Much of the carbon dioxide released into the atmosphere from human activities — like burning fossil fuel — is taken up as plant food. Northern Arizona University’s Debbie Huntzinger, a researcher of climate change models, says the land’s surface is currently storing more of the greenhouse gas than it’s giving off.
“If you think of it like a checking account, as a whole the land surface acts as a net carbon sink. But, it’s unclear whether the land surface will continue to act as a net sink of carbon under changing climatic conditions or it will switch to a net source of carbon to the atmosphere,” she says.
Huntzinger says increased temperatures and changes in the amount of water and nutrients available may weaken the ability of plants to hold large amounts of carbon. But, scientists don’t know what that tipping point is. And, because there’s such a wide variety of land surfaces, different climate change models show different results. So Huntzinger is working with other scientists to compare studies.
“Each model is a team’s best attempt at modeling that complex system. So all are getting it partially right and partially wrong. As a community we don’t really know what pieces are missing from those models and so we’re working to identify where the gaps might be in order to improve our ability to model the system,” Huntzinger says.
Being able to predict how the land will process carbon dioxide in a changing climate is important, says Huntzinger, so that we might better manage or offset greenhouse gas emissions in the future.