* Photo: Heather Johnson * __Fred Krupp isn't __your typical tree hugger. Chided by radicals for wooing corporate partners, the president of the Environmental Defense Fund is revered in Silicon Valley for championing a capitalist approach to clean energy. His new book, Earth: The Sequel (with Miriam Horn), spotlights the most promising climate solutions, from nanotech to flying windmills. Wired asked Krupp how these technologies can compete.

Wired: Explain the title of your book.

Krupp: We've put Earth at the brink of climate calamity, thanks to rapid industrialization and market forces. That's part one. The sequel is how we get out of this fix. I believe it's those same forces, innovation and profit — and nothing else — that can stop global warming.

Wired: How so?

Krupp: In 1992, the EDF worked with Bush Sr. to craft a market system to reduce acid rain. It spurred a revolution in sulfur dioxide scrubbing technologies. The costs were projected at up to $2,000 a ton, but after 10 years they were down to about $100 a ton and emissions were slashed by 50 percent. In 2005, George W. Bush signed off on an additional 70 percent cut. Why? The costs proved so low, the political controversy had disappeared. I suspect the same thing can happen with a cap on global warming emissions once the incentives are right.

Wired: What kind of cap?

Krupp: A legal limit that requires reductions of at least 20 percent from current levels by 2020, ratcheting up to 80 percent by 2050. That'll give new technologies the chance to flower.

Wired: But won't our economy get hammered by China and India?

Krupp: It's inevitable that those countries will adopt caps, too. We will gain a competitive advantage by going first. The real question is, do we want to import clean tech from Germany, Japan, and China or export it to the rest of the world?

Wired: How fast will industry's costs decline?

Krupp: I can't say without claiming to know more than I do, but I know that capitalism works, that American entrepreneurialism works, and we can damn well expect that private capital — not government money — will actually solve this problem.

Wired: Why are so many of the leaders of the energy revolution the same folks who led the dotcom boom?

Krupp: It's the mindset: Silicon Valley entrepreneurs are willing to take risks. And many of the energy technologies are founded in computing sciences. But the energy business is much more capital-intensive than Web apps. And ultimately, clean tech is a much more important revolution. We're talking about the future of humanity, not how to find a date on the Internet.

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