Do trees cause global warming? - Darren Samuelsohn - POLITICO.com

Jay Gulledge, a senior scientist at the Pew Center on Global Climate Change, said Rohrabacher is correct that 80 to 90 percent of gross greenhouse gas emissions do come from nature, with humans producing the rest.

Greenhouse gas - Wikipedia, the free encyclopedia

Natural sources of carbon dioxide are more than 20 times greater than sources due to human activity