SAN FRANCISCO - Nobel Peace Prize winner and former Vice President Al Gore announced Monday he's joining Silicon Valley's most prestigious venture capital firm to guide investments that help combat global warming.

Gore, an environmental activist who won an Academy Award for his global warming documentary "An Inconvenient Truth," joins Kleiner Perkins Caufield & Byers as it and dozens of other venture firms headquartered in Silicon Valley expand beyond software, computer hardware, the Internet and biotechnology to so-called "clean-tech" investments worldwide.

Gore is expected to be a high-profile, active partner at Kleiner Perkins. He's already a senior adviser to Google Inc. and a member of the board at Apple Inc. Alliance for Climate Protection, the advocacy group he co-founded, is based in Palo Alto.

Also Monday, Kleiner Perkins partner John Doerr announced he's joining the advisory board of Generation Investment Management, the $1 billion investment firm that Gore founded with David Blood, who previously managed $325 billion in assets out of Goldman Sachs' London office. Doerr is one of Silicon Valley's most outspoken clean-tech advocates.

Clean technology encompasses alternative fuels, water purification, renewable energy and recycling programs and other eco-friendly initiatives, as well as products ranging from electric cars to microbes that search for oil in seemingly tapped-out wells.

North American and European venture capitalists invested $1.9 billion in clean-tech companies in the first half of 2007, a 10 percent increase from the first half 2006, according to Ann Arbor, Mich.-based trade group Cleantech Network.

Last year, Menlo Park-based Kleiner Perkins earmarked $100 million of its $600 million investment fund to startups that work on reducing carbon dioxide emissions. The firm expects to dedicate one-third of new funding to clean tech by 2009.

In 2005, Kleiner Perkins named former Secretary of State Colin Powell a "strategic limited partner," but the moderate Republican hasn't played a prominent role in the firm's affairs.

Gore said in a statement that he'll donate 100 percent of his salary as a Kleiner Perkins partner to the Alliance for Climate Protection, which focuses on accelerating policy solutions to the climate crisis.

For years, Gore, 59, has been good friends with Doerr, a former Intel salesman who became a billionaire thanks to early investments in startups such as Netscape Communications, Amazon.com Inc. and Google.

They palled around together so much in the 1990s that fellow venture capitalist and former InfoWorld editor Stewart Alsop II created spoof political buttons that said "Gore and Doerr in 2004."