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Anthropogenic influence on climate through changes in aerosol emissions from air pollution and land use change
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
2017 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Particulate matter suspended in air (i.e. aerosol particles) exerts a substantial influence on the climate of our planet and is responsible for causing severe public health problems in many regions across the globe. Human activities have altered the natural and anthropogenic emissions of aerosol particles through direct emissions or indirectly by modifying natural sources. The climate effects of the latter have been largely overlooked. Humans have dramatically altered the land surface of the planet causing changes in natural aerosol emissions from vegetated areas. Regulation on anthropogenic and natural aerosol emissions have the potential to affect the climate on regional to global scales. Furthermore, the regional climate effects of aerosol particles could potentially be very different than the ones caused by other climate forcers (e.g. well mixed greenhouse gases). The main objective of this work was to investigate the climatic effects of land use and air pollution via aerosol changes.

Using numerical model simulations it was found that land use changes in the past millennium have likely caused a positive radiative forcing via aerosol climate interactions. The forcing is an order of magnitude smaller and has an opposite sign than the radiative forcing caused by direct aerosol emissions changes from other human activities. The results also indicate that future reductions of fossil fuel aerosols via air quality regulations may lead to an additional warming of the planet by mid-21st century and could also cause an important Arctic amplification of the warming. In addition, the mean position of the intertropical convergence zone and the Asian monsoon appear to be sensitive to aerosol emission reductions from air quality regulations. For these reasons, climate mitigation policies should take into consideration aerosol air pollution, which has not received sufficient attention in the past.

Ort, förlag, år, upplaga, sidor
Stockholm: Department of Environmental Science and Analytical Chemistry, Stockholm University , 2017.
Nyckelord [en]
Climate change, Air quality, Land use, General circulation, Atmosphere-Ocean interactions, Aerosol climate effects, Earth system modelling
Nationell ämneskategori
Klimatforskning Meteorologi och atmosfärforskning Miljövetenskap Oceanografi, hydrologi och vattenresurser
Forskningsämne
tillämpad miljövetenskap
Identifikatorer
URN: urn:nbn:se:su:diva-137077ISBN: 978-91-7649-650-3 (tryckt)ISBN: 978-91-7649-651-0 (tryckt)OAI: oai:DiVA.org:su-137077DiVA, id: diva2:1059239
Disputation
2017-02-17, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 13:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2017-01-25 Skapad: 2016-12-22 Senast uppdaterad: 2018-01-13Bibliografiskt granskad
Delarbeten
1. Global emissions of terpenoid VOCs from terrestrial vegetation in the last millennium
Öppna denna publikation i ny flik eller fönster >>Global emissions of terpenoid VOCs from terrestrial vegetation in the last millennium
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2014 (Engelska)Ingår i: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 119, nr 11, s. 6867-6885Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We investigated the millennial variability (1000 A.D.-2000 A.D.) of global biogenic volatile organic compound (BVOC) emissions by using two independent numerical models: The Model of Emissions of Gases and Aerosols from Nature (MEGAN), for isoprene, monoterpene, and sesquiterpene, and Lund-Potsdam-Jena-General Ecosystem Simulator (LPJ-GUESS), for isoprene and monoterpenes. We found the millennial trends of global isoprene emissions to be mostly affected by land cover and atmospheric carbon dioxide changes, whereas monoterpene and sesquiterpene emission trends were dominated by temperature change. Isoprene emissions declined substantially in regions with large and rapid land cover change. In addition, isoprene emission sensitivity to drought proved to have significant short-term global effects. By the end of the past millennium MEGAN isoprene emissions were 634 TgC yr-1 (13% and 19% less than during 1750-1850 and 1000-1200, respectively), and LPJ-GUESS emissions were 323 TgC yr-1(15% and 20% less than during 1750-1850 and 1000-1200, respectively). Monoterpene emissions were 89 TgC yr-1(10% and 6% higher than during 1750-1850 and 1000-1200, respectively) in MEGAN, and 24 TgC yr-1 (2% higher and 5% less than during 1750-1850 and 1000-1200, respectively) in LPJ-GUESS. MEGAN sesquiterpene emissions were 36 TgC yr-1(10% and 4% higher than during 1750-1850 and 1000-1200, respectively). Although both models capture similar emission trends, the magnitude of the emissions are different. This highlights the importance of building better constraints on VOC emissions from terrestrial vegetation.

Nyckelord
VOC emissions, land cover, isoprene, monoterpene, sesquiterpene
Nationell ämneskategori
Geovetenskap och miljövetenskap
Forskningsämne
tillämpad miljövetenskap
Identifikatorer
urn:nbn:se:su:diva-106340 (URN)10.1002/2013JD021238 (DOI)000337974500038 ()
Anmärkning

AuthorCount:9;

