| 英文摘要: | Atmospheric aerosols are of significant environmental importance, due to their effects on air quality, as well as their ability to alter the planet’s radiative balance. Recent studies characterizing the effects of climate change on air quality and the broader distribution of aerosols in the atmosphere show significant, but inconsistent results, including the sign of the effect1, 2, 3. Using a suite of state-of-the-art climate models, we show that climate change is associated with a negative aerosol–climate feedback of −0.02 to −0.09 W m−2 K−1 for direct radiative effects, with much larger values likely for indirect radiative effects. This is related to an increase in most aerosol species, particularly over the tropics and Northern Hemisphere midlatitudes, largely due to a decrease in wet deposition associated with less large-scale precipitation over land. Although simulation of aerosol processes in global climate models possesses uncertainty, we conclude that climate change may increase aerosol burden and surface concentration, which may have implications for future air quality. The burden of atmospheric aerosols depends on several factors, including emissions, chemistry and weather patterns. Although emissions are the dominant factor determining ambient aerosol concentrations, multiple links between global climate change and aerosol concentrations exist. Future responses of the climate system to greenhouse gas (GHG) warming will lead to changes in the hydrologic cycle4 and atmospheric circulation5, 6, 7, 8, 9 that will subsequently affect air quality and the distribution of aerosols irrespective of changes in emissions. Projections of future climate change yield a global increase in precipitation, and local increases in precipitation are expected to simultaneously decrease aerosol burdens10, 11, 12. However, changes in the frequency/intensity of precipitation and storm tracks may offset any potential increases in wet removal associated with a global increase in precipitation12. Recent studies suggest that the warming associated with increasing GHGs may lead to an overall increase in the burden of soluble aerosols (for example, sulphate, black carbon)13, 14, 15, and this ‘climate penalty’ may impact a region’s ability to attain a specified air quality standard. In addition to its association with air quality, aerosols impact the radiative balance of the planet. Most aerosol species, such as sulphate, reflect solar radiation and alter cloud microphysical properties, which enhances cloud albedo and lifetime. Changes in aerosols due to future climate warming will therefore affect the planetary energy balance, constituting a feedback loop16, 17. With respect to both anthropogenic and natural (sea salt, dust) aerosols, significant positive and negative feedbacks have been found16, 18, 19, 20. Table 1 shows the response of several aerosol species to climate change, as simulated by climate models from the Atmospheric Chemistry and Climate Model Intercomparison Project (ACCMIP; refs 21,22). Responses are based on the difference between two time-slice simulations representing climate in the year 2000 and 2100 (based on Representative Concentration Pathway 8.5, RCP8.5), both with identical emissions from year 2000. Also included are similar experiments with the Community Atmosphere Model versions 4 and 5 (CAM4/5; Supplementary Methods). Models show that climate change associated with GHG-induced global warming will result in significantly elevated surface concentrations of all primary anthropogenic aerosol species (SO4, BC and POM). For example, the average increase in surface sulphate concentration is 11.4%, with a range of 1.7%–17.7%. Similarly, the average increase in black carbon (primary organic matter) surface concentration is 10.5% (6.8%), with a range of 0.3%–30.2% (0.1%–15.3%). Models also show significant increases in primary anthropogenic aerosol burden, particularly for sulphate, where the mean increase is 12.5%, with a range of 0.6%–33.1%. Increases in BC and POM burden also exist (except in GISS-E2-R-p3), with several models yielding more than a 20% increase. Fine particulate matter (PM2.5) also shows increases. Thus, climate change associated with GHG warming may result in enhanced anthropogenic aerosol burden and surface aerosol concentration.
| http://www.nature.com/nclimate/journal/v6/n3/full/nclimate2827.html
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