emissions) Simple box models What is the GMST Can incorporate As above; neglects possible Boucher and Reddy, 2008; response to different multiple time scales dependence of GMST response to Held et al., 2010; RF scenarios? to estimate transient the spatial distribution of RF and Pierrehumbert, 2014; and steady-state thus is unlikely to approximate well Shindell et al., 2012. GMST changes for a the response to short-lived air variety of scenarios pollutants. Adjoint methods in a Which emissions Receptor-oriented Assumes linear system; by design Henze et al. 2012. GCTM (species, region, framework allows targets a single quantity sector) contribute to attribution to (‘receptor’). RF by a particular multiple factors in a atmospheric single simulation; constituent complementary to (regional, global)? forward modeling source attributions Methods applied to study climate impacts on air pollution Observed relationships How does air Observational Does not directly provide Bloomer et al., 2009; between chemical and pollution respond to constraints on information on how climate will Dawson et al. 2014; Jacob meteorological changing weather? models change, and may not correctly and Winner, 2009; variables identify the underlying drivers of Rasmussen et al., 2012; the correlation. Tai et al., 2010, 2012a. Statistical downscaling How will air Can be applied to a Assumes stationarity in the air Holloway et al., 2008; Tai using observed pollution respond to large suite of GCM pollutant response to the projected et al., 2012b. relationships (above) changes in regional physical climate meteorological variable. and climate change or global climate? change simulations projections (or their emulators) CTMs driven by How does air Develops Changes in air pollutants do not Section 4 of Jacob and perturbed pollution respond to understanding feed back on the climate system. Winner, 2009; Rasmussen meteorological changes in a of air pollutant et al., 2013; Steiner et al., variables meteorological response to changes 2006. driver? in a single factor; helps diagnose responses in more complex models Global CTM driven by How do changes in Sensitivity As above, plus often limited to a Jacob and Winner, 2009; meteorology from a climate alter air simulations separate few years of meteorology from the West et al., 2013; Wu et
emissions) Simple box models What is the GMST response to different RF scenarios? Can incorporate multiple time scales to estimate transient and steady-state GMST changes for a variety of scenarios As above; neglects possible dependence of GMST response to the spatial distribution of RF and thus is unlikely to approximate well the response to short-lived air pollutants. Boucher and Reddy, 2008; Held et al., 2010; Pierrehumbert, 2014; Shindell et al., 2012. Adjoint methods in a GCTM Which emissions (species, region, sector) contribute to RF by a particular atmospheric constituent (regional, global)? Receptor-oriented framework allows attribution to multiple factors in a single simulation; complementary to forward modeling source attributions Assumes linear system; by design targets a single quantity (‘receptor’). Henze et al. 2012. Methods applied to study climate impacts on air pollution Observed relationships between chemical and meteorological variables How does air pollution respond to changing weather? Observational constraints on models Does not directly provide information on how climate will change, and may not correctly identify the underlying drivers of the correlation. Bloomer et al., 2009; Dawson et al. 2014; Jacob and Winner, 2009; Rasmussen et al., 2012; Tai et al., 2010, 2012a. Statistical downscaling using observed relationships (above) and climate change projections How will air pollution respond to changes in regional or global climate? Can be applied to a large suite of GCM physical climate change simulations (or their emulators) Assumes stationarity in the air pollutant response to the projected meteorological variable. Holloway et al., 2008; Tai et al., 2012b. CTMs driven by perturbed meteorological variables How does air pollution respond to changes in a meteorological driver? Develops understanding of air pollutant response to changes in a single factor; helps diagnose responses in more complex models Changes in air pollutants do not feed back on the climate system. Section 4 of Jacob and Winner, 2009; Rasmussen et al., 2013; Steiner et al., 2006. Global CTM driven by meteorology from a How do changes in climate alter air Sensitivity simulations separate As above, plus often limited to a few years of meteorology from the Jacob and Winner, 2009; West et al., 2013; Wu et
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