But what, exactly, does becoming carbon neutral mean?
It turns out that there's no agreed-upon definition of carbon neutral, even as rock groups like the Rolling Stones, events like the Super Bowl and the Oscars, and a growing number of companies have set carbon neutrality as a goal.
Among them, and this is by no means a complete list, are such well-known firms as Google (GOOG, Fortune 500), HSBC (HBC), Swiss Re, Timberland (TBL) and Yahoo (YHOO, Fortune 500) (You can read about Google's plans here, HSBC's here, Swiss RE's here, Timberland's here and Yahoo's here.) Some are already carbon neutral, others still on the way.
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