Solar stocks like First Solar ( FSLR) were getting beaten down throughout 2011 and early 2012, but since hitting a low of about $12/share in June (from a high of $168/share) FSLR has rebounded to a price of over $30/share. The recovery has yet to hit the main solar ETFs -- KWT ( KWT) and TAN ( TAN) -- which are still bouncing near those June levels. KWT currently has 13% of its valuation in FSLR while it's the second-largest holding in TAN. TAN is slightly more diversified , being in money-losing solar wafer maker MEMC ( WFR). Both hold a lot of shares in Chinese companies that are being beaten down for reasons outside the industry. So while a carbon tax would be tough to design and hard to pass, it would (unlike many other taxes) provide some interesting investment opportunities. I wouldn't sell my oil and gas stocks with a carbon tax -- demand for energy continues to rise -- but I wouldn't run for the hills, either. Speculation is starting to rise about President Obama's next State of the Union address. He has said, once or twice, that in his second term he wants to address the problem of climate change. He has also said he wants to cut our deficits. I fully expect a proposal for a carbon tax, and you shouldn't be gobsmacked if one comes. Maybe we can finally start to pay for two of the longest wars in American history. Maybe we can keep your grandchildren from living on a planet that's hotter than Hades. And maybe we can make some money along the way. At the time of publication the author had a position in GE.Follow @DanaBlankenhornThis article was written by an independent contributor, separate from TheStreet's regular news coverage.