Sunday, December 18, 2016

The need to speed up carbon uptake

Last week I gave a talk, entitled "Net Ecosystem Production and Actionable Negative Emissions Strategies," at the American Geophysical Union (AGU) fall meeting in San Francisco. It was presented in a session on negative emissions strategies, which refers to the topic of removing CO2 from the air in order to slow -- and hopefully one day reverse -- the buildup of carbon in the atmosphere.

Net ecosystem production (NEP) is the net rate at which carbon is taken up by a terrestrial ecosystem. It determines the amount of carbon that becomes available for some use (e.g., crop or timber harvest) or for sequestration on the land. Scientifically speaking, any parcel of land with living organisms on it is an "ecosystem," including farm land or managed forests as well as natural lands and parts of the built environment that aren't totally paved with sterile concrete.

Plants and other organisms that carry out photosynthesis in the terrestrial biosphere actively remove CO2 from the air. Thus, they provide a fundamental mechanism for pursuing negative emissions. However, to be meaningful for climate mitigation -- which is the sense in which the term negative emissions is used -- carbon must be removed from the air more quickly than it is already being removed. That's what "the need to speed up carbon uptake" means and for the terrestrial biosphere, that means increasing NEP.

The fact that terrestrial carbon management is an actionable ("here-and-now") strategy and that using it for negative emissions requires increasing NEP are the main points of my talk. It can be download here in PDF format including both the narrative and slide images.

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