WASHINGTON (AP) — Appealing for courageous action "before it's too late," President Barack Obama launched a major second-term drive Tuesday to combat climate change and secure a safer planet, bypassing Congress as he sought to set a cornerstone of his legacy.

Abandoning his suit jacket under a sweltering sun at Georgetown University, Obama issued a dire warning about the environment: Temperatures are rising, sea level is climbing, the Arctic ice is melting and the world is doing far too little to stop it. Obama said the price for inaction includes lost lives and homes and hundreds of billions of dollars.

"As a president, as a father and as an American, I'm here to say we need to act," Obama said. "I refuse to condemn your generation and future generations to a planet that's beyond fixing."

At the core of Obama's plan are new controls on new and existing power plants that emit carbon dioxide — heat-trapping gases blamed for global warming. The program also will boost renewable energy production on federal lands, increase efficiency standards and prepare communities to deal with higher temperatures. Obama called for the U.S. to be a global leader in the search for solutions.

But Obama's campaign will face extensive obstacles, including a complicated, lengthy process of implementation and the likelihood that the limits on power plants will be challenged in court. Likewise, the instantaneous political opposition that met his plan made clear the difficulty the president will face in seeking broad support.

"There will be legal challenges. No question about that," former EPA Administrator Christie Whitman said in an interview. "It's a program that's largely executive. He doesn't need Congress. What that does, of course, is make them (Congress) madder."

Obama also offered a rare insight into his deliberations on whether to approve the Keystone XL oil pipeline, deeming it in America's interests only if it doesn't worsen carbon pollution. Obama has faced intense political pressure from supporters and opponents of the 1,200-mile pipeline from Canada to Texas.

Declaring the scientific debate over climate change and its causes obsolete, Obama mocked those who deny that humans are contributing to the warming of the planet.

"We don't have time for a meeting of the flat-earth society," Obama said.

Obama's announcement followed years of inaction by Congress to combat climate change. A first-term effort by Obama to use a market-based approach called cap-and-trade to lower emissions failed, and in February a newly re-elected Obama issued lawmakers an ultimatum in his State of the Union: "If Congress won't act soon to protect future generations, I will."

Four months later, impatient environmental activists reveled in the news that Obama was finally taking matters into his own hands, announcing a series of steps that don't require congressional approval.

"This is the change we have been waiting for," said Michael Brune, who runs the Sierra Club, an environmental group. "Today, President Obama has shown he is keeping his word to future generations."

Republicans on both sides of the Capitol dubbed Obama's plan a continuation of his "war on coal" and "war on jobs." The National Association of Manufacturers claimed Obama's proposals would drive up costs. Republican Rep. Shelley Moore Capito of the coal-heavy state of West Virginia slammed what she called Obama's "tyrannical efforts to bankrupt the coal industry."

"The federal government should leave us the hell alone," said Texas Land Commissioner Jerry Patterson, whose agency handles Texas' environment and energy markets.

Even industry groups that have been friendly to Obama and supportive of his climate goals, such as the Edison Electric Institute, which represents power plants, signaled their apprehension by calling for "achievable compliance limits and deadlines."

Obama said the same arguments have been used in the past when the U.S. has taken other steps to protect the environment.

"That's what they said every time," Obama said. "And every time, they've been wrong."

Obama broke his relative silence on Keystone XL, explicitly linking the project to global warming for the first time in a clear overture to environmental activists who want the pipeline nixed. The pipeline would carry carbon-intensive oil from Canadian tar sands to the Texas Gulf Coast refineries and has sparked an intense partisan fight.

"Our national interest would be served only if this project does not significantly exacerbate the problem of carbon pollution," Obama said.

The White House indicated Obama was referring to overall, net emissions that take into account what would happen under alternative scenarios. A State Department report this year said other methods to transport the oil — like shipping it on trains — could yield even higher emissions.

"The standard the president set today should lead to speedy approval of the Keystone pipeline," said Brendan Buck, a spokesman for House Speaker John Boehner, R-Ohio.

Announcing he will allow more renewable energy projects on public lands, Obama set a goal to power the equivalent of 6 million homes by 2020 from sources like wind and solar, effectively doubling the current capacity. The set of actions also includes a new set of fuel efficiency standards for heavy-duty trucks, more aggressive efficiency targets for buildings and appliances, and $8 billion in federal loan guarantees to spur innovation.

By far the most sweeping element — and the one likely to cause the most consternation — is new limits on carbon dioxide pollution from power plants.

The administration has already proposed rules for new coal-fired plants, but they have been delayed amid industry concerns about the cost. A presidential memorandum Obama issued Tuesday directs the EPA to revise and reissue the new plant rules by September, then finalize them "in a timely fashion."

The key prize for environmental groups comes in Obama's instruction that the EPA propose rules for the nation's existing plants by June 2014, then finalize them by June 2015 and implement them by June 2016 — just as the presidential campaign to replace Obama will be in full swing.

Rather than issue a specific, uniform standard that plants must meet, the EPA will work with states, power sector leaders and other parties to develop plans that meet the needs of individual states and also achieve the objective of reducing emissions.