Al Gore has traveled the world to spread his message that climate change is creating a “planetary emergency.”

But there was one place Mr. Gore could not take his crusade: the White House.

That changed on Monday when, in a curious twist, President Bush invited his onetime political rival to the Oval Office.

The occasion was an annual tradition, the presidential photo opportunity with Nobel Prize winners. But former Vice President Gore, who shared the Nobel Peace Prize for his work on the environment, was granted special treatment: a private tête-à-tête with the president, which lasted more than 30 minutes, provoking intense speculation about just what the two talked about.

“Of course, we talked about global warming — the whole time,” Mr. Gore said afterward, as he and his wife, Tipper, emerged onto Pennsylvania Avenue, where they were mobbed by reporters and photographers.

No surprise there; Mr. Gore, whose documentary, “An Inconvenient Truth,” won an Academy Award, is a staunch critic of the Bush administration’s environmental policy. “He’s constantly looking for opportunities to make an impact on this issue,” said Michael Feldman, a Gore adviser, “so being invited to the political center of the universe is a great thing for him.”

Mr. Gore, however, was unwilling to say how great a thing it was — or wasn’t. As he and Mrs. Gore walked, like ordinary mortals, a block and a half from the White House to a nearby office building where, he said, a car was waiting, Mr. Gore struggled to fend off the inevitable questions about whether he missed the old place or was happy to be back.

“It was a private meeting,” he said, “and I’m not going to say anything about it other than that it was very nice, very cordial. He was very gracious in setting up the meeting, and it was a very good and very substantive conversation. That’s all.”