NEW LONDON, Conn. >> President Barack Obama used a commencement address Wednesday at the Coast Guard Academy to cast his push for urgent action to combat climate change as a national security imperative, saying that the warming of the planet poses an “immediate risk” to the United States.

The speech was part of an effort by Obama to make a multipronged case for his ambitious climate-change agenda, which he has identified as a top priority for the remainder of his time in office and as a central element of his legacy. Instead of promoting his plan strictly in environmental terms, he has pitched it as beneficial for the economy, necessary to protect public health and vital to the nation’s security.

“I am here today to say that climate change constitutes a serious threat to global security, an immediate risk to our national security, and, make no mistake, it will impact how our military defends our country,” Obama told about 4,200 people on an athletic field overlooking the water here, including about 200 graduates in crisp, white, dress uniforms. “And so we need to act, and we need to act now.”

Obama repeated arguments he cites often to promote his climate change effort, including a litany of grim facts and figures about rising temperatures, swelling seas and vanishing sea ice, dismissing skeptics of the phenomenon or those who refuse to act on it as guilty of “negligence” and “dereliction of duty.”

“I know there are still some folks back in Washington who refuse to admit that climate change is real, and on a day like today, it’s hard to get too worried about it,” Obama said on a sunny day cooled by a chilly sea breeze. “The science is indisputable. The planet is getting warmer.”

But Wednesday, he coupled those well-worn arguments with a national security-themed call to action to Coast Guard graduates just minutes before they received their commissions. He told the graduates that their generation would have to invent, build and pioneer the energy-efficient technologies that would be needed to reverse the damaging effects of climate change.

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