Forests as a sink, or a very effective (and might I add, beautiful) way to remove CO2 from the atmosphere:

http://takvera.blogspot.in/2011/07/forests-play-major-role-as-carbon-sink.html

A great article on the measurement of how much Carbon is stored in forests:

Seeing Forests for the Trees and the Carbon_ Mapping the World’s Forests in Three Dimensions _ Feature Articles