LONDON—Analysts are predicting that the $3 billion Sir  Richard Branson has pledged for developing energy sources to combat global warming could come close to matching the amount the entrepreneur, adventurer, and Virgin CEO has already spent on elaborate balloon-based excursions.

"This unprecedented and extremely generous investment rivals the amounts Branson spent on his many, many failed attempts to circumnavigate the Earth in a balloon," Wall Street stock analyst Madeleine Brauner said. "He's setting a wonderful example for ultrarich environmentalists everywhere."

Branson also reportedly plans to invest billions more on a time machine that would enable him to prevent the creation of Virgin Airways, reducing greenhouse-gas emissions by some four percent worldwide.