tree butress_SRP_0730 (IMAGE) Smithsonian Tropical Research Institute Caption Tropical forests pull carbon dioxide out of the atmosphere where it causes global warming and store it as wood. But the amount of carbon stored varies depending on tree species, age, climate conditions and other factors. Verifiable estimates of carbon stored in forests are necessary to calculate carbon credits. Credit Credit: Steve Paton, STRI Usage Restrictions Credit: Steve Paton, STRI License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.