoax.
Gore blamed these attitudes on the undue sway of the coal and oil industries in U.S. politics.
"The single largest source of campaign financing for most of those (Republican) candidates is the oil industry and the coal industry," he said. "And the oil companies in particular, starting almost 20 years ago, began a massive disinformation campaign" aiming to create doubt that human activities, including the burning of fossil fuels, spur climate change.
Climate skeptics often argue that natural variability is the main cause of changing change, and accuse some climate scientists of manipulating data, pointing to the so-called "Climategate" case involving hacked emails between climate scientists. Independent inquiries have found no wrong-doing by the scientists.
CLIMATE SKEPTICS' "ORTHODOXY"
"This is now to the point where anyone who is prominent in the Republican Party who has the temerity to assert the reality of the science is considered foolish politically for straying from this orthodoxy," Gore said.
He said this year's violent and expensive U.S. weather should be enough to convince anyone. But in case it is not, he is launching a new campaign called The Climate Reality Project, kicking off with "24 Hours of Reality" to be presented in 13 languages and a presentation for each time zone.
Visible online at http://climaterealityproject.org, the venture is to start at 8 p.m. EDT (0001 GMT) Wednesday with streaming video each hour from different locations, from New York and London to Tonga and Beijing. The first presentation is set to come from Mexico City.
Gore said he has no doubt that massive floods in Pakistan, Australia and along the Mississippi River, heat waves and droughts in Russia and Texas, and other severe weather events are related to human-influenced climate change.
"The deniers claim that it's some kind of hoax and that the global scientific community is lying to people," he said. "It's not a hoax, it's high school physics."
In a reference to the Tea Party movement and other U.S. conservatives who favor anti-tax crusader Grover Norquist's notion of shrinking the federal government "to the size where we can drown it in the bathtub," Gore warned of the consequences of accepting "alternative to reality pushed by carbon polluters and their ideological allies in the drown-the-government-in-the-bathtub crowd."
AN HONOR TO BE ATTACKED
But he said not all mainstream Republicans are doubtful about climate change and noted a long bipartisan tradition of environmental protection, from Teddy Roosevelt to Richard Nixon.
Gore said the difference now is the amount of money required to run a U.S. political campaign, as well as the global nature of climate change.
Gore acknowledges that he is often the public figure climate skeptics love to attack.
"That's an honor because there's a long tradition of people who hate a particular message choosing to attack anyone who serves as a messenger delivering that message. And I don't take that personally."
(Editing by Cynthia Osterman)