With airplanes flying over regularly, and sweat dripping from his brow, the president unveiled the most ambitious climate change plan in American history today in a speech at Georgetown University. The biggest unexpected news: among his proposals, detailed here, the president set a critical emissions measure for approval of the Keystone XL pipeline.

Obama's rhetoric was typically powerful. (Read the complete transcript.) "As a president, as a father, and as an American, I am here to say: We need to act." Less than 15 minutes into the speech, television news networks switched away from the speech, prior to Obama's full explication of his proposal. The Weather Channel, however, stuck with it.

Obama laid out the rationale for action: Climate science isn't new, dating to the period during which we first went into space. We began measuring carbon pollution, and watched as it climbed. "These are facts," the president stated flatly. And demonstrable ones. Obama noted the exceptional weather of 2012. The hottest year in history, the worst drought since the Dust Bowl, Hurricane Sandy. "In a world that's warmer than it used to be," he said, "all weather events are affected by a warming climate."

Those areas affected by climate change can't wait for action, he said. "The overwhelming judgment of science, of chemistry and physics … have put that to rest. The planet is warming, and human activity is contributing to it."

He outlined why the government had no choice but to act: under the Clean Air Act (which passed both chambers of Congress with only one "no" vote), the EPA is mandated to curtail carbon dioxide emissions because courts have ruled that the gas is a pollutant. (We've noted this before.) He had no choice, then, but to "put an end to the limitless dumping of carbon pollution from power plants." Coal companies and polluters would say that the proposal is a job-killer, Obama noted. How did he know? "Because that's what they say every time!" Those who thought that the economy couldn't adjust, he said, have "a fundamental lack of faith in American business and American ingenuity."

His proposals, as we reported earlier, go farther than cutting carbon emissions from power plants. He suggested that the federal government would set a goal of using 20 percent renewable energy, for example, and set a goal of reducing the government's emissions by 3 billion metric tons annually. He announced a focus on building infrastructure that could withstand the effects of the climate change he lambasted. His administration, he said, would also do something it hasn't really done to date: enter a leadership role in the international climate fight.

Eventually he turned to politics, and the need for action, not denial. "We don't have time for a meeting of the Flat Earth Society!" he exclaimed. "Sticking your head in the sand may make you feel safer, but it won't keep you safe from the coming storm." He demanded that the Senate approve Gina McCarthy, his nominee for administrator of the EPA, and asked Americans to "broaden the circle of those willing to stand up for the future" by championing his plan in their communities.

By cutting away early, the networks missed what was perhaps the most unexpected bit of news Obama laid out: that he would insist that the Keystone XL pipeline not result in an increase in greenhouse gas emissions. Even last night, during a call the administration held with members of the media, it was suggested that Keystone wouldn't be a topic of conversation. That the president would draw a red — or, rather, green — line on the controversial proposal was only revealed shortly before the speech.

For opponents of the pipeline, this will be surprising — and very welcome — news. For months, skeptics suggested that the president was likely to approve the pipeline; some saw today's announced crackdown on carbon dioxide as a potential point of leverage with environmental groups for the political space to approve the pipeline. But moreover, multiple recent studies, including one described by Scientific American in April have shown that the Keystone pipeline would indeed yield a net increase in greenhouse gas emissions. The pipeline will funnel a product called dilbit, diluted bitumen, from tar sands in Alberta to the Gulf Coast. The sludgy fossil fuel product uses more energy for extraction and processing than more conventional fuels, which could result in 181 million metric tons of greenhouse gas annually.

A draft environmental analysis released by the State Department in March downplayed that volume of emissions, primarily by assuming that the tar sands would be developed regardless of the existence of the Keystone XL pipeline — which is itself a debatable assumption. Regardless, the president could make a rhetorical point on Keystone today and then point to the draft State analysis as justification for approving the pipeline.

"And that's my plan," he concluded. He started to summarize — "The actions I announced today …" — but was interrupted by extended applause. As he began that second sentence again, another plane passed over, burning jet fuel and leaving carbon dioxide high in the air above.