It's amazing what thoughts of a legacy will do. With little more than six months left in his administration, President Bush has finally agreed to join other industrialized countries in setting a goal to reduce the greenhouse-gas emissions that fuel global warming. It's progress of a sort that some oxygen has been added to the leadership vacuum in the White House on this crucial issue.

Ever since his first inauguration, Mr. Bush has been resistant to the evidence of climate change, moving as if through stages of grief from denial to grudging acceptance without actually achieving much. Now he offers what he calls "significant progress" after G-8 leaders meeting in Japan pledged to meet some benchmarks.

But the significance of this progress is open to debate. Mr. Bush has at least faced up to the fact of global warming and pressed for concerted international action in a way that goes beyond past lip service. The immediate significance of his action was that it defied his core constituency -- that legion of unscientific pundits and talk-show listeners who remain convinced that man-made climate change is a hoax and science be damned.

Fortunately, most Americans are smarter than that, understanding that we cannot go on fouling our nest, the Earth, without inviting calamity and that sensible steps taken now may forestall drastic measures later.

For Mr. Bush, this growing political consensus leaves him exposed to the judgment of history. And history may not be impressed by the postscript he now adds to his general record of underachievement, but for the moment it is a case of better late than never.

The G-8 member nations -- the United States, Britain, Germany, France, Italy, Canada, Japan and Russia -- agreed to cut greenhouse-gas emissions by 50 percent by 2050. That is certainly good in theory, but no numerical targets were agreed to and no starting point was specified. It was also commendable that, at Mr. Bush's urging, the developed nations expanded their talks to include the emerging economies of China, India and six other nations.

But the attitude of the developing nations is problematic. These nations, which came last to the industrialization party, do not believe that sacrifices in combating global warming should fall equally on them when they were not the main culprits in causing the problem in the first place. Like so much else for the Bush administration, the difficult challenge of sorting this out will fall to a new president.

While Mr. Bush has done the right thing at last, the fact remains that the Bush years saw the squandering of a great window of opportunity to do something earlier about a global problem. This late window dressing may not be enough to redeem his legacy, but for the sake of the planet we hope that this action is truly significant.