MuQuantification of high-resolution, bottom-up fossil fuel CO2 emissions at the global, national and urban landscape domains

Overview

Among the global annual net carbon fluxes between the land, ocean and atmosphere, the CO2 flux resulting from the combustion of fossil fuels, the dominant driver of anthropogenic climate change, is the largest. Atmospheric CO2 inversion/assimilation and carbon budget studies rely on an accurate quantification of fossil fuel CO2 emissions to understand where, when and how carbon is exchanged with the terrestrial biosphere and ocean surface. It has been shown that errors in either the location or timing of fossil fuel CO2 fluxes can be aliased into the remaining flux components of carbon inversion studies. Accurate quantification of the fossil fuel CO2 flux is not only critical for improved understanding of the global carbon cycle but is equally important to climate policy. Cities, provinces, and countries use fossil fuel CO2 flux quantification as a means to baseline their emissions for reporting purposes, better understand their options for emissions reductions, and assess progress on reductions. With the rise of carbon markets, fossil fuel CO2 emissions quantification may be called on to act as verification of traded emissions or policy measures. Indeed Monitoring, Reporting, and Verification (MRV) has emerged as a distinct need within the international climate change policy community for which better independent quantification of fossil fuel CO2 emissions figure prominently.

To meet both science and policy needs, FFCO2 estimation must be resolved at space and time scales that are commensurate with new and evolving atmospheric measurement systems (e.g. satellite-based, 14CO2 measurements) and sub-national policy needs. I will present research that has quantified FFCO2 emissions at high space/time resolution over three domains: global, national, and urban. These three domains have availed of different techniques and data sources and are forming a critical component of a emerging carbon monitoring system with global capabilities. They are now being merged into a single “nested” data product.

Global: The Fossil Fuel Data Assimilation System (FFDAS) is a global FFCO2 estimation system that has quantified emissions for the globe at the 0.1 degree/hourly scale for every year from 1997 to 2011 (http://hpcg.purdue.edu/FFDAS/index.php). Methodologically, the FFDAS estimates fossil fuel CO2 emissions by constraining elements of the Kaya identity at the gridcell level with national statistics on fossil fuel CO2 emissions, remotely sensed nighttime lights, population data, and information on the world's power plants [Rayner et al., 2010; Asefi-Najafabady et al., 2014]. As an assimilation system, FFDAS generates both an estimate of emissions at the gridcell level and an accompanying posterior uncertainty estimate. FFDAS is currently being used by global carbon assimilation systems aimed at better understanding the global carbon cycle. It also holds potential as both a verification and mitigation guide to international policymaking efforts.

US National: The Vulcan Project has estimated US fossil fuel CO2 emissions at the hourly/sub-county scales (placed on a regular 10 km x 10 km grid) for the year 2002 timespan (currently generating 2002-2011 mltiyear data product) [Gurney et al., 2009]. Vulcan is built from a wide variety of “bottom-up” observational data streams including EPA air pollutant emissions reporting, traffic monitoring, energy statistics, and census data. Vulcan also relies on a series of modeling assumptions and constructs to interpolate in space, time and transform non-CO2 reporting into an estimate of CO2 combustion emissions. Vulcan is being used by geoscientists, social scientists, geographers, economists, and policy analysts to understand the North American Carbon Cycle, energy intensities, and social drivers of carbon emissions.

Urban: The Hestia Project estimates FFCO2 emissions at the spatial scale of individual buildings and street segments and the hourly temporal scale across entire urban landscapes [Gurney et al., 2012]. This leverages from the Vulcan constraint at the county level and focuses on two important sectors: buildings and onroad transportation. To estimate buildings, allocation of county/fuel/sector emissions are performed through the use of a building energy model and local parcel assessor data. Onroad transportation places the Vulcan county-level emissions onto roadways using a road atlas and traffic monitoring data. A complete data product has been built for the cities of Indianapolis, IN and Salt Lake City, UT with work underway in the entire LA Basin, CA and Phoenix, AZ. The effort in Indianapolis is now part of the “INFLUX” experiment and the Megacity Carbon project in Los Angeles. These experiments are attempting to use the Hestia result in conjunction with atmospheric measurements and atmospheric transport modeling to converge on a top-down/bottom-up assessment of greenhouse gas emissions. A key benefit of the approach taken in this study is the tracking and archiving of fuel and process-level detail (eg. combustion process, other pollutants), allowing for a more thorough understanding and analysis of energy throughputs in the urban environment. Quantification of fossil fuel emissions, however, is one piece in a larger conception of cities as complex dynamic socio-technological systems and the Hestia effort is at the very beginning stages of connecting to the large community of research approaching cities from other perspectives and utilizing other tools.

References

Gurney, K.R., D. Mendoza, Y. Zhou, M Fischer, S. de la Rue du Can, S. Geethakumar, C. Miller (2009) The Vulcan Project: High resolution fossil fuel combustion CO2 emissions fluxes for the United States, Environ. Sci. Technol., 43(14), 5535-5541, doi:10.1021/es900806c.

Gurney, K.R., Razlivanov, I., Song, Y. Zhou, Y., Benes, B., M. Abdul-Massih (2012) Quantification of fossil fuel CO2 at the building/street scale for a large US city Environ. Sci. & Tech., 46, 12194-12202, dx.doi.org/10.1021/es3011282

Asefi-Najafabady, S., P. J. Rayner, K.R. Gurney, A. McRobert, Y. Song, K. Coltin, C. Elvidge, K. Baugh (2014) A new global gridded dataset of CO2 emissions from fossil fuel combustion: Methodology, evaluation and analysis, accepted to J. Geophys. Res.

Rayner, P.J., M.R. Raupach, M. Paget, P. Peylin, E. Koffi (2010), A new global gridded data set of CO2 emissions from fossil fuel combustion: Methodology and evaluation, J. Geophys. Res., 115, D19306, doi:10.1029/2009JD013439