During his run for the White House, Barack Obama pledged to transform the way Americans produce and consume energy. Such promises come cheap on the campaign trail. In the real world they cost money and political capital.

Recently, in his speech to Congress, Mr.Obama made clear that he is ready to spend both to combat climate change and reduce America’s dependence on fossil fuels.

Obviously, a lot of very heavy lifting lies ahead. The president must persuade everyone from Congress to American taxpayers to the Chinese leadership to follow. We applaud his vision and urge him to push forward.

Mr.Obama listed energy, along with health care and education, as critical to the nation’s economic future. He urged Congress to send him legislation that would place a mandatory and steadily declining cap on carbon emissions from power plants and other sources. This would require emitters to invest in more efficient plants and cleaner fuels and, at least initially, is likely to lead to higher energy prices.

It was impossible to listen to him without drawing contrasts to the early Bush days - to former President George W.Bush’s swift renunciation of his campaign promise to regulate carbon dioxide and his easy and unsubstantiated assumption that fighting climate change could only damage the American economy.

Mr.Obama’s commitment has been more than rhetorical. Five weeks into his presidency, he has signaled a readiness to regulate greenhouse gases from cars, trucks and new power plants, to require more fuel efficient vehicles and to invest heavily in energy efficiency - including high speed rail and weatherizing homes - as well as renewable energy sources like wind and solar.

Nearly one-tenth of his economic recovery package, $80 billion altogether, is devoted to these purposes.

Not surprisingly, given the state of the American economy, his speech dwelled less on the perils of climate change and more on the economic promises of clean energy.

He spoke of the profit to be gained by American industries and workers if the United States took the lead in investing in manufacturing wind turbines, more efficient solar panels and next-generation batteries - reminding his audience that on these fronts China, Germany and Japan are doing better than we are.

This was smart. Emphasizing the economic potential of a program that will carry a substantial price tag is surely one good way of selling it.

There also are extraordinarily thorny questions of design. Congress’s last effort produced a bill of nightmarish complexity. To get one through this year or even next will require all of Mr.Obama’s persuasive skills.

Merely acknowledging a problem is not the same as addressing it. It has been four decades since Richard Nixon urged Congress to free the nation from its dependence on foreign oil, and the country is more dependent than ever. It has been well over a decade since the world’s industrialized nations agreed in Kyoto, Japan, to control global-warming emissions, and emissions continue to rise. Mr.Obama is challenging not just the country, but history.