Climate Forcing by Aerosols--a Hazy Picture

Anderson, Theodore L.; Charlson, Robert J.; Schwartz, Stephen E.; Knutti, Reto; Boucher, Oliviér; Rodhe, Henning; Heintzenberg, Jost

doi:10.1126/science.1084777

Cited by 337 publications

(217 citation statements)

References 16 publications

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“…If taken at face value, the largest of these estimates would imply that the magnitude of the AIE is larger than estimates of the total forcing from greenhouse gases plus natural causes of about +2.7 Wm −2 (IPCC 2001;Boucher and Haywood, 2001). However, a total negative (natural plus greenhouse gases plus aerosols) forcing would not be consistent with the observed changes of temperature (Knutti et al, 2002;Anderson et al, 2003). So this might indicate these estimates are too large.…”

Section: Introductionmentioning

confidence: 65%

Examination of the aerosol indirect effect under contrasting environments during the ACE-2 experiment

et al. 2007

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Abstract. The Active Tracer High-resolution Atmospheric Model (ATHAM) has been adopted to examine the aerosol indirect effect in contrasting clean and polluted cloudy boundary layers during the Second Aerosol Characterization Experiment (ACE-2). Model results are in good agreement with available in-situ observations, which provides confidence in the results of ATHAM.Sensitivity tests have been conducted to examine the response of the cloud fraction (CF), cloud liquid water path (LWP), and cloud optical depth (COD) to changes in aerosols in the clean and polluted cases. It is shown for two cases that CF and LWP would decrease or remain nearly constant with an increase in aerosols, a result which shows that the second aerosol indirect effect is positive or negligibly small in these cases. Further investigation indicates that the background meteorological conditions play a critical role in the response of CF and LWP to aerosols. When large-scale subsidence is weak as in the clean case, the dry overlying air above the cloud is more efficiently entrained into the cloud, and in so doing, removes cloud water more efficiently, and results in lower CF and LWP when aerosol burden increases. However, when the large-scale subsidence is strong as in the polluted case, the growth of the cloud top is suppressed and the entrainment drying makes no significant difference when aerosol burden increases. Therefore, the CF and LWP remain nearly constant.In both the clean and polluted cases, the COD tends to increase with aerosols, and the total aerosol indirect effect (AIE) is negative even when the CF and LWP decrease with an increase in aerosols. Therefore, the first AIE dominates the response of the cloud to aerosols.

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Section: Introductionmentioning

confidence: 65%

Examination of the aerosol indirect effect under contrasting environments during the ACE-2 experiment

et al. 2007

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“…The aerosol influence on the earth's radiation budget is better understood now than it was a few years ago, but it still remains the dominant uncertainty in climate change scenarios (IPCC 2007;Anderson et al 2003). Several factors make identifying and quantifying aerosol effects on climate challenging (e.g., Menon 2004), and a substantial amount of literature on various aerosol effects now exists (see Menon 2004 for a review).…”

Section: Introductionmentioning

confidence: 99%

Absorbing Aerosols and Summer Monsoon Evolution over South Asia: An Observational Portrayal

2008

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The South Asian haze builds up from December to May, is mostly of anthropogenic origin, and absorbs part of the solar radiation. The influence of interannual variations of absorbing aerosols over the IndoGangetic Plain in May on the Indian summer monsoon is characterized by means of an observational analysis. Insight into how the aerosol impact is generated is also provided.It is shown that anomalous aerosol loading in late spring leads to remarkable and large-scale variations in the monsoon evolution. Excessive aerosols in May lead to reduced cloud amount and precipitation, increased surface shortwave radiation, and land surface warming. The June (and July) monsoon anomaly associated with excessive May aerosols is of opposite sign over much of the subcontinent (although with a different pattern) with respect to May. The monsoon strengthens in June (and July).The analysis suggests that the significant large-scale aerosol influence on monsoon circulation and hydroclimate is mediated by the heating of the land surface, pursuant to reduced cloudiness and precipitation in May. The finding of the significant role of the land surface in the realization of the aerosol impact is somewhat novel.

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“…The extent of this effect, known as 'aerosol indirect radiative forcing' , remains largely unknown. But it may offset greenhouse-gas warming even more than the aerosol direct radiative forcing 6 .…”

Section: Years Agomentioning

confidence: 99%

Multiple moulds

Goffeau

2005

Nature

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Climate Forcing by Aerosols--a Hazy Picture

Cited by 337 publications

References 16 publications

Examination of the aerosol indirect effect under contrasting environments during the ACE-2 experiment

Examination of the aerosol indirect effect under contrasting environments during the ACE-2 experiment

Absorbing Aerosols and Summer Monsoon Evolution over South Asia: An Observational Portrayal

Multiple moulds

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