“This is one of those rare issues, because of its magnitude, because of its scope, that if we don’t get it right, we may not be able to reverse,” he said, at the White House.

“We may not be able to adapt sufficiently.”

In an attempt to at least try to slow the process, Obama announced that power plant owners must cut carbon dioxide emissions by 32 percent from 2005 levels by 2030.

Electric power plants account for some 40 percent of U.S. emissions of carbon dioxide, the most common greenhouse gas that contributes to climate change.

Obama described the move as “the single most important step America has ever taken in the fight against global climate change.”

The announcement fires the starting gun on a months-long environmental drive that will shape his legacy.

Later this August, Obama will become the first president to visit the Alaskan Arctic.

“Our fellow Americans have already seen their communities devastated by melting ice and rising oceans,” Obama said.

In September, when Obama hosts Pope Francis at the White House, they are expected to make an impassioned collective call for action.

And in December, representatives from around the world will gather in Paris to hash out rules designed to limit global temperature increases to two degrees Celsius.

But Obama’s invocations got short shrift from the Republican-controlled Congress, which described the measures as “overreach” and “heavy-handed.”

In its initial proposal a year ago, the Obama administration had set the carbon emissions cut from the power sector at 30 percent.

Climate change is a hot-button issue in American politics and cuts are politically sensitive because coal, among the dirtiest energy sources, remains a major U.S. industry.

It has some influential supporters, including Senate Majority Leader Mitch McConnell, a senator from coal-rich Kentucky.

“Not only will these massive regulations fail to meaningfully affect the global climate, but they could actually end up harming the environment by outsourcing energy production to countries with poor environmental records like India and China,” said McConnell.

The leader of the House of Representatives Kevin McCarthy accused Obama of choosing a “green legacy over a growing economy.”

The American Coalition for Clean Coal Electricity, an industry lobby group, previewed likely legal action, saying Obama’s administration was “pursuing an illegal plan that will drive up electricity costs and put people out of work.”

Accusing detractors of “scaremongering,” Obama insisted that suggestions of higher electricity costs, power shortages and a damaged economy would prove incorrect.

“When president (Richard) Nixon decided to do something about the smog that was choking our cities, they warned that it would ruin the auto industry. It didn’t happen,” Obama said.

“In 1990, when Republican president George H W Bush decided to do something about acid rains, (they) said electricity bills would go up, lights would go off. It didn’t happen.”

“We only get one home. We only get one planet. There’s no ‘plan B’,” he said. (AFP)