WASHINGTON -- The Republican presidential candidates' answers to a climate change question during their Wednesday debate represented progress -- sort of.Florida Sen. Marco Rubio, who hadpreviously said he didn't believe humans are causing climate change, now sayshe's not a skeptic. Rubio, a Catholic, has softened his stance somewhat since the pope's encyclical on the environment. During the debate, he focused his remarks on his dislike of the Obama administration's regulatory measures and argued that U.S. efforts to reduce emissions would do little to curb climate change because "America is not a planet."New Jersey Gov. Chris Christie argued there doesn't need to be a "massive government intervention to deal with the problem" of climate change. He also set up and knocked down a straw-man argument that there is "some wild left-wing idea that somehow, us by ourselves is going to fix this problem."Wisconsin Gov. Scott Walker took a similar approach, arguing that the administration's new climate rules would destroy the economy but "will have a marginal impact on climate change."The other eight candidates on the main debate were spared from having to respond to the question -- which is probably good for Donald Trump, who apparently bases his climate change positionon audience surveys.Sure, what Rubio, Christie and Walker offered are still problematic talking points. There's no "left-wing idea" that the U.S. should act alone. In fact, the U.S. is only now participating in an international effort to curb carbon emissions, an effort that Republican leaders have beenworking hard to undermine. And of course the U.S. acting alone would have only a marginal impact on climate change -- that's the whole point of working toward an international agreement.But the three candidates' statements on climate change do represent some modest degree of progress -- in words, if not in substance. They reflect movement along the continuum of climate change denial, a five-step process that environmental scientist Dana Nuccitelli elegantly described in The Guardian several years ago. The stages:Deny there's even a problem at all.Deny humans are the cause.Deny that it will be that bad.Deny that humans can solve the problem.Argue that it's too late to do anything about it.I would amend that progression slightly, particularly in the American political context. Between steps 3 and 4, deniers here have added two more -- the "I'm not a scientist" step and the "it's too expensive to do anything about it" step.In 2014, the bulk of the Republican lawmakers appearedstuck in the "not a scientist" stage. The phrase was uttered so many times that it became a punch line for President Barack Obama. It is a creative turn of phrase, since it allows one to both evade stating an opinion about whether climate change is happening or what the cause may be, and also avoid stating whether it's a serious concern worthy of government action.This year, however, Republican presidential candidates seem to be moving ever so slowly into the next phase, somewhere between "it's too expensive" and "even if we did something, it wouldn't matter anyway."The good news about those two stages is that they're relatively easy to counter with arguments that have nothing to do with one's understanding of science. The costs of not acting on climate change are mounting, as is the evidence that doing nothing is the most expensive option. Earlier this year, the Environmental Protection Agency projected costs of climate changefor various aspects of the U.S. economy this century, including $7.4 billion for road maintenance and repairs and $3.1 billion due to rising sea levels and storm surges. But you don't have to listen to the hippies at the EPA. You can listen to a bunch of business leaders, economists and advisers to Ronald Reagan, or to the leaders of 13 of the world's largest energy companies, or to a group of House Republicans.So, too, is the impetus for world action increasing. China has agreed tobegin cutting emissions in the near future, and is working collaboratively with U.S. partners on local efforts. More than 60 other countries haveput forward their own individual pledges on greenhouse gases. The notion that the U.S. would be going it alone has never really been valid, but now it's even less so.The 2016 GOP contenders may still be a long way from advancing real solutions to the climate crisis. But at least the candidates who discussed it on Wednesday shed the most tired of all excuses for not acting: ignorance of the problem itself. -- This feed and its contents are the property of The Huffington Post, and use is subject to our terms. It may be used for personal consumption, but may not be distributed on a website. Click here to read full news..