At the start of his speech Tuesday morning on environmental policy, President Obama encouraged everyone in the Georgetown University audience to take off their jackets. (The high in Washington, D.C. today: 94 degrees, while "humidity levels continue in the discomfort range.") And he quickly joined them, prompting a chorus of "ooohs" from an audience that mixed college students and environmental activists.

"It's not that sexy," the president replied.

The more substantive news out of Obama's speech: He will not approve the Keystone XL pipeline if building it would generate more greenhouse-gas emissions than not building it.