Connecting regional aerosol emissions reductions to local and remote precipitation responses

Westervelt, Daniel M.; Conley, Andrew; Fiore, Arlene M.; Lamarque, Jean‐François; Shindell, D. T.; Previdi, Michael; Mascioli, N. R.; Faluvegi, G.; Correa, Gustavo; Horowitz, Larry W.

doi:10.5194/acp-2018-516

Cited by 11 publications

(14 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, NTCF mitigation generally increases precipitation in most world regions (although, in some regions, this is a smaller decrease) but the signal is less robust than that for surface temperature. Furthermore, in agreement with prior studies (Levy et al, 2013;Westervelt et al, 2017;Zhao et al, 2018;Westervelt et al, 2018;Scannell et al, submitted), precipitation increases in several monsoon regions, including east Africa, south Asia, and east Asia.…”

Section: Regional Climate and Air Quality Trendssupporting

confidence: 92%

Climate and air quality impacts due to mitigation of non-methane near-term climate forcers

Allen¹,

Turnock²,

Nabat³

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. Over the next few decades, policies that optimally address both climate change and air quality are essential. Although targeting near-term climate forcers (NTCFs), defined here as aerosols, tropospheric ozone and precursor gases (but not methane), should improve air quality, NTCF reductions will also impact climate. How future policies affect the abundance of NTCFs and their impact on climate and air quality remains uncertain. Here, we quantify the 2015&#8211;2055 climate and air quality effects of non-methane NTCFs using state-of-the-art chemistry-climate model simulations conducted for the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP). Simulations are driven by two future scenarios featuring similar increases in greenhouse gases (GHGs) but with <q>weak</q> versus <q>strong</q> levels of air quality control measures. Unsurprisingly, we find significant improvements in air quality under NTCF mitigation (strong versus weak air quality controls). Surface ozone (O3) and fine particulate matter (PM2.5) decrease by &#8722;15&#8201;% and &#8722;25&#8201;%, respectively, over global land surfaces, with larger reductions in some regions including south and southeast Asia. Non-methane NTCF mitigation, however, leads to additional climate change due to the removal of aerosol which causes a net warming effect, including global mean surface temperature and precipitation increases of 0.24&#8201;K and 1.1&#8201;%, respectively, with similar increases in extreme weather indices. Regionally, the largest warming and wetting trends occur over Asia, including central and north Asia (0.56&#8201;K and 2.1&#8201;%), south Asia (0.48&#8201;K and 4.6&#8201;%) and east Asia (0.44&#8201;K and 4.7&#8201;%). Relatively large warming and wetting of the Arctic also occurs at 0.41&#8201;K and 2.1&#8201;%, respectively. Similar surface warming occurs in model simulations with aerosol-only mitigation, implying weak cooling due to ozone reductions. Our findings suggest that future policies that aggressively target non-methane NTCF reductions will improve air quality, but will lead to additional surface warming, particularly in Asia and the Arctic. Policies that address other NTCFs including methane, as well as carbon dioxide emissions, must also be adopted to meet mitigation goals.

show abstract

Section: Regional Climate and Air Quality Trendssupporting

confidence: 92%

Climate and air quality impacts due to mitigation of non-methane near-term climate forcers

Allen¹,

Turnock²,

Nabat³

et al. 2020

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The anticyclonic anomaly in the North Atlantic also causes Europe to be anomalously dry relative to 1979-1993, while the Mediterranean is anomalously wet (Figure 3(b)). This positive North-Atlantic-Oscillation-like response is consistent with the responses seen by Allen and Sherwood (2011) and Westervelt et al (2018) in response to increases in global aerosols. Note, however, that Westervelt et al (2018) identified a degree of model-sensitivity in the North Atlantic response to global aerosols, and identified an increase in Mediterranean precipitation that we do not see here.…”

Section: Resultssupporting

confidence: 84%

Mechanisms for a remote response to Asian aerosol emissions in boreal winter

Wilcox¹,

Dunstone²,

Lewinschal³

et al. 2018

Preprint

View full text Add to dashboard Cite

Abstract. Asian emissions of anthropogenic aerosols have increased rapidly since 1980, with half of the increase since the pre-industrial era occurring in this period. Transient experiments with the HadGEM3-GC2 coupled model were designed to isolate the impact of Asian aerosols on global climate. In boreal winter, it is found that this increase has resulted in local circulation changes, which in turn have driven increases in temperature and decreases in precipitation over China, alongside an intensification of the offshore monsoon flow. Over India, the opposite response is found, with decreasing temperatures and increasing precipitation. The dominant feature of the local circulation changes is an increase in low-level convergence, ascent, and precipitation over the Maritime continent, which forms part of a tropical-Pacific-wide La-Nina-like response. HadGEM3-GC2 also simulates pronounced far-field responses. A decreased meridional temperature gradient in the North Pacific leads to a positive-Pacific-North-American circulation pattern, with associated temperature anomalies over the North Pacific and North America. An anomalous anticyclonic circulation over the North Atlantic, and an anomalous cyclonic circulation over the Mediterranean drive advection of cold air into Europe, causing cooling in this region. Using a steady-state primitive equation model, LUMA, we demonstrate that these far-field midlatitude response arise primarily as a result of Rossby waves generated over China, rather than in the Equatorial Pacific.

show abstract

“…More recently, however, most of the SST variance over the Atlantic was found to be radiatively forced also in other models Murphy et al, 2017), with a distinct contribution of anthropogenic aerosols on both temporal and spatial variability. Note that aerosol impact on SSTs elsewhere, possibly including decadal El Niño-Southern Oscillation variability, has also been suggested (e.g., Sutton & Hodson, 2007;Westervelt et al, 2018).…”

Section: Geophysical Research Lettersmentioning

confidence: 97%

Contrasting the Effects of the 1850–1975 Increase in Sulphate Aerosols from North America and Europe on the Atlantic in the CESM

Undorf

Bollasina

Booth

et al. 2018

Geophysical Research Letters

View full text Add to dashboard Cite

The extent and mechanisms of the Atlantic response to the historical (1850–1975) increase of sulphate aerosol emissions from North America and Europe as simulated in eight‐member ensemble experiments with the coupled Community Earth System Model (CESM1)‐Community Atmosphere Model version 5.3 are contrasted. The results show that aerosols from either source cause a long‐term cooling of North Atlantic sea surface temperatures, with the patterns a combination of atmospheric aerosol effects and an aerosol‐induced strengthening of the Atlantic Meridional Overturning Circulation. The response to North American emissions is larger since prevailing winds cause wider aerosol spread over the Atlantic, collocated with climatological cloud cover. The Intertropical Convergence Zone shifts southward affecting tropical precipitation globally. The simulated (multi)decadal components of sea surface temperature and Atlantic Meridional Overturning Circulation variability are furthermore primarily externally forced. The analysis provides novel insights into the mechanisms of aerosol impact on the Atlantic. It suggests that projected further emission reductions will lead to opposite changes.

show abstract

Connecting regional aerosol emissions reductions to local and remote precipitation responses

Abstract: Abstract. The unintended climatic implications of aerosol and precursor emission reductions implemented to protect public health are poorly understood. We investigate the precipitation response to regional changes in aerosol emissions using three 15

Cited by 11 publications

References 41 publications

Climate and air quality impacts due to mitigation of non-methane near-term climate forcers

Climate and air quality impacts due to mitigation of non-methane near-term climate forcers

Mechanisms for a remote response to Asian aerosol emissions in boreal winter

Contrasting the Effects of the 1850–1975 Increase in Sulphate Aerosols from North America and Europe on the Atlantic in the CESM

Contact Info

Product

Resources

About