When Obama arrives in Copenhagen tomorrow to support Chicago’s 2016 Olympic bid, he will be showing the world that he is willing to schlep to Scandinavia for an event he considers important. The big question now is: will he do it again on December 7, when Copenhagen plays host to the United Nations summit on climate change, the highest-stakes environmental negotiations in history?

British Prime Minister Gordon Brown has already pledged to be there, characterizing the summit as a last chance to pull the planet back from the brink. “I will go to Copenhagen to conclude the deal,” Brown told the UN General Assembly. “This is too important an agreement–for the global economy, and for the future of every nation represented here–to leave to our official negotiators. So I urge my fellow leaders to commit themselves to going to Copenhagen too.”

No word so far on the whether Obama will heed the call (remember that George Bush Sr. went to the Rio Earth Summit). Considering the Obama administration’s paltry proposals on emissions cuts, and the total absence of a US plan to help developing countries meet the massive costs associated with a climate crisis they did not create (ask the residents of flooded-out Manila…), it’s not surprising that the president might want to avoid what promises to be a angry showdown in Copenhagen. Already US negotiators are trying to lower expectations for what the summit can accomplish, an ominous sign.

One thing is certain: if Obama skips Copenhagen in December, after making time to go there to promote the Olympics in October, he will be saying something chilling about his administration’s commitment to battling global warming. Now is the time to tell Obama: you’d better go back to Copenhagen.