The founder of the Virgin Companies, Sir Richard Branson, isn’t a stereotypical stuffed-shirt CEO. He’s a marijuana evangelist, a celebrity prankster, and an around-the-world hot air balloonist. His formalwear often consists of an untucked shirt and jeans.

Now the 56-year-old Briton is doing something else wildly out of the ordinary for a billionaire mogul: using 100% of the profit from his transportation companies over the next 10 years to fund efforts to rein in global warming.

“A lot of aughts,” Mr. Branson joked as he looked at a ceremonial certificate listing the $3 billion — that’s nine zeros — he is promising to invest over the next decade to develop sustainable energy sources.

Mr. Clinton added, “No matter how cynical you are, that’s serious money.”

Mr. Branson announced the donation yesterday, the second day of the Clinton Global Initiative, an annual meeting of international luminaries hosted by President Clinton. This year, the three-day conference, held at the Sheraton hotel in Times Square, attracted nearly 1,000 academics, philanthropists, heads of state, CEOs, Hollywood stars, and nongovernmental organizations, who all gathered to “tackle big global challenges in bite-sized pieces,” as Mr. Clinton said Wednesday.

Guests yesterday included the secretary of state during President Bush’s first term, Colin Powell, the Reverend Jesse Jackson, President Karzai of Afghanistan, and Queen Rania Al-Abdullah of Jordan.

The $3 billion commitment is a continuation of Mr. Branson’s philanthropic efforts, the managing director of his foundation, Jean Oelwang, said. The billionaire established the foundation, called Virgin Unite, in 2004 to help manage his potpourri of charitable ventures.

Over the past several decades, Mr. Branson has launched ventures as various as a counseling center and a condom brand, in addition to traditional businesses like an airline and a music store chain.

He became interested in the environment when Vice President Gore visited him in London about a year ago, he said.

The vice president said that if Mr. Branson “could make a bold gesture, then maybe other people will make a bold gesture as well,” Mr. Branson said.

Mr. Clinton also announced yesterday a $40 million endowment by Jonathan Tisch to fund a public-service college at Tufts University, $10 million from the German telecommunications company Siemens for medical diagnostic equipment in China, and $100,000 from Sustainable South Bronx and Bradco Supply for greenery in the South Bronx.

Also yesterday, Mr. Gore gave an in-person, one-man rendition of sorts of his movie, “An Inconvenient Truth,” and challenged businesspeople in the audience to help address climate change because, he said, global warming is pushing the planet toward environmental catastrophe.

“I think there’s a task for the business community in policing the irresponsible voices in the business community — like ExxonMobil, for example, spending all this money to intentionally confuse the public’s understanding of what this is all about,” Mr. Gore said to applause. A camera feeding two large video screens in the hotel ballroom panned to Mr. Clinton, who was clapping. Next to him sat the long-haired Mr. Branson.

Shortly afterward, the two men joined Mr. Gore on stage to sign a ceremonial document committing Mr. Branson to the $3 billion. As Messrs. Clinton and Gore stood next to each other and signed the documents, Mr. Gore said, “It’s like the old days.”