Publications by year
2022
de Boer G, Young McCusker G, Sotiropoulou G, Gramlich Y, Browse J, Raut J-C (2022). Furthering Understanding of Aerosol–Cloud–Precipitation Interactions in the Arctic. Bulletin of the American Meteorological Society, 103(11), e2484-e2491.
Mitchell DM, Stone EJ, Andrews OD, Bamber JL, Bingham RJ, Browse J, Henry M, MacLeod DM, Morten JM, Sauter CA, et al (2022). The Bristol <scp>CMIP6</scp> Data Hackathon. Weather, 77(6), 218-221.
Song C, Becagli S, Beddows DCS, Brean J, Browse J, Dai Q, Dall'Osto M, Ferracci V, Harrison RM, Harris N, et al (2022). Understanding Sources and Drivers of Size-Resolved Aerosol in the High Arctic Islands of Svalbard Using a Receptor Model Coupled with Machine Learning.
Environ Sci Technol,
56(16), 11189-11198.
Abstract:
Understanding Sources and Drivers of Size-Resolved Aerosol in the High Arctic Islands of Svalbard Using a Receptor Model Coupled with Machine Learning.
Atmospheric aerosols are important drivers of Arctic climate change through aerosol-cloud-climate interactions. However, large uncertainties remain on the sources and processes controlling particle numbers in both fine and coarse modes. Here, we applied a receptor model and an explainable machine learning technique to understand the sources and drivers of particle numbers from 10 nm to 20 μm in Svalbard. Nucleation, biogenic, secondary, anthropogenic, mineral dust, sea salt and blowing snow aerosols and their major environmental drivers were identified. Our results show that the monthly variations in particles are highly size/source dependent and regulated by meteorology. Secondary and nucleation aerosols are the largest contributors to potential cloud condensation nuclei (CCN, particle number with a diameter larger than 40 nm as a proxy) in the Arctic. Nonlinear responses to temperature were found for biogenic, local dust particles and potential CCN, highlighting the importance of melting sea ice and snow. These results indicate that the aerosol factors will respond to rapid Arctic warming differently and in a nonlinear fashion.
Abstract.
Author URL.
2021
Sengupta K, Pringle K, Johnson JS, Reddington C, Browse J, Scott CE, Carslaw K (2021). A global model perturbed parameter ensemble study of secondary organic aerosol formation.
ATMOSPHERIC CHEMISTRY AND PHYSICS,
21(4), 2693-2723.
Author URL.
2020
Sengupta K, Pringle K, Johnson JS, Reddington C, Browse J, Scott CE, Carslaw K (2020). A global model perturbed parameter ensemble study of secondary organic aerosol formation. , 2020, 1-47.
Mulcahy JP, Johnson C, Jones CG, Povey AC, Scott CE, Sellar A, Turnock ST, Woodhouse MT, Abraham NL, Andrews MB, et al (2020). Description and evaluation of aerosol in UKESM1 and HadGEM3-GC3.1 CMIP6 historical simulations. , 2020, 1-59.
Mulcahy JP, Johnson C, Jones CG, Povey AC, Scott CE, Sellar A, Turnock ST, Woodhouse MT, Abraham NL, Andrews MB, et al (2020). Description and evaluation of aerosol in UKESM1 and HadGEM3-GC3.1 CMIP6 historical simulations.
Geoscientific Model Development,
13(12), 6383-6423.
Abstract:
Description and evaluation of aerosol in UKESM1 and HadGEM3-GC3.1 CMIP6 historical simulations
We document and evaluate the aerosol schemes as implemented in the physical and Earth system models, the Global Coupled 3.1 configuration of the Hadley Centre Global Environment Model version 3 (HadGEM3-GC3.1) and the United Kingdom Earth System Model (UKESM1), which are contributing to the sixth Coupled Model Intercomparison Project (CMIP6). The simulation of aerosols in the present-day period of the historical ensemble of these models is evaluated against a range of observations. Updates to the aerosol microphysics scheme are documented as well as differences in the aerosol representation between the physical and Earth system configurations. The additional Earth system interactions included in UKESM1 lead to differences in the emissions of natural aerosol sources such as dimethyl sulfide, mineral dust and organic aerosol and subsequent evolution of these species in the model. UKESM1 also includes a stratospheric'tropospheric chemistry scheme which is fully coupled to the aerosol scheme, while GC3.1 employs a simplified aerosol chemistry mechanism driven by prescribed monthly climatologies of the relevant oxidants. Overall, the simulated speciated aerosol mass concentrations compare reasonably well with observations. Both models capture the negative trend in sulfate aerosol concentrations over Europe and the eastern United States of America (US) although the models tend to underestimate sulfate concentrations in both regions. Interactive emissions of biogenic volatile organic compounds in UKESM1 lead to an improved agreement of organic aerosol over the US. Simulated dust burdens are similar in both models despite a 2-fold difference in dust emissions. Aerosol optical depth is biased low in dust source and outflow regions but performs well in other regions compared to a number of satellite and ground-based retrievals of aerosol optical depth. Simulated aerosol number concentrations are generally within a factor of 2 of the observations, with both models tending to overestimate number concentrations over remote ocean regions, apart from at high latitudes, and underestimate over Northern Hemisphere continents. Finally, a new primary marine organic aerosol source is implemented in UKESM1 for the first time. The impact of this new aerosol source is evaluated. Over the pristine Southern Ocean, it is found to improve the seasonal cycle of organic aerosol mass and cloud droplet number concentrations relative to GC3.1 although underestimations in cloud droplet number concentrations remain. This paper provides a useful characterisation of the aerosol climatology in both models and will facilitate understanding in the numerous aerosol' climate interaction studies that will be conducted as part of CMIP6 and beyond.
Abstract.
Kirdyanov AV, Krusic PJ, Shishov VV, Vaganov EA, Fertikov AI, Myglan VS, Barinov VV, Browse J, Esper J, Ilyin VA, et al (2020). Ecological and conceptual consequences of Arctic pollution.
Ecology Letters,
23(12), 1827-1837.
Abstract:
Ecological and conceptual consequences of Arctic pollution
AbstractAlthough the effect of pollution on forest health and decline received much attention in the 1980s, it has not been considered to explain the ‘Divergence Problem’ in dendroclimatology; a decoupling of tree growth from rising air temperatures since the 1970s. Here we use physical and biogeochemical measurements of hundreds of living and dead conifers to reconstruct the impact of heavy industrialisation around Norilsk in northern Siberia. Moreover, we develop a forward model with surface irradiance forcing to quantify long‐distance effects of anthropogenic emissions on the functioning and productivity of Siberia’s taiga. Downwind from the world’s most polluted Arctic region, tree mortality rates of up to 100% have destroyed 24,000 km2 boreal forest since the 1960s, coincident with dramatic increases in atmospheric sulphur, copper, and nickel concentrations. In addition to regional ecosystem devastation, we demonstrate how ‘Arctic Dimming’ can explain the circumpolar ‘Divergence Problem’, and discuss implications on the terrestrial carbon cycle.
Abstract.
Sanchez-Marroquin A, Arnalds O, Baustian-Dorsi KJ, Browse J, Dagsson-Waldhauserova P, Harrison AD, Maters EC, Pringle KJ, Vergara-Temprado J, Burke IT, et al (2020). Iceland is an episodic source of atmospheric ice-nucleating particles relevant for mixed-phase clouds.
Sci Adv,
6(26).
Abstract:
Iceland is an episodic source of atmospheric ice-nucleating particles relevant for mixed-phase clouds.
Ice-nucleating particles (INPs) have the potential to remove much of the liquid water in climatically important mid- to high-latitude shallow supercooled clouds, markedly reducing their albedo. The INP sources at these latitudes are very poorly defined, but it is known that there are substantial dust sources across the high latitudes, such as Iceland. Here, we show that Icelandic dust emissions are sporadically an important source of INPs at mid to high latitudes by combining ice-nucleating active site density measurements of aircraft-collected Icelandic dust samples with a global aerosol model. Because Iceland is only one of many high-latitude dust sources, we anticipate that the combined effect of all these sources may strongly contribute to the INP population in the mid- and high-latitude northern hemisphere. This is important because these emissions are directly relevant for the cloud-phase climate feedback and because high-latitude dust emissions are expected to increase in a warmer climate.
Abstract.
Author URL.
Johnson JS, Regayre LA, Yoshioka M, Pringle KJ, Turnock ST, Browse J, Sexton DMH, Rostron JW, Schutgens NAJ, Partridge DG, et al (2020). Robust observational constraint of uncertain aerosol processes and emissions in a climate model and the effect on aerosol radiative forcing.
ATMOSPHERIC CHEMISTRY AND PHYSICS,
20(15), 9491-9524.
Author URL.
2019
Yoshioka M, Regayre LA, Pringle KJ, Johnson JS, Mann GW, Partridge DG, Sexton DMH, Lister GMS, Schutgens N, Stier P, et al (2019). Ensembles of Global Climate Model Variants Designed for the Quantification and Constraint of Uncertainty in Aerosols and Their Radiative Forcing.
Journal of Advances in Modeling Earth Systems,
11(11), 3728-3754.
Abstract:
Ensembles of Global Climate Model Variants Designed for the Quantification and Constraint of Uncertainty in Aerosols and Their Radiative Forcing
Tropospheric aerosol radiative forcing has persisted for many years as one of the major causes of uncertainty in global climate model simulations. To sample the range of plausible aerosol and atmospheric states and perform robust statistical analyses of the radiative forcing, it is important to account for the combined effects of many sources of model uncertainty, which is rarely done due to the high computational cost. This paper describes the designs of two ensembles of the Met Office Hadley Centre Global Environment Model-U.K. Chemistry and Aerosol global climate model and provides the first analyses of the uncertainties in aerosol radiative forcing and their causes. The first ensemble was designed to comprehensively sample uