WASHINGTON - He has served under three presidents and advised some of the world's largest companies. And whether it was the 2000 presidential election recount or a conflict in western Africa, he has earned the reputation as a man to whom world leaders turn in a crisis.

But James Baker III, the former secretary of state who now sits atop the Houston law firm Baker Botts and its roster of oil and gas clients, found himself cast into a new role Wednesday as an improbable hero of the movement to stop climate change.

Baker, 86, traveled to Washington as part of a newly formed coalition that includes former Treasury Secretary Hank Paulson, former Secretary of State George Shultz and former Wal-Mart Chairman Rob Walton to press President Donald Trump to back a proposal that would place a tax on carbon emissions and then return that money to U.S. taxpayers through a dividend payment.

Waiting for his flight back to Houston on Wednesday after a meeting at the White House, Baker said Trump's National Economic Council director, Gary Cohn, didn't give an immediate response, but "I think they're going to look at it."

"If you're a Republican, there's a lot to like," Baker said. "The risks are so great if the greenies are right. You need an insurance policy, and this is a damn fine free market, conservative, less-regulation proposal. It's very simple, and it will work."

Baker's support for a carbon tax enlivens a longstanding policy debate that to date has failed to find much if any traction among elected officials from either party.

The idea espoused by many economists is that if a government is going to address climate change and reduce greenhouse gas emissions, the most cost-effective way to do so is not by putting caps on emissions, but by simply taxing them. Supporters of a carbon tax include former Vice President and climate advocate Al Gore, leading environmental groups and even some large oil companies, including Exxon Mobil Corp., BP and Royal Dutch Shell.

An Exxon Mobil spokesman said Wednesday the proposal "appears to be consistent with several of the principles of an effective carbon policy."

The proposal was outlined in an op-ed piece in the New York Times co-authored by Harvard economists Martin Feldstein, who was chairman of the White House Council of Economic Advisers under President Ronald Reagan, and N. Gregory Mankiw, who held the same post under President George W. Bush. The third co-author was Ted Halstead, founder and chief executive of the Climate Leadership Council, a Washington advocacy group promoting carbon taxes to address global warming.

But the concept of a new tax has long proved too high a hurdle, as politicians fret that rising prices at the gasoline pump and large heating bills would lead to a backlash from voters. At least among rank-and-file Republicans, an endorsement from Baker and Paulson - and a supportive tweet from former presidential candidate Mitt Romney - did not appear to change much Wednesday.

The conservative group Heritage Action lashed out in an email, calling the proposal "just the latest example of policy solutions crafted by and made for cultural elites."

"Notwithstanding the great respect I have for (Baker) and Secretary Shultz, I don't see any need for a carbon tax. I don't feel a popular uprising in Texas or around the country," Sen. John Cornyn, R-Texas, the majority whip, said Wednesday. "I guess we'll just have to agree to disagree on that."

Under the plan put forward Wednesday, the U.S. government would institute a $40-per-ton carbon tax that would increase over time. The tax revenue would be returned to taxpayers through a dividend estimated at $2,000 a year for an average family of four.

At the same time, a border tax on carbon would be implemented to "protect American competitiveness and punish free-riding by other nations." And much of the U.S. Environmental Protection Agency's carbon regulations - like the disputed Clean Power Plan - would be terminated.

Enacting a carbon tax would bring the United States in line with a growing list of countries that regulate carbon. China has announced it will put into place a cap-and-trade scheme this year, in which companies that produce fewer carbon emissions can sell credits to those that exceed the cap, providing economic incentives to pollute less.

The proposal would also put the United States on track to meet the goals former President Barack Obama agreed to in the Paris climate change conference in 2015, said Noah Kaufman, a climate economist with the environmental think tank World Resources Institute.

"It's incredibly promising, the proposal itself and the fact that prominent, serious Republicans are doing the proposing," he said. "You don't know exactly how people would respond, but it looks like it would actually cause quite a bit more reductions than (Obama's) Clean Power Plan."

But if environmentalists are looking for a champion, they might well find themselves disappointed in Baker.

The former secretary of state still describes himself as a "climate change skeptic," though one who concedes the planet is warming and mankind is playing some role - how much is impossible to say, he says.

That puts him outside the overwhelming consensus of climate scientists, but his views are also considered anathema by many Republicans, who would just as soon see no action on climate change.

Trump himself has in the past called climate change a Chinese hoax and more recently questioned predictions by scientists of flooded coastlines, crop failures and water shortages.

Baker, who says he joined the coalition after being approached by Shultz more than a year ago, said he didn't expect Republican lawmakers to sign on immediately. Rather, he said, the proposal is a starting point to give the party "a seat at the climate change table."

"We'll see what happens," he said. "Is it an uphill climb? You bet it is. Is it something you that needs to be done? You bet it is."