Make no mistake: in one form or another, carbon emissions legislation, taxation and trading is a growing global trend. Aside from the environmental issues, taxing companies’ carbon emissions is simply too alluring a prospect for most governments to pass up. The challenge comes in accurately measuring exactly what a corporation’s carbon footprint is, and then facilitating the trading of credits. So it stands to reason that companies that help monitor, measure, and trade emissions credits might be interesting long-term investment opportunities.

Experts say measuring a company’s carbon footprint is notoriously difficult. It’s hard enough to measure the primary and secondary impact of, for example, mining companies or utilities. But how effectively can you measure the carbon footprint of a U.S. company that manufactures shoes in China for sale in the U.S?

There are four major exchanges for the trading of carbon credits: the Chicago Climate Exchange in the United States, the European Climate Exchange in England, Nord Pool in Norway, and PowerNext in France. Louis Redshaw, who is in charge of environmental markets at Barclays Capital, said “Carbon will be the world's biggest commodity market and it could become the world's biggest market overall."