U.C. Davis graduate student Mason Earles helped with the study.  He says as much as 40 percent of the carbon in clear-cut trees hasn't been released into the atmosphere -decades after the trees were cut.  That's because the timber was used for housing materials or other things requiring wood.

EARLES:  "Originally, the studies and models had assumed that following deforestation, all of the carbon that was stored on a piece of land was emitted into the atmosphere immediately. Our study suggests that the picture is much more complex than that and it depends on which country you're in."

In the U.S. and Canada, wood-based products other than paper are common and emissions from cleared land were down substantially compared to countries like Brazil. In South America and Malaysia clear-cutting is common as forest land is turned into crop land for corn and sugar cane to make ethanol.