Financial risk from carbon costs is greatest in the Utilities sector, where EBITDA at a company level could fall by 2% to 117%."

As for mutual funds, they, too, vary widely in terms of their carbon exposure -- sometimes in unexpected ways. Trucost’s report, called Carbon Counts USA, examined the carbon performance of 91 mutual funds in the U.S., including 16 funds that say they focus on sustainability or socially responsible investing. It did not make all the results public, but it said “the footprint of the most carbon-intensive fund is over 38 times larger than the lowest-carbon fund, reflecting the range in potential carbon risk.”As you’d expect, the 16 funds that focus on sustainability or social investing have, as a group, the smallest carbon footprint, but some are much “greener” than others. Trucost found that the Sentinel Sustainable Core Opportunities Fund has a carbon intensity (692 tons of carbon equivalent emissions per $1 million of revenues of the fund’s holdingss) that is seven times as great as the Ariel Appreciation Fund, which has the smallest footprint (98 tons of carbon equivalent emissions per $1 million in revenues.) Green Century, meanwhile, reports that its footprint is 126 tons of carbon per $1 million in revenues, bigger than the Ariel Fund but just a bit more than half of the average of the sustainability funds tracked by Trucost. The 10 biggest holdings of the Green Century Balanced Fund, as of March 31, were IBM, AT&T, Xerox, Federal Home Loan Bank of Chicago, General Mills, SLM Corp., Telfonica SA, Johnson & Johnson, Advance Auto Parts and Oracle. Gustav Knepper Power Station in Dortmund, Germany What does this all mean? It’s too soon to say. Only over time will we be able to see whether low carbon stocks and funds, as a group, outperform those with higher carbon exposure. Already, though, some investors are factoring carbon into their long-term view. Trucost is using its data to develop investable indexes of low-carbon companies. “If enough investors look at carbon intensity,” Krosinsky tells me, “it will create a competitive dynamic and encourage companies to become more efficient.” More capital would then flow to clean tech, and less to coal plants like the one to the left.