Beware of oil companies bearing gifts. Recently, the lobbyists and former Senators Trent Lott and John Breaux, backed by companies like Exxon Mobil and Shell, have been campaigning for a federal tax on carbon dioxide emissions. This would increase energy costs, but all revenue from the tax would be returned to the public. A family of four might receive a $2,000 check from the government every year. And we would all have an incentive to reduce our use of carbon-based fossil fuels in favor of clean energy.

Most environmentalists, including us, desperately want a meaningful tax on carbon. But several of the people involved in this proposal have shown little previous interest in climate change. The oil industry had few better friends than Mr. Lott, a Republican from Mississippi, and Mr. Breaux, a Democrat from Louisiana, when they were in office. So what is going on here?

Well, Mr. Lott and Mr. Breaux aren’t simply proposing a tax, but a deal: a carbon tax in exchange for two other things. First, they want “an outright repeal of the Clean Power Plan,” which allows the Environmental Protection Agency to regulate carbon emissions and which the Trump administration is moving to cancel. Second — and most consequentially — they want to give fossil fuel companies immunity from lawsuits seeking to hold them accountable for damage they have done to the climate. As their proposal puts it, “Robust carbon taxes would also make possible an end to federal and state tort liability for emitters.”

Not coincidentally at all, 14 local and county governments and the State of Rhode Island filed such lawsuits in the last year, trying to make big oil companies pay their fair share for climate adaptations — the fortifications against the consequences, for instance, of rising seas, extreme weather and prolonged droughts. (The Rockefeller Family Fund has funded organizations that support the goals of these lawsuits.) Making the polluter pay is a bedrock environmental principle and a matter of simple justice. If the companies most responsible for climate change can escape liability, then ordinary citizens will have to shoulder the burden of adapting to the changing climate, which over the next few decades will cost this country trillions of dollars.