Tillgänglig från: 2014-08-08 Skapad: 2014-08-04 Senast uppdaterad: 2019-12-12Bibliografiskt granskad
2. Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation
Öppna denna publikation i ny flik eller fönster >>Aerosol size distribution and radiative forcing response to anthropogenically driven historical changes in biogenic secondary organic aerosol formation
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2015 (Engelska)Ingår i: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 15, s. 2247-2268Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Emissions of biogenic volatile organic compounds (BVOCs) have changed in the past millennium due to changes in land use, temperature, and CO2 concentrations. Recent reconstructions of BVOC emissions have predicted that global isoprene emissions have decreased, while monoterpene and sesquiterpene emissions have increased; however, all three show regional variability due to competition between the various influencing factors. In this work, we use two modeled estimates of BVOC emissions from the years 1000 to 2000 to test the effect of anthropogenic changes to BVOC emissions on secondary organic aerosol (SOA) formation, global aerosol size distributions, and radiative effects using the GEOS-Chem-TOMAS (Goddard Earth Observing System; TwO-Moment Aerosol Sectional) global aerosol microphysics model. With anthropogenic emissions (e.g., SO2, NOx, primary aerosols) turned off and BVOC emissions changed from year 1000 to year 2000 values, decreases in the number concentration of particles of size Dp > 80 nm (N80) of > 25% in year 2000 relative to year 1000 were predicted in regions with extensive land-use changes since year 1000 which led to regional increases in the combined aerosol radiative effect (direct and indirect) of > 0.5 W m−2 in these regions. We test the sensitivity of our results to BVOC emissions inventory, SOA yields, and the presence of anthropogenic emissions; however, the qualitative response of the model to historic BVOC changes remains the same in all cases. Accounting for these uncertainties, we estimate millennial changes in BVOC emissions cause a global mean direct effect of between +0.022 and +0.163 W m−2 and the global mean cloud-albedo aerosol indirect effect of between −0.008 and −0.056 W m−2. This change in aerosols, and the associated radiative forcing, could be a largely overlooked and important anthropogenic aerosol effect on regional climates.

Nationell ämneskategori
Geovetenskap och miljövetenskap
Forskningsämne
tillämpad miljövetenskap
Identifikatorer
urn:nbn:se:su:diva-123191 (URN)10.5194/acp-15-2247-2015 (DOI)000350559700002 ()
Tillgänglig från: 2015-11-18 Skapad: 2015-11-18 Senast uppdaterad: 2017-12-01Bibliografiskt granskad
3. Amplification of Arctic warming by past air pollution reductions in Europe
Öppna denna publikation i ny flik eller fönster >>Amplification of Arctic warming by past air pollution reductions in Europe
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2016 (Engelska)Ingår i: Nature Geoscience, ISSN 1752-0894, E-ISSN 1752-0908, Vol. 9, nr 4, s. 277-+Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The Arctic region is warming considerably faster than the rest of the globe(1), with important consequences for the ecosystems(2) and human exploration of the region(3). However, the reasons behind this Arctic amplification are not entirely clear(4). As a result of measures to enhance air quality, anthropogenic emissions of particulate matter and its precursors have drastically decreased in parts of the Northern Hemisphere over the past three decades(5). Here we present simulations with an Earth system model with comprehensive aerosol physics and chemistry that show that the sulfate aerosol reductions in Europe since 1980 can potentially explain a significant fraction of Arctic warming over that period. Specifically, the Arctic region receives an additional 0.3Wm(-2) of energy, and warms by 0.5 degrees C on annual average in simulations with declining European sulfur emissions in line with historical observations, compared with a model simulation with fixed European emissions at 1980 levels. Arctic warming is amplified mainly in fall and winter, but the warming is initiated in summer by an increase in incoming solar radiation as well as an enhanced poleward oceanic and atmospheric heat transport. The simulated summertime energy surplus reduces sea-ice cover, which leads to a transfer of heat from the Arctic Ocean to the atmosphere. We conclude that air quality regulations in the Northern Hemisphere, the ocean and atmospheric circulation, and Arctic climate are inherently linked.

Nationell ämneskategori
Geovetenskap och miljövetenskap
Forskningsämne
tillämpad miljövetenskap
Identifikatorer
urn:nbn:se:su:diva-130127 (URN)10.1038/NGEO2673 (DOI)000373374100010 ()
Tillgänglig från: 2016-05-18 Skapad: 2016-05-09 Senast uppdaterad: 2019-12-12Bibliografiskt granskad
4. Future response of temperature and precipitation to reduced aerosol emissions as compared with increased greenhouse gas concentrations
Öppna denna publikation i ny flik eller fönster >>Future response of temperature and precipitation to reduced aerosol emissions as compared with increased greenhouse gas concentrations
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2017 (Engelska)Ingår i: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 30, nr 3, s. 939-954Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Experiments with a climate model (NorESM1) were performed to isolate the effects of aerosol particles and greenhouse gases on surface temperature and precipitation in simulations of future climate. The simulations show that by 2025-2049, a reduction of aerosol emissions from fossil fuels following a maximum technically feasible reduction (MFR) scenario could lead to a global and Arctic warming of 0.26 K and 0.84 K, respectively; as compared with a simulation with fixed aerosol emissions at the level of 2005. If fossil fuel emissions of aerosols follow a current legislation emissions (CLE) scenario, the NorESM1 model simulations yield a non-significant change in global and Arctic average surface temperature as compared with aerosol emissions fixed at year 2005. The corresponding greenhouse gas effect following the RCP4.5 emission scenario leads to a global and Arctic warming of 0.35 K and 0.94 K, respectively.

The model yields a marked annual average northward shift in the inter-tropical convergence zone with decreasing aerosol emissions and subsequent warming of the northern hemisphere. The shift is most pronounced in the MFR scenario but also visible in the CLE scenario. The modeled temperature response to a change in greenhouse gas concentrations is relatively symmetric between the hemispheres and there is no marked shift in the annual average position of the inter-tropical convergence zone. The strong reduction in aerosol emissions in MFR also leads to a net southward cross-hemispheric energy transport anomaly both in the atmosphere and ocean, and enhanced monsoon circulation in Southeast and East Asia causing an increase in precipitation over a large part of this region.

Nationell ämneskategori
Geovetenskap och miljövetenskap
Forskningsämne
tillämpad miljövetenskap
Identifikatorer
urn:nbn:se:su:diva-137076 (URN)10.1175/JCLI-D-16-0466.1 (DOI)000395512300007 ()
Tillgänglig från: 2016-12-22 Skapad: 2016-12-22 Senast uppdaterad: 2017-05-03Bibliografiskt granskad

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