By Walt Minnick

Not only are states, provinces and countries putting a price on carbon, but so are many companies. More than 430 major companies — including General Motors, Stanley Black & Decker and Colgate-Palmolive — are now using an internal price on carbon for internal planning and to make investment decisions, according to C.D.P. (formerly the Carbon Disclosure Project). More than a thousand companies worldwide, including most major hydrocarbon companies, are doing this or have pledged to do so within two years.