Branson, the billionaire behind the multi-platform Virgin brand, said the money would come from the profits generated by his transportation and airline sectors. It will then be invested in efforts to find renewable, sustainable energy sources in an effort to wean the world off oil and coal.
He made the announcement in Manhattan on the second day of the Clinton Global Initiative, an annual conference of business, political and nonprofit leaders hosted by former President Clinton.
"Our generation has inherited an incredibly beautiful world from our parents and they from their parents," said Branson at a press conference with Clinton at his side. "We must not be the generation responsible for irreversibly damaging the environment."
Clinton praised Branson, calling him one of the most "creative" and "committed" people he's ever known.
The commitment ensures that the conference, which brings people together to brainstorm tangible solutions to global issues, would more than meet its goal of matching last year's efforts. In 2005, the conference resulted in more than $2 billion in pledges.
The initiative began Wednesday with a slew of world figures, from first lady Laura Bush to Pakistan President Pervez Musharraf. On Thursday, the opening session featured Afghanistan President Hamid Karzai and Queen Rania al-Abdullah of Jordan.
The gathering, in its second year, brings together government, business and nonprofit sectors in an effort to spur action on poverty, health care, global warming and religious/ethnic conflict.
Clinton's wife, Sen. Hillary Rodham Clinton, D-N.Y., was to attend, as was his former vice president, Al Gore. Other speakers expected on Thursday included former President Jimmy Carter and champion cyclist Lance Armstrong.