Al Gore, never a favourite of the America’s conservative movement, has risked stoking further ire by comparing climate change deniers to racists, homophobes, smokers and drunks.

In an interview with the Washington Post’s Ezra Klein, the former Vice President, whose 2006 film An Inconvenient Truth was heralded by the left as much as it was admonished by the right, continued his campaign to bring climate change to the front of political debate ahead of publication of a UN report which cites human agency as the cause of rising temperatures.

al gore

Al Gore says climate change denial is melting away

Speaking to Klein, Gore compared his decade-long struggle to have climate change accepted to the Sixties battle over civil rights and the current debate over gay rights.

Well, I think the most important part of it is winning the conversation,” he said. “I remember as a boy when the conversation on civil rights was won in the South. I remember a time when one of my friends made a racist joke and another said, hey man, we don’t go for that anymore. The same thing happened on apartheid. The same thing happened on the nuclear arms race with the freeze movement. The same thing happened in an earlier era with abolition.

A few months ago, I saw an article about two gay men standing in line for pizza and some homophobe made an ugly comment about them holding hands and everyone else in line told them to shut up. We’re winning that conversation.

Gore added: "It’s like a family with an alcoholic father who flies into a rage every time a subject is mentioned and so everybody avoids the elephant in the room to keep the peace."

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As such, the former VP said that he was optimistic that the message was getting across and that the U.S. and the world was reaching a "tipping point" on climate change, driven by business and grass roots. "Policies and changes in law in places like india and China and Mexico and California and Ireland will proliferate and increase, and soon we’ll get to the point where national laws will evolve into global cooperation," he said.