OOS 2-1 - Observing carbon cycle-climate feedbacks from space

Monday, August 7, 2017: 1:30 PM
Portland Blrm 255, Oregon Convention Center
David S. Schimel, Climate Sciences, Jet Propulsion Lab, California Institute of Technology, Pasadena, CA, Junjie Liu, JPL, Pasadena, CA and Abhishek Chatterjee, GSFC, Greenbelt, MD

What controls the rate of increase of CO2 and CH4 in the atmosphere? It may seem self-evident but actually remains mysterious. The increases of CO2 and CH4 result from a combination of forcing from anthropogenic emissions and Earth System feedbacks that dampen or amplify the effects of those emissions on atmospheric concentrations. Today, emissions from fossil fuel combustion and land use are partitioned between the atmosphere, where they affect the climate, and a series of poorly understood sinks, such as changes in terrestrial primary production. If these sinks change, the climate effect of the human enterprise will change. Much about the carbon-climate system, despite decades of research, remains without satisfactory answers; in the wake of recent climate negotiations, these uncertainties are unacceptable. Emissions, long concentrated in the developed world, are now increasingly distributed globally with large uncertainties, leading to uncertainty about forcing to the carbon system. Long-term observations of atmospheric CO2 strongly suggest the existence of both positive and negative feedbacks from terrestrial ecosystems, but quantifying these and projecting into the future has remained uncertain.


New satellite measurements of ecosystem state and function, linked together by estimates of carbon fluxes constrained by satellite observations of CO2 are revealing ecosystem feedbacks in unprecendent ways. These new estimates of biomass, photosynthesis and Net Biome Exchange from space provide a fumdamentally different view that can be obtained with only sparse surface observations, while relying on and increasing the value of the surface observations. These new observations provide constraints on the climate sensitivity of ecosystems, as well as a new constraint on CO2 fertilization. In this talk, I'll review the nature of the new technology, the process for converting physical observations into ecosystem fluxes and some emerging new results about how ecosystem respond to and influence climate.