Comedian Bill Maher returned to HBO with Real Time with Bill Maher on Friday night and interviewed former Vice President Al Gore about the environment.

Maher pointed out that Gore, though he had been the butt of many a Republican joke, was right about climate change very early on.

“You were ahead on so many things, not just climate change, which is the issue of our time and you are the leading voice,” Maher said.

Gore said he hoped that the climate summit in Paris last year was a turning point, and said that the cost of producing solar power has come down enough so that it’s cheaper than burning coal.

“The more we expand solar energy, the faster the price comes down,” Gore said. “We’re very close to the point where it’s not going to be economical to burn fossil fuels for electricity any more. Wind is also coming down in cost.”

Maher then pointed out that the United States is alone in the world by having a major political party that calls climate change a hoax.

“The reason that is, is because we’re the most religious country of the modern countries,” Maher said. “And religious people don’t think global warming is a problem. They think the world is going to end.”

Gore disagreed and pointed out that Pope Francis has made an agenda out of addressing climate change.

Watch the exchange, as posted to YouTube, here: