A recent study from the London School of Economics produced some findings that could be seen as a blow to proponents of aggressive investment in emerging green technologies: investments in contraception are five times more effective in reducing carbon emissions than green energy technologies like wind and solar power.

The symbol of the green movement shouldn't be a wind turbine. It should be a condom.

Investors hoping to ride the climate change bandwagon have had a roller coaster ride over the past two years. Greentech stocks soared with the oil spike in 2007 and 2008, then crashed with stock market and commodity price declines in 2009. Since then, some of the most obvious stock plays have strongly rebounded. Many solar stocks have posted high double-digit gains since rebounding off year-to-date lows in March 2009.

The leading solar panel manufacturer, FirstSolar (NASDAQ: FSLR) has appreciated by 45% from lows of near $100 to a closing price of $154 on October 14. "I wouldn't be stepping into buying these stocks right now," says Pacific Crest senior analyst Mark Bachman, who covers solar stocks. Still, he rates FirstSolar as a market perform and considers it the best solar stock at present on his coverage list.

Venture capital investment in clean technology grew 10% from the second quarter to the third this year. According to a report by the Cleantech Group and Deloitte, 134 companies received investments of $1.59 billion – up from $1.2 billion in the second quarter. The sector's upward trajectory continues, with last quarter marking the second in a row of double-digit growth. In the first quarter of 2009, venture capital investment in cleantech companies hit a low of $1 billion.

The strong third quarter has made the cleantech sector the largest in the venture capital business, according to the Cleantech Group, pulling ahead of biotech. Twenty-seven percent of venture capital funds invested in the second quarter of 2009 went to cleantech companies – up from 3% at the beginning of 2004.

Not long ago, Al Gore seemed like a has-been. Then he snagged both an Academy Award and the Nobel Peace prize.

Will these accolades persuade him to run for president again?

Perhaps not. Perhaps there are more effective ways to enact sweeping change. To wit: Gore has become a partner at the esteemed venture capital firm, Kleiner Perkins Caufield & Byers. The firm has invested in such game-changing companies as Google (NASDAQ: GOOG), Intuit (NASDAQ: INTU), and Amazon.com (NASDAQ: AMZN).

This is the seventh in a series of trend-spotting tips from Hilary Kramer's newly-released book, Ahead of the Curve.

Everyone knows imagination and creativity are essential for entrepreneurs -- after all, they're the visionaries who see things that don't already exist, and then figure out a way to make them exist. But it's also essential for investors to be imaginative in thinking of ways to make money, and then investing in companies that share their vision.

To take an example, a few years ago, only a science-fiction fan or a dreamer would have thought we could power cars off plants in the ground. Everyone knew about ethanol, of course, but who would ever have thought we could use almost any biological matter to get ourselves to work in the morning?