The Defense Department Web site informs us:

“The area of climate change has a dramatic impact on national security,” Panetta said here at a reception hosted by the Environmental Defense Fund to honor the Defense Department in advancing clean energy initiatives. “Rising sea levels, severe droughts, the melting of the polar caps, the more frequent and devastating natural disasters all raise demand for humanitarian assistance and disaster relief,” Panetta said. . . .

The secretary also said he has great concern about energy-related threats to homeland security that are not driven by climate change.

“I have a deep interest in working to try to ensure from a security perspective that we take measures that will help facilitate and maintain power in the event of an interruption of the commercial grid that could be caused, for example, by a cyber attack which is a reality that we have to confront,” he said.

Not to worry, however; the Defense Department will be “investing” $2 billion in energy-efficient equipment and installations. (No mention was made of the fuel costs entailed in Panetta’s frequent flights home, which have rung up an $800,000 tab while military personnel and their families are expected to do more with less).

We will not, however, be investing much in national security. While Panetta goes green, the Pentagon is going into the red.

Recall that the sequestration of defense funds as a result of the Budget Control Act — which Panetta labeled “devastating” (maybe not as much as the polar ice caps’ meltage, but close) — are due to go into effect in less than a year. The president said he’s dead set against coming up with alternative cuts.

Defense hawks’ reaction to the Panetta environmental powwow ranged from incredulous to irate. A House Republican aide retorted: “What is the Secretary doing bumping elbows with the environmental lobby when he should be cracking skulls to turn off sequestration?” Umm . . . because environmentalists will listen to him and the president won’t? From the aide’s standpoint, this personifies the administration’s misguided priorities. He asked indignantly: “How many divisions does global warming have?”

A Senate Republican wisecracked. “Next up, he nominates Al Gore as Chairman of the Joint Chiefs.” He circled back with me to emphasize this was a joke, but his disgust was real.

Thomas Donnelly of the American Enterprise Institute told me: “The impulse to describe every issue — the economy, the environment, energy efficiency — as elements of ‘national security’ is dangerously confusing America. If everything counts as a security concern, then nothing really does.” And of course, it masks the fact that the actual resources of the real military (the people who break things and kill the bad guys) are being stripped away like bark from trees in the rainforest.

In March, The Post’s Robert Samuelson explained that the $500 billion in cuts are on top of other cuts already enacted (the magnitude of which has not been matched on the domestic side of the budget):

These [cuts]are in addition to the $487 billion in defense reductions already in the [Budget Control Act] and billions of earlier cuts ordered by former defense secretary Robert Gates, who ended some major programs including the F-22 stealth fighter. Nor do these cuts count the automatic reductions occurring from withdrawals from Iraq and Afghanistan. Even without sequester, defense spending is estimated to fall to 13 percent of the budget in 2017.

Defense Secretary Leon Panetta has repeatedly denounced the sequester. In a letter in November to Republican Sens. John McCain of Arizona and Lindsey Graham of South Carolina, he called the prospective cuts “devastating.” After a decade, they would result in “the smallest ground force since 1940, the smallest number of ships since 1915, and the smallest Air Force in its history.” Testifying Feb. 16 before Congress, he said sequestration “would . . . inflict severe damage on our national defense.”

Even the threatened sequester has bad effects, argue defense analysts Michael O’Hanlon of the Brookings Institution and Mackenzie Eaglen of the American Enterprise Institute. It weakens the president’s ability “to signal Iran, North Korea and China that the United States remains as firmly committed to our interests and allies as ever.”

While Panetta blathers on about global warming (how much time and money do you think his counterparts in Russia, China, Iran and elsewhere spend on this stuff?), his department and our national security are being sacrificed, not for fiscal prudence but to keep funding the uptick in entitlements and discretionary spending.

Rather than metaphorically riding the Pentagon float in the Earth Day parade, maybe Panetta should be trying to defend defense — or resign as a matter of principle (do people still do that?) to protest a president’s policy that would intentionally devastate our national security.