President Barack Obama challenged America and the world to step up efforts to fight global warming on Monday at the formal unveiling of his administration’s controversial, ramped-up plan to cut carbon emissions from U.S. power plants.

Declaring climate change the greatest threat facing the world, Obama said the regulation requiring the power sector to cut its emissions by 32 percent from 2005 levels by 2030 would reduce Americans’ energy bills and improve the health of vulnerable populations nationwide.

The plan, which also mandates a shift to renewable energy from coal-fired electricity, is meant to put the United States in a strong position at international talks in Paris later this year on reaching a deal to curb global warming.

The United States has pledged to slash its greenhouse gas emissions across the economy by 26 to 28 percent below 2005 levels by 2025. Cuts from the high-emitting power sector will be critical to the effort, and the White House hopes this plan will prove Washington’s commitment to that goal as it prods other countries to follow suit.

Obama is enacting the plan by executive order, bypassing Congress, which rejected legislative attempts to reduce pollution from carbon dioxide, a common greenhouse gas blamed by scientists for heating the earth.

The regulations face certain legal challenges from states and industries, and their long-term fate depends on their ability to withstand such challenges.

“We’re the first generation to feel the impact of climate change. We’re the last generation that can do something about it,” Obama told a sympathetic audience at the White House.

“We only get one home. We only get one planet. There’s no plan B.”

The Clean Power Plan is intended to be a key part of the president’s legacy on global warming, which he pledged to fight as a candidate for the White House in 2008.

The effort also sets up climate change as a political lightning rod in the 2016 presidential election.

Former Secretary of State Hillary Clinton, the front-runner for the Democratic nomination, said she would defend the plan while Jeb Bush, one of a slew of Republicans running for their party’s nomination, said it would cost people jobs.

“EXPENSIVE, ARROGANT”

Other leading Republicans also stressed what they said were the costs to the economy from the plan.

Senate Majority Leader Mitch McConnell said the new rules would shutter power plants and drive up electricity costs.

“I will do everything I can to stop it,” he said.

The Republican Speaker of the House of Representatives, John Boehner, called the plan an “energy tax.”

“I believe this final plan is an expensive, arrogant insult to Americans who are struggling to make ends meet,” he said.

Obama rejected criticism that his plan would increase energy bills for Americans and hurt the poor, saying, “If you care about low-income, minority communities, start protecting the air that they breathe.”

The re-vamped Clean Power Plan gave a boost to renewable energy, which would account for 28 percent of the U.S. energy mix by 2030 from just under 10 percent currently if enacted.

Jeff Holmstead, a partner at Bracewell & Giuliani and a former official at the Environmental Protection Agency, said the bigger role for clean energy such a solar and wind was meant to impress allies in the Paris talks.

“The EPA did a little bit of puffery to make the U.S. commitment look even bolder before Paris and they (allies) should be wary of the U.S. plan,” he said. “Europeans especially know too well that overreliance on intermittent energy sources can create its own economic hardships.”