Gore has been one of the most outspoken critics of global warming and a powerful advocate of carbon-reducing measures. As such, he has become a hero of the left -- a man revered for warning Americans to curb their carbon footprint and reduce their impact on the Earth.

"Our Choice offers the most up-to-date and deepest thinking on climate change across a variety of disciplines," Gore said in a statement. "The need for this book is more urgent than ever, and I am proud to be working with Rodale, a company that for more than six decades has been at the forefront of environmental responsibility, to bring these solutions to a global audience."

Gore argues that in a market economy, "every one of the solutions to climate crisis will be more effective and much easier to implement if a price is placed on CO2 and other global warming pollutants," and likens the current sub-prime mortgage crisis to "the one we will face if we continue making investments in sub-prime carbon assets," according to publisher Rodale.

"The bottom line is that business and markets cannot operate in isolation from society and the environment -- we need 'sustainable capitalism,'" Gore said. And Gore has been practicing a particularly profitable form of capitalism of late.

Smart-Grid Company Could Hit Jackpot

One of Gore's investment that is poised to pay off royally is Silver Spring Networks, which produces hardware and software designed to make the electricity grid more efficient. Kleiner Perkins invested $75 million in the company to help it team up with local utilities to install smart-grid meters. Gore and VC titan John Doerr, a Google co-founder, joined the company as unpaid advisers.

It was a wise bet for Gore and Co. Last week, the Dept. of Energy said that $560 million of the $3.4 billion in smart grid grants it had approved would go to utilities which have partnered with Silver Spring, setting the company up for a major jackpot in coming years.

"Silver Spring Networks is a foot soldier in the global green energy revolution Mr. Gore hopes to lead," Broder writes. "Few people have been as vocal about the urgency of global warming and the need to reinvent the way the world produces and consumes energy. And few have put as much money behind their advocacy as Mr. Gore and are as well positioned to profit from this green transformation, if and when it comes."

Foes Fuming Over Gore's 'Green'

Gore, the co-recipient of the 2007 Nobel Peace prize for his environmental advocacy, has testified before numerous times before Congress, and given dozens of speeches based on his award-winning film An Inconvenient Truth, which portrayed an ominous future marked by ecological catastrophe.

To be sure, Gore has enemies, and many of them. He picked them up throughout a long career in public service, first as congressman, then as a senator -- he was dubbed Sen. Moonbeam -- then as vice-president to Bill Clinton, and finally as a green tech evangelist and ecological doomsayer.

Now these foes are fuming that Gore is poised to profit -- in a big way -- from investments in companies which seek to address the ecological crises he has been warnings about for years. Broder writes that Gore could be viewed as "profiteering from government policies he supports that would direct billions of dollars to the business ventures he has invested in."

At a hearing earlier this year, Representative Marsha Blackburn, a Tennessee Republican, attacked Gore for being poised to profit from the very policies he was urging the government to adopt.

"Do you think there is something wrong with being active in business in this country?" Mr. Gore responded. "I am proud of it. I am proud of it."

Nobel Prize Winner Defends His Investments

This week, Gore said that his investment activities were consistent with his public advocacy over decades. "I have advocated policies to promote renewable energy and accelerate reductions in global warming pollution for decades, including all of the time I was in public service," Gore wrote in an email message to the Times.

"As a private citizen, I have continued to advocate the same policies. Even though the vast majority of my business career has been in areas that do not involve renewable energy or global warming pollution reductions, I absolutely believe in investing in ways that are consistent with my values and beliefs. I encourage others to invest in the same way."

Gore has earned tens of millions of dollars since leaving the government at the end of the Clinton administration. He has served on the board of directors at Apple, the iconic computer, music and mobile company, as well as a outside adviser to Google, the Web search giant. During his time in the private sector, Gore has made a number of investments in green technology ventures, including projects making solar cells and waterless urinals.

$35 Million Investment Hints at Wealth

As a private citizen, Gore does not have to disclose his income or assets, as he did in his years in Congress and the White House, but when he left government in early 2001, he listed assets of less than $2 million, including homes in suburban Washington and in Tennessee. "Since then, his net worth has skyrocketed, helped by timely investments in Apple and Google, profits from books and his movie, and scores of speeches for which he can be paid more than $100,000, although he often speaks at no charge," Broder reports.

Today, Gore does not reveal his net worth, but the fact that he was able to single-handedly make a $35 million investment in Capricorn Investment Group, a private equity fund started by his friend Jeff Skoll, the Silicon Valley entrepreneur and film producer, speaks volumes about the magnitude of his wealth.

Some of Gore's private sector green tech activities include:

· Founder of, and investor in, London-based Generation Investment Management, which is run by David Blood, a former head of Goldman Sachs Asset Management

· Partner at, and investor in, Kleiner Perkins.

· Invested in partnerships and funds that try to "identify and support companies that are advancing cutting-edge green technologies and are paving the way toward a low-carbon economy."

· Stake in "the world's pre-eminent carbon credit trading market and in an array of companies in bio-fuels, sustainable fish farming, electric vehicles and solar power."

· Adviser to high-profile technology companies including Apple and Google, "relationships that have paid him handsome dividends over the last eight years."

· Capricorn has invested in Falcon Waterfree Technologies, the world's leading maker of waterless urinals.

· Generation has holdings in Ausra, a solar energy company based in California, and Camco, a British firm that develops carbon dioxide emissions reduction projects.