2014 Progress Report: Source Attribution of Radiative Forcing in Chemical Transport Models
EPA Grant Number:
Source Attribution of Radiative Forcing in Chemical Transport Models
Henze, Daven K
University of Colorado at Boulder
EPA Project Officer:
June 1, 2012 through
May 31, 2014
(Extended to May 31, 2016)
Project Period Covered by this Report:
June 1, 2014 through May 31,2015
Source Attribution of Radiative Forcing in Chemical Transport (2011)
Global Climate Change
Air Quality and Air Toxics
The project objective is to account for the radiative forcing impacts of aerosols and tropospheric ozone (O3) from changes to their precursor emissions owing to air quality and greenhouse gas policies. This will be accomplished through the following research tasks:
Quantify the impacts of emissions from each sector, in each model grid cell, on the global and regional radiative forcing of tropospheric O3 and aerosols.
Assess the radiative forcing consequences of emissions scenarios designed to target combinations of aerosol and greenhouse gas reductions.
The third year of this project has focused on advancing our estimates of aerosol radiative source attribution in two major ways. Our initial work (Henze et al., 2012) included the direct aerosol radiative forcing. This last year, we have included indirect and semi-direct e ffects, as well as contributions from the albedo feedback of black carbon deposited on snow and ice. This is achieved through the application of scaling factors to account for indirect and semi-direct forcing. These scaling factors draw from multi-model comparisons such as ACCMIP and the 5th IPCC report. To account for the contribution of BC emissions to the radiative forcing of BC deposition on snow and ice, we first perform an additional adjoint model calculation to estimate the contribution of emissions of BC in each grid cell to BC deposited on snow and ice. These results are then used to spatially distribute the global mean estimated snow/ice albedo radiative forcing of 0.15 Wm-2. In addition, while our first study focused on the impact of global radiative forcing, now we have considered regional radiative forcing, and combined these with absolute regional temperature potentials (ARTPs) derived from climate model simulations by Shindell (2012) to estimate the changes in temperature across four latitudinal bands with associated aerosol precursor emissions.
These updates to our attribution method have been applied in a case study estimating the climate impacts of carbonaceous aerosol from cookstoves (Lacey and Henze, submitted). Cookstove use is globally one of the largest unregulated anthropogenic sources of primary carbonaceous aerosol. While reducing cookstove emissions through national-scale mitigation e fforts has clear benefi ts for improving indoor and ambient air quality, and signi cant climate benefi ts from reduced green-house gas emissions, climate impacts associated with reductions to co-emitted black (BC) and organic carbonaceous (OC) aerosol are not well characterized. Here we attribute direct, indirect, semi-direct, and snow/ice albedo radiative forcing and associated zonal surface temperature changes to national-scale carbonaceous aerosol cookstove emissions using a new combination of adjoint sensitivity modeling and climate-model parameterizations. Bounds are placed on these estimates, drawing from current literature ranges for aerosol radiative forcing along with a range of solid fuel emissions characterizations. We estimate a range of 0.16 K warming to 0.28 K cooling with a central estimate of 0.06 K cooling from the global removal of cookstove aerosol emissions. At the national scale, countries' climate impacts range from net warming (e.g., Mexico and Brazil) to net cooling, although the range of estimated impacts for all countries span zero given uncertainties in radiative forcing estimates and fuel characterization. We identify similarities and di fferences in the sets of countries with the highest emissions and largest cookstove temperature impacts (China, India, Nigeria, Pakistan, Bangladesh and Nepal), those with the largest temperature impact per carbon emitted (Kazakhstan, Estonia, and Mongolia), and those that would provide the most efficient cooling from a switch to fuel with a lower BC emission factor (Kazakhstan, Estonia, and Latvia). The results presented here thus provide valuable information for climate impact assessments across a wide range of cookstove initiatives.
The remaining efforts will focus on combining our source attribution of aerosol impacts with: (1) source attribution of climate impacts from both long-lived greenhouse gases as well as tropospheric O3 from Bowman and Henze (2012), and (2) source attribution of PM2.5 health impacts, from Lee et al. (2015). This will allow us to most completely evaluate the climate and health impacts of air quality initiatives, such as those focused on reducing emissions from cookstoves or sources of CH4.
Bowman K, Henze DK. Attribution of direct ozone radiative forcing to spatially resolved emissions. Geophysical Research Letters. 2012 Nov 28;39(22).
Henze, D.K., D.T. Shindell, F. Akhtar, R.D.J. Spurr, R.W. Pinder, D. Loughlin, M. Kopacz, K. Singh, and C. Shim, 2012: Spatially refined aerosol direct radiative forcing efficiencies. Environ. Sci. Technol., 46, 9511-9518, doi:10.1021/es301993
Lee CJ, Martin RV, Henze DK, Brauer M, Cohen A, Donkelaar AV. Response of global particulate-matter-related mortality to changes in local precursor emissions. Environmental Sci. Technol. 2015 Mar 24;49(7):4335-44.
Shindell, D., J.C.I. Kuylenstierna, E. Vignati, R. van Dingenen, M. Amann, Z. Klimont, S.C. Anenberg, N. Muller, G. Janssens-Maenhout, F. Raes, J. Schwartz, G. Faluvegi, L. Pozzoli, K. Kupiainen, L. Höglund-Isaksson, L. Emberson, D. Streets, V. Ramanathan, K. Hicks, N.T.K. Oanh, G. Milly, M. Williams, V. Demkine, and D. Fowler, 2012: Simultaneously mitigating near-term climate change and improving human health and food security. Science, 335, 183-189, doi:10.1126/science.1210026
on this Report
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Adjoint sensitivity, environmental policy, air quality regulations, fine particulate matter, climate change, remote sensing
Progress and Final Reports:
2012 Progress Report
2013 Progress Report