On Wednesday, Senators Jeff Flake (R-Ariz.) and Chris Coons (D-Del.) introduced a Senate bill to impose a carbon tax on major industrial carbon emitters throughout the US. The Senate bill is a version of a bipartisan House bill that was introduced in late November. Although most analysis agrees that the bills don't stand a chance of becoming law, they are important as concrete examples of avenues that US lawmakers are taking to explore bipartisan climate-change policy.

Traditionally, Republicans have resisted addressing climate change in any way whatsoever, with current Republican President Donald Trump baselessly calling climate science into question and hiring agency secretaries advisors , and administrators who repeat similar empty claims. But some Republicans in the House and the Senate have pushed back on this, especially in Florida where sea-level rise and increasingly violent hurricanes threaten the economy more directly than in other parts of the US.

The carbon-tax idea was re-introduced this year by Florida's Republican Representative Carlos Curbelo. (Curbelo lost his seat to a Democrat in the midterm election this year.) The idea of a carbon tax is attractive to many Republicans because it discourages carbon emissions via a market mechanism and protects big companies like Exxon from other kinds of government intervention. A carbon tax is a predictable, monetary lever with uniform increases over several decades; in other words, it's easy for companies to plan for in their balance sheets.

Big oil companies, like Exxon Mobil and ConocoPhilips, have started spending lobbying money in favor of a carbon-tax plan. They assume that complying with a carbon tax will be less onerous than complying with more aggressive climate policy in the future.

Republicans also want to keep a carbon tax "revenue-neutral" by distributing the proceeds of the tax back to Americans in the form of a monthly rebate rather than have the federal government use the revenue to subsidize other kinds of environmental programs.

Like the recently introduced House bill, the Senate bill would charge companies $15 per ton of carbon emitted and increase that fee by $10 per year. As a result, "the legislation would aim to reduce greenhouse gas emissions by 40 percent within 10 years and 91 percent by 2050," The Hill writes.

The Senate version of the bill has more protections in place to make sure that US emissions are indeed following that predicted trajectory—it specifies that the Environmental Protection Agency (EPA) can step in at any time to regulate greenhouse gas emissions if the tax isn't working well enough.

The House bill, by contrast, prohibits the EPA from stepping in unless the tax is ineffective after a decade.

With this year's Congressional session coming to a close, the Senate bill probably won't go far, but it does mark a potential starting point for bipartisan Congressional action next year.