Houston-based ConocoPhillips has committed $2 million over two years to a group promoting a carbon tax.

ConocoPhillips, after Exxon Mobil, is the second oil and gas giant to give money to Americans for Carbon Dividends, an advocacy organization that lobbies Congress to support a carbon tax-and-dividend plan proposed by the Climate Leadership Council, a group led by two former Republican secretaries of state, James Baker III and George Shultz.

ConocoPhillips is also formally joining the Climate Leadership Council, the Washington Examiner has confirmed, after being a holdout. Other members include Exxon Mobil, BP, and Shell. Axios first reported the news.

“We are delighted to welcome ConocoPhillips into Americans for Carbon Dividends and commend their leadership in supporting this important initiative,” Former Senate Majority Leader Trent Lott, a Republican co-chair of Americans for Carbon Dividends, told the Washington Examiner. “The mounting financial support from companies most impacted by carbon policies sends a clear message to members of Congress that corporate America is serious about addressing this issue.”

The move by ConocoPhillips shows that oil and gas companies are not just rhetorically supporting carbon pricing proposals, but also dedicating money to lobby for them.

“We are pleased to now join the CLC to continue the dialogue around carbon price policy development in the United States,” said ConocoPhillips CEO Ryan Lance.

The Intergovernmental Panel on Climate Change, a panel of scientists convened by the United Nations, warned in a recent report that putting a high price on carbon is crucial for preventing the worst impacts of climate change as soon as 2040.

The Climate Leadership Council proposal would impose a carbon tax beginning at $40 per ton, and give the proceeds to the public through rebates, while scrapping carbon regulations imposed by the EPA.

It would also protect oil and gas companies from lawsuits by states and cities blaming them for climate change.

The plan would raise the cost of natural gas and coal, and likely, gasoline prices and energy rates, although backers claim that it would allow for rebate checks to consumers to more than offset the financial hit.

A coalition of House members recently introduced the first bipartisan carbon tax legislation in nearly a decade, with a plan that is broadly similar to the proposal that ConocoPhillips is now backing.

That bill would impose a tax of $15 per ton of carbon dioxide in 2019, increasing $10 each year, rising to nearly $100 per ton by 2030.

It distributes all of the proceeds from the tax into equal portions in the form of a monthly rebate to American households.

But ConocoPhillips is among the oil and gas giants that spent heavily to help defeat a carbon tax ballot initiative in Washington state this November. That proposal, however, planned to use the revenue differently, dedicating it primarily to funding clean energy projects.