THE OBAMA administration has finally rolled out its centerpiece climate change policy. It is a praiseworthy, solid step, taken in the face of withering opposition. Even so, it is not enough.

Environmental Protection Agency Director Gina McCarthy released Monday a plan to slash greenhouse-gas emissions from existing power plants, which account for about 40 percent of the country’s carbon dioxide output. Instead of regulating plant by plant, the proposal sets emissions goals for the states and provides flexibility on how to meet them. States can push changes to power plants and the fuels they use, reduce electricity waste, promote renewable energy or all of the above. States can also band together into regional carbon-cutting pacts, which would offer even more flexibility to meet emissions goals at the lowest cost this sort of regulation could achieve.

By 2030, the plan would reduce electricity-sector emissions by 30 percent of 2005 levels, the EPA estimates, and it would benefit public health by improving ambient air quality. The agency also calculates that the benefits would outstrip the costs many times.

These numbers will be fought over — including by those who believe they do not fully represent the benefits. But the main point is that this plan is a down payment on a comprehensive climate plan, not the most efficient policy nor a suitably ambitious response to climate change. Assuming the proposal survives the inevitable legal onslaught, opponents will no doubt insist that the climate issue is dealt with. Global warming activists got their regulations, so why do any more?

A few reasons (there are many): The EPA’s new plan is a medium-term policy, but the country requires a long-run transformation in how it produces and consumes energy. Its implementation will depend heavily on who’s in the Oval Office; not much would happen in a Ted Cruz administration. The proposal applies only to the electricity sector, but emissions result from activities across the economy.

A simple, steadily rising carbon tax would address all of these drawbacks, accomplishing more at less expense. But President Obama had to do what he could under existing authorities. No matter how it came out, it would not have been the strong, efficient and comprehensive plan the country still needs.

There is one more shortcoming to the EPA’s plan, one that climate policy skeptics themselves frequently point out: It does not apply to the rest of the world. Without global effort, U.S. carbon cutting will not move the planet’s emissions needle nearly enough. But doing nothing is not an option. Sustained international engagement backed by serious and credible commitments — like the EPA’s latest plan — will be necessary. And countries such as China and India will not move if the United States does not move first.

The Obama administration’s job is not over. And Congress, so long negligent on climate, is not absolved of its responsibility to act.