Extension of the GAINS model to include short-lived climate forcers

Heyes, C. ORCID: https://orcid.org/0000-0001-5254-493X, Klimont, Z. ORCID: https://orcid.org/0000-0003-2630-198X, Wagner, F. ORCID: https://orcid.org/0000-0003-3429-2374, & Amann, M. ORCID: https://orcid.org/0000-0002-1963-0972 (2011). Extension of the GAINS model to include short-lived climate forcers. IIASA Report. IIASA, Laxenburg, Austria

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Abstract

This paper presents a first implementation of a new module to calculate the impacts of emission reductions of air pollutants on radiative forcing into IIASA’s GAINS (Greenhouse gas – Air pollution Interactions and Synergies) model. The approach extends the multi-pollutant/multi-effect approach of the GAINS model that has been used for air pollution impacts (i.e., human health and ecosystems impacts) to also consider impacts on near-term climate change from emissions of five short-lived substances.
For the initial implementation presented in this report source-receptor relationships have been developed that quantify the impacts of reductions of the various emission substances in each European country on instantaneous radiative forcing, calculated over the northern Hemisphere, the EMEP model domain, the Arctic and Alpine glaciers. These source-receptor relationships have been derived from calculations of the EMEP Eulerian atmospheric dispersion model, and employed normalized radiative forcing in each grid cell as estimated by CICERO.
The GAINS optimization module has been extended such that (a) radiative forcing for different target regions resulting from emission reductions that are optimized for health and environmental impacts of air pollutants can be calculated, (b) radiative forcing can be introduced as a separate constraint in the optimization (replacing targets for health and environmental impacts of air pollutants), and (c) combined strategies that meet constraints on radiative forcing as well as on health and environmental impacts at least costs can be identified. A sample of initial calculations is presented in this report, illustrating the relations between different environmental targets and radiative forcing. It turns out that in general cost-effective improvements of health impacts from PM2.5 and of acidification will increase radiative forcing by up to 150-200 mWm-2 in the EMEP region. In contrast, improvements in eutrophication will hardly affect radiative forcing. Furthermore, there are cheap ways to avoid some of the trade-offs between health effect and radiative forcing targets.
This initial analysis focuses on instantaneous radiative forcing over the EMEP domain. Input data and optimization routines have also been developed for carbon deposition on the Arctic and on Alpine glaciers. Analysis of the impacts of alternative emission control scenarios on these receptor regions, and optimization for such targets, will require additional work.
It needs to be emphasized that the current analysis is based on an initial data set of the impacts of radiative forcing, which only considers the direct effects of aerosols on radiative forcing. It does not include indirect effects of aerosols (for which an accurate quantification is burdened with significant uncertainties), and ignores changes in radiative forcing that result from changes in ozone burdens in the atmosphere caused by cuts of NOx and VOC emissions.

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