Marco Rubio believes in market forces and would like to be seen as a high-minded leader dedicated to making sure the United States gets the big things right.

So after hearing him discuss issues important to young professionals on Wednesday at Saint Anselm College, I asked about a matter the world has to get right: climate change.

Specifically, would the Republican presidential hopeful support a tax on carbon to make the price of fossil fuels reflect their true climate-changing cost, thereby reducing their use and rendering clean-energy alternatives more competitive?

No, said Rubio.

"The proposals they keep presenting me with will do nothing," he said. "By the admission of the advocates, they would do nothing to change our environment. You can ask them, how many feet of sea rise will this prevent if we pass this bill, and their answer is, it won't prevent anything."


Really? I asked Princeton University climate expert Michael Oppenheimer, a lead author of the Intergovernmental Panel on Climate Change's latest report, about Rubio's claim that a carbon tax wouldn't be effective. (The IPCC is the most authoritative international body assessing climate change.) Assuming US adoption of a robust carbon tax led to commensurate carbon-reduction policies by other countries that are large emitters, the combined action could cut the projected rise in sea level by almost half by century's end, he said.

"It wouldn't matter much up until mid-century, then it starts to matter a great deal," he noted.

To assess the sea level effect, Oppenheimer compares the mid-range of the IPCC's business-as-usual and strong-action scenarios. By 2100, a significant carbon tax, with similar measures from other emitters, could mean the difference between a sea-level rise of about 17 inches and one of about 30 inches, he says. Given that more than 100 million people worldwide live within three feet of sea level, that matters. (On a typical US East Coast beach, each one-foot rise swallows about 100 feet of beach.)

To be sure, having other countries adopt a carbon tax (or the emissions-reduction policy equivalent) would require US leadership. But we're already seeing some promising movement. Prodded by the Obama administration, both China and India have now announced carbon-reduction targets. Problems remain, of course. China is using much more coal than previously thought; India's goals aren't considered strong enough. Still, both commitments are seen as setting the stage for progress at December's climate conference in Paris.


One way to promote broader adoption of a carbon tax, says Charles Komanoff, director of the Carbon Tax Center, would be for the United States and like-minded trading partners to impose a carbon tariff on goods from countries without such a tax or its policy equivalent.

"Then the countries that aren't taxing carbon would run to do it, because they would want to reap the revenues themselves rather than having their trading partners grab them through the tariff," he said.

Rising seas aren't the only climate-change concerns of course. Global warming also contributes to heat waves and drought, and intensifies storms, resulting in more violent weather.

Now, Rubio is hardly alone in his unwillingness to consider a carbon tax. Although Democrat Bernie Sanders supports such a tax, Hillary Clinton disappointed environmentalists by failing to embrace one as part of her anti-climate-change plan.

It's an important idea — far too important to be dismissed cavalierly, as Rubio did. He's either misinformed or, worse, trying to muddy the waters.

Scot Lehigh can be reached at lehigh@globe.com. Follow him on Twitter @GlobeScotLehigh.