WASHINGTON - In a Capitol Hill debate about global warming touted by its moderator as a "smackdown" between former House speaker Newt Gingrich and Senator John F. Kerry of Massachusetts, Gingrich praised Kerry's recently released book about environmentalism, acknowledged that global warming is real, and offered what amounted to an unexpected apology for his party's inaction on curtailing greenhouse gas emissions.

The standing-room-only debate, staged yesterday in an ornate Senate hearing room, offered an indication that even diehard conservatives like Gingrich, who stepped down as speaker in 1998, are abandoning their skepticism on global warming. As recently as two years ago, Gingrich ridiculed the notion that humans are causing the earth to warm, but yesterday he said the evidence was "sufficient."

Among conservatives yesterday, reaction to Gingrich's performance at the debate ranged from puzzled to outraged, and several bloggers accused the former speaker of betraying the GOP by caving to the environmental lobby. A critical post on the website of the conservative magazine National Review was titled, "There goes Gingrich '08?"