It was snowing in Washington, D.C., on Tuesday morning as hundreds gathered to ask for action — the kind of omen that those of us who obsess about global warming look for. Maybe the incoming Obama administration really is ushering in a new climate to our nation’s capital!

The president-elect certainly sent a strong signal to that effect, capping the day with the strongest words we’ve heard yet from an American leader on the topic.

Speaking via (low-carbon) video to a California gathering, Obama said that the continued existence of George W. Bush as president would prevent him from making the trip to Poland next month for the next round of international talks. But he’d clearly heard the call for his presence — including the more than 50,000 invitations from every corner of the world that came through the 350.org website.

“While I won’t be president at the time of your meeting and while the United States has only one president at a time, I’ve asked members of Congress who are attending the conference as observers to report back to me on what they learn there,” he said. Better yet, he added this: “And once I take office, you can be sure that the United States will once again engage vigorously in these negotiations, and help lead the world toward a new era of global cooperation on climate change.”

The activists gathered outside the Capitol in the morning flurries heard from Maryland Rep. Chris van Hollen, a rising star in the party (he chaired the Democratic Congressional Campaign Committee that added 20 seats to the party’s roster) issue a strong call for early action after eight wasted years of the Bush administration.

He was flanked by an enormous and intricate 350 quilt, hauled from California by its maker, Ulla Nilsen. Mike Tidwell, who heads Chesapeake Climate Action Network, also addressed the gathering, as did Gillian Caldwell from 1sky, and representatives from Greenpeace, local faith groups, and the International Forum on Globalization.

The focus was fascinating — more and more U.S. activists are clearly as concerned with global re-engagement as with domestic emissions cuts. Which makes sense, since they are the one-two punch of effective action, each useless without the other. As Obama said in the coda to his talk, once he takes office “any nation that’s willing to join the cause of combating climate change will have an ally in the United States of America.”

All in all, there have been few days in the dismal 20-year history of global warming when Americans could feel more entitled to hope.