Sen. Marco Rubio (R-Fla.). (Carlo Allegri/Reuters)

Like many GOP presidential hopefuls, Sen. Marco Rubio (R-Fla.) is trying to locate the maximally spineless position on climate change, bending to the anti-scientist crowd without sounding wholly anti-science. And like many GOP presidential hopefuls, he looks not just cowardly but intellectually hollow. Here’s his latest attempt, on Sunday’s Face the Nation:

Humans are not responsible for climate change in the way some of these people out there are trying to make us believe, for the following reason: I believe the climate is changing because there’s never been a moment where the climate is not changing. The question is, what percentage of that … is due to human activity? If we do the things they want us to do, cap-and-trade, you name it, how much will that change the pace of climate change versus how much will that cost to our economy? Scientists can’t tell us what impact it would have on reversing these changes, but I can tell you with certainty, it would have a devastating impact on our economy.

Rubio seems to be mashing up three climate-doubter themes: He attacks scientists, he attacks the cost of emissions-reductions policies and he attacks the notion that anything the United States does about climate change will matter. But most important, he keeps it all really vague. He opposes some unspecified policies favored by unspecified “people” because of an unspecified amount of skepticism about the science. He seems to admit that humans have some role in driving climate change, not as much as “some” claim, but he doesn’t say how much. And he fails to articulate what policies he does favor.

This formless mess fails to stand up to even modest amounts of scrutiny.

Rubio’s suggestion that “some” people — scientists? policymakers? underpants gnomes? — are “trying to make” us worry more than we should allows him to play to climate-science-is-a-hoax conspiracy theorists without explicitly endorsing their wackiness. But it also emphasizes the fact that Rubio hasn’t explained what the proper degree of alarm is — and, from there, what to do about it.

Perhaps, somehow, all Rubio thinks is that “some people out there” are too alarmist, and that acting effectively on emissions would be expensive and difficult, so we shouldn’t bother with ambitious policy. By emphasizing the costs of acting on climate change without admitting that there is a benefit to hedging against the risk of bad climate outcomes, this line of attack encourages people to feel comfortable putting short-term economic concerns far ahead of long-term environmental ones. But this argument rests on the notion that government shouldn’t hedge against risks to society, which are by their nature uncertain, because hedging costs some money up-front. This is not credible.

Rubio also seems to echo concerns that if the United States acts alone, other nations will just keep on polluting, drowning out any speculated climate benefit. Ignoring the fact that the United States is not acting alone.

By offering no alternative emissions plan, meanwhile, Rubio remains strategically evasive. And he also fails a basic test of leadership.

Unfortunately, none of this makes Rubio much different from many of those in his party at the moment. A lot of good things are happening on emissions policy now. It will be crucial to determine not just that the eventual GOP nominee opposes Obama administration policies, but what he would do to change them — and whether his position disqualifies him from leading the country.