A new paper out Jan. 23 in the journal Nature Climate Change by University of Montana researcher Ashley Ballantyne delves into one of the great uncertainties in predicting future climate.
"Will ecosystems take up more carbon or release more carbon as the climate changes?" Ballantyne said. "This is a key question in trying to predict what the climate might look like in the future."
Together with former UM doctoral student William Smith, Ballantyne investigated the sensitivity of these carbon feedbacks. While carbon dioxide has increased steadily over the last 50 years, Earth's temperatures have increased in an erratic stair-step pattern due to redistribution of energy in Earth system.
"We were curious to learn how Earth's carbon cycle responded during periods of rapid warming and periods of less rapid warming," Ballantyne said. "We discovered that the amount of carbon taken up by land ecosystems slows during periods of rapid warming and speeds up during periods of slower warming."
The researchers were surprised to learn that this speeding-up of carbon uptake during periods of slower warming was due mainly to less respiration from plants and not to greater photosynthesis. This means that during the so-called 'warming hiatus' from 1998 to 2012, Earth took up much more carbon from the atmosphere. However, as global warming ramps up again, this carbon may be returned to the atmosphere to further warm the planet.