Development of an Implementation Plan for Atmospheric Carbon Monitoring in California

Abstract

This report describes the design of atmospheric CO 2 concentration measurements that, in combination with other measurements and models, would be used to quantify regionally distributed CO 2 exchanges from California's terrestrial ecosystems and CO 2 emissions from fossil fuel combustion. Using models of net ecosystem CO 2 exchange (NEE), fossil fuel CO 2 emissions, and regional meteorology, we predict CO 2 concentration "signals" in the atmosphere. The predictions of NEE exhibit spatial and temporal variations that are controlled by land cover and climate. Fossil fuel CO 2 emissions from metropolitan areas are the strongest localized sources of CO 2 while weaker but spatially extensive fossil emissions are present throughout the Central Valley. We subdivide the CO 2 sources into four components: NEE inside and outside CA, and fossil fuel CO 2 inside and outside CA. Maps of predicted atmospheric CO 2 concentration signals from these four sources largely mirror the instantaneous emissions near strong sources but plumes of CO 2 enriched or depleted air are predicted to advect far from their sources. We then identify a baseline set of observing stations from existing and possible future sites that could be used to characterize in-state and out-of-state ecosystem and fossil fuel contributions to atmospheric CO 2 concentrations. For each of the stations we calculate mean midday concentration signals with standard deviation for each month and source. We also calculate the covariance of the signal due to NEE inside CA with each of the other signals to quantify how much of the signal from NEE inside CA might be readily separable from the other signals. On the basis of these predictions, we identify new observing stations and a measurement protocol that, in combination with existing stations, would provide data to estimate NEE within CA. Although beyond the scope of this project, future work should estimate the uncertainties in estimating California's NEE that would be obtained using atmospheric concentration data from the stations identified herein. Carbon dioxide (CO 2 ) is a greenhouse gas (GHG) that is emitted by fossil fuel combustion for electricity production, transportation, industry, and other human uses. Globally, roughly half of the CO 2 emitted by fossil fuel combustion remains in the atmosphere, leading to sustained increases in atmospheric CO 2 concentrations. In-state electricity generation accounts for about 16% of California's anthropogenic CO 2 emissions. Keywords1 Because these emissions contribute to human-induced climate change, the California Energy Commission (Energy Commission) has identified the study of CO 2 and other GHGs as a priority area for research, with a particular focus on identifying CO 2 sources. Future cost and production strategies for electricity generation may be affected by economic and policy responses to global warming. Therefore, it will be important to determine the contribution of fossil fuel combustion and other sources of CO 2 exchange to atmospheric CO 2 levels.Cu...

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