Project: Quantifying Carbon Cycle-Climate Feedbacks with the GFDL Earth System Model

Organization/Location: Princeton University, Princeton, New Jersey

Advisers: Jorge Sarmiento, George J. ­Magee Professor of Geoscience and Geological ­Engineering, Director, Program in Atmospheric and Oceanic Sciences (AOS); Keith ­Rodgers, Research Scholar, AOS. Thomas Frolicher, Postdoctoral Research Fellow, AOS

This summer I worked with the Sarmiento group in the Atmospheric and Oceanic ­Sciences Program on quantifying carbon cycle-climate feedbacks in Earth System ­Models. ­Currently about half of anthropogenic carbon emissions remain in the ­atmosphere, with the remainder taken up by the carbon sinks that make up the carbon cycle. ­However, the amount of carbon removed from the atmosphere through these processes is ­projected to increase as atmospheric CO₂ increases and climate change progresses. This creates a feedback between the carbon cycle and climate system which can exert a great deal of influence on the rate and degree of climate change. Climate models have different ways of characterizing this and other feedbacks, which is one reason for the uncertainty in projections between different models. Climate scientists have tried to characterize the extent of these feedbacks by using linear feedback factors. These can be easily compared between different models and useful for examining inter-model uncertainty. By creating such feedback factors, I was able to compare the ­uncertainties between different Earth System Models. In addition, I examined how intra-model ­variability affects feedback factors and discovered that uncertainty within climate models could result in a slightly smaller or larger spread of climate change projections.