This is Climate One, changing the conversation about America's energy, economy, and environment.

I'm Greg Dalton.

For 20 years, Jerry Taylor ran the energy and climate programs for conservative organizations funded by the Koch brothers.

There's a long line of wolf crying that as a conservative caused me to downgrade a lot of what I was hearing out of the environmental community.

But now, Taylor has gone from climate denier to climate mainstreamer.

These things could all happen in our lifetimes or our children's lifetimes, but maybe they won't.

But the fact is, they are scenarios that are quite plausible.

Donald Trump once advocated for climate action. Now he's rolling back

Barack Obama's efforts in that direction, says former White House science advisor John Holdren.

Not just the ones about climate change, but initiatives around water pollution, around air pollution,

about land and ecosystem preservation. It's terrible. A climate convert and President Obama's carbon legacy.

Up next on Climate One.

I'm Greg Dalton and I host Climate One Conversations

with oil companies and environmentalists, Republicans and Democrats.

The Stimulus Act passed early in Barack Obama's presidency included $40 billion to move the country to cleaner and more efficient energy.

He also increased auto mileage standards for the first time in decades, but failed to get

Congress to pass a bill putting a price on carbon pollution. As Obama's White House science advisor

for both terms, John Holdren was a key provider of facts and data for the professor

turned president. In our recent conversation, Holdren looks back at Obama's record and weighs in on

what's happening now. I think the biggest damage that the Trump administration is doing is, first of all,

reducing or proposing to reduce very drastically investments in clean and efficient energy research

and development by the government. In this country, for a very long time, we've had a symbiosis

...