Over the final days of the campaign, CJR is running a series of pieces under the headline “Ask Obama This” and “Ask Romney This,” suggesting themes and questions that reporters and pundits can put to the presidential candidates. Previous installments have posed questions about a short-term plan for the jobs crisis; about housing; and about the Middle East, China, and Africa.

At the third and final presidential debate on Monday night, moderator Bob Schieffer of CBS News passed up what was probably the media’s last chance on a big stage to ask the candidates what they’d do, domestically and internationally, about climate change.

We know a fair amount about Barack Obama and Mitt Romney’s views on a related issue—energy policy—that they’ve made a central part of their campaigns. Each man supports an “all of the above” plan, but that shared rhetoric belies important differences in the subtle ways that Obama tilts toward renewables while Romney tilts toward fossil fuels. Even within this area there are many unanswered questions, of course. Both men support developing more nuclear power, for instance, but neither has talked enough about the serious economic and technical hurdles facing the industry. Still, voters have had a chance to learn about the distinctions between Obama and Romney on this front.

But the candidates have kept their exchanges about energy policy entirely within the frame of economic growth and job creation—avoiding almost any discussion of the general environmental and public health consequences of their respective platforms, and talk of climate change in particular.

Back in April, Obama told Rolling Stone that he was going to “very clear” about the need to take “take further steps to deal with climate change,” and Romney disavowed any intention to address the phenomenon during the Republican primary. But since then, there’s been next to nothing. In early September, the candidates responded to a set of questions from the group ScienceDebate.org, including one about climate change. Romney threw in some skeptical words about the science, yet both he and Obama said they want to reduce greenhouse gas emissions—the president through a combination of regulation and investment in clean-energy technology, and Romney through an embrace of nuclear power and a focus on economic growth.

Unfortunately, that’s about as far as either candidate has been willing to go to explain his strategy. Neither Obama nor Romney “mentioned the words climate change or global warming during three presidential debates that spanned more than four hours. And their running mates ignored the issue too,” Politico’s Andrew Restuccia reported on Tuesday, in a piece that quoted a ClimateSilence.org representative noting that this is the first time climate change has gone unacknowledged in the debates since 1984.

As Suzanne Goldenberg, who covers the environment for The Guardian, put it in the lede of her story Tuesday:

The Pentagon ranks it as a national security threat and, left unchecked, climate change is expected to cost the US economy billions of dollars every year—and yet it has proved the great unmentionable of this election campaign.

The candidates’ speechlessness is unconscionable. Romney needs to explain how the free market, left to its own devices, would ever lead to the kind of reductions in greenhouse gas emissions that are called for. And now that the Environmental Protection Agency has proposed the first-ever carbon pollution standards for new power plants and introduced strict new fuel-efficiency standards for vehicles, Obama needs to explain what, if anything, he’ll do to help get international efforts to address climate change back on track.

Curtis Brainard is the editor of The Observatory, CJR's online critique of science and environment reporting. Follow him on Twitter @cbrainard.