THE ENVIRONMENTAL Protection Agency began marathon public hearings July 29 on its new climate-change plan. “This week,” the Natural Resources Defense Council’s Frances Beinecke predicted before the sessions, “we’ll hear loud and clear that the American people are strongly behind the EPA’s plans.”

Things were loud, anyway.

Industry groups, environmentalists and various other activists pushed alternate versions of reality. The EPA’s proposed greenhouse-gas program “threatens to dismantle our nation’s economy, fundamentally alter the American way of life and severely hamper U.S. energy independence and leadership,” according to Lauren Sheehan of the American Coalition for Clean Coal Electricity . Those on the other side of the debate argued that those sorts of things would happen without strong efforts to slash greenhouse emissions. Punctuating the point, the Moms Clean Air Task Force brought children to EPA headquarters to protest the spoiling of the planet for future generations.

In this ongoing back and forth, the Obama administration has tried to produce specific numbers to justify its plan. In June, the EPA calculated that the various benefits of its new anti-carbon rules — both in terms of fighting global warming and in terms of cleaner air — outstrip the inevitable costs many times over. On Tuesday, the Council of Economic Advisers released a separate analysis finding that each decade action on carbon emissions is delayed increases the cost of meeting carbon targets by 41 percent, and that acting in a timely manner is economically worthwhile even if some countries have not yet committed to cutting their emissions. Yet high levels of uncertainty about the economic consequences of unabated climate change, how energy technology will develop and other important factors make these estimates more general indications than precise outlines of the relevant economic considerations.

Still, general indications are enough. Here’s the reality: The world is warming, scientists say humans are responsible, the United States has contributed more than any other nation to the carbon dioxide that is already in the atmosphere, and the problem won’t get addressed any time soon without serious U.S. buy-in and leadership. The consequences of unabated warming are somewhat uncertain — yet the possibility of very negative, perhaps catastrophic, global outcomes is too distinct to do nothing.

Congress has failed to pass a plan tailored to cut U.S. greenhouse emissions over the next few decades. So the EPA has had to rely on the tools Congress gave it in the Clean Air Act to jury-rig a carbon-reduction system sufficiently ambitious to give the U.S. credibility to demand meaningful sacrifices from other nations. The agency has tried to use those tools to achieve notable U.S. carbon cuts without excessive cost. There are nevertheless much more efficient anti-greenhouse gas policies available, such as a simple economy-wide carbon tax. But the EPA’s critics oppose those, too, and the Obama administration can’t impose solutions without Congress’s approval.

Unless and until the EPA’s attackers get behind a real climate plan, the EPA has reason to fill Congress’s irresponsible policy void. The agency’s plan won’t destroy the American way of life. It will have some costs, but it will also get the country started on the emissions path it must sooner or later travel.