NEW LONDON, CT (AP) — President Barack Obama said May 20, 2015, the threat posed by climate change is evident all around and that those who deny the “indisputable” science that it is real are putting at risk the security of the United States and the military sworn to defend it. Obama said refusing to act to slow the effects of global warming, including rising seas, amounts to a “dereliction of duty” and undermines the readiness of U.S. forces, including of the 218 graduates of the U.S. Coast Guard Academy in Connecticut, where he delivered the commencement address.

“I’m here today to say that climate change constitutes a serious threat to global security, an immediate risk to our national security,” Obama said, focusing his remarks on an issue that he told the cadets cuts to the “very core of your service.”

“It will impact how our military defends our country. And so we need to act — and we need to act now,” he added. “Denying it or refusing to deal with it endangers our national security. It undermines the readiness of our forces.”

The president has pressed in recent months for action on climate change as a matter of health, as a matter of environmental protection and as a matter of international obligation. He’s even couched it as a family matter, linking it to the worry he felt when one his daughters had an asthma attack as a preschooler.

But with the Republican-led Congress indifferent to Obama’s entreaties, the president has been doing what he can to combat climate change on his own through executive orders to cut greenhouse gas emissions and through the powers of persuasion. His climate change agenda also has drawn strong political opposition and legal challenges, and many of the GOP presidential candidates have said that taking unilateral steps to address climate change could hurt the U.S. economy.

Obama focused his speech to the cadets on what he says are immediate risks to national security, including contributing to more natural disasters that cause humanitarian crises and potential new flows of “climate change” refugees. Further, the president sees climate change as aggravating poverty and social tensions that can fuel instability and foster terrorist activity and other violence.

Obama said the cadets will be among the first generation of officers to begin their service in a world where it is increasingly clear that “climate change will shape how every one of our services plan, operate, train, equip and protect their infrastructure.”

“This is not just a problem for countries on the coasts, or for certain regions of the world. Climate change will impact every country on the planet,” he said on a crisp, sunny morning on Cadet Memorial Field, where the cadets sat in their white uniforms with friends and family looking on from the bleachers.

As for the impact in the U.S., Obama pointed to streets in Miami and Charleston, SC, that flood at high tide and to military bases around the country already feeling negative effects.

“Around Norfolk, high tides and storms increasingly flood parts of our Navy base and an air base,” Obama said of military facilities in Virginia. “In Alaska, thawing permafrost is damaging military facilities. Out West, deeper droughts and longer wildfires could threaten training areas our troops depend on.”

Obama’s appearance at the academy was his second and final commencement address of the season, after speaking earlier this month at a community college in South Dakota. The president traditionally delivers a commencement address every year to one of the military service academies.

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