PRESIDENT OBAMA hardly mentioned climate change during long stretches of his first term. As he rebuilds his administration and refines his second-term agenda, he should give this challenge the priority it deserves.

The biggest disappointment of Mr. Obama’s energy and environmental record was his failure to advance a bill that would have put a price on carbon dioxide emissions, which is the economically sensible way to cut them. Congress, too, bears blame for this, but the president allowed other priorities, such as health-care legislation and Wall Street reform, to gobble up his attention. By the time climate’s turn came, Washington was exhausted, and he could not even achieve a backup approach such as requiring that some of the country’s electricity come from clean sources.

Consequently the administration focused on what it could do without Congress. Here the record is brighter. Mr. Obama pushed through landmark fuel-efficiency standards for cars and trucks, an achievement that will reduce both oil use and the country’s carbon footprint. The Environmental Protection Agency (EPA) set air quality standards that all but guarantee that utilities won’t build any more hazardous coal-fired power plants.

The president also welcomed the revolution in domestic energy production that taps into vast deposits of natural gas, which burns cleaner than coal. The EPA and the Interior Department sided neither with environmentalists who want to shut down unconventional gas development nor with energy firms that would rather not see essential regulation.

Taken together, these efforts have helped put the country on a path toward reduced emissions, though it’s not as ambitious or as efficient a policy program as pricing carbon could have been.

In the next four years, there is more Mr. Obama can do administratively. His administration must ensure that natural gas production doesn’t result in excess greenhouse-gas pollution. The EPA can set carbon emissions standards on existing power plants and industrial sources, though regulators must be sensitive to compliance costs if they do so.

But the best policies to reduce the country’s emissions would require congressional action. Unfortunately, the president seems unwilling to push for a carbon tax or some other carbon-pricing policy during any tax reform negotiations. Given that a carbon tax could raise money and efficiently address greenhouse emissions, it seems like a perfect fit. Bipartisan coalitions could also unite around less controversial legislation that promotes energy efficiency and funds basic research into energy technology.

Straight talk is important. Policies to reduce emissions should not be justified with appeals to green jobs or energy independence. Americans should hear from their leaders about the risks the planet faces and why it makes sense to spend now to head off more costly consequences later.