Americans who want to see action on climate change are ready for the United Nations summit which just opened in Copenhagen and will be watching it with great interest.

Some, of course, are still skeptical about the science of the issue. Note the undue attention paid to e-mails hacked from a computer server at a British university that supposedly shows an attempt by certain climatologists to inflate the data on global warming -- despite overwhelming evidence elsewhere that the data look dire enough.

Some are also troubled by the cost of measures that could emerge from the summit for curbing harmful emissions. Their concern over the cost is sharpened by the state of the American economy and the fiscal condition of the U.S. government.

The estimated cost of measures to deal with global warming, however, should not drive the discussion of this subject. It is certainly correct to ask where this challenge lies in terms of U.S. priorities, but if it isn't high on the list America is being shortsighted and irresponsible.

The fussing about the science is an attempt to head off the world from what it needs to do. Independent groups of scientists, from different countries and with different political beliefs, report that the North Pole ice pack and mountain-top glaciers are melting, and -- the latest -- that the past decade was the warmest at least since such records have been kept.

Some of the proceedings in Copenhagen no doubt will be posturing. Some developing countries see the developed world's attempts to tackle global warming as another opportunity to leverage aid, for instance.

What will be critical, and what Americans should want, is that Mr. Obama and the United States provide leadership to the rest of the developed world -- America's friends, the G-20 -- on attacking the problem. It will be important for him to pledge the United States to measures consistent with its leading role in creating and dealing with the problem, and then bring the American people and Congress along with him on follow-up actions afterward.

But the United States can't do it alone. All nations, large and small, rich and poor, must take up the cause of a sustainable environment and work to reduce harmful air emissions.

This is a case where our children and grandchildren will judge us for what we do, or don't do. The world does not have time for its leaders to fool around.

Cartoonist Rob Rogers does "Rob's Rough," an early look at his work and his creative process, exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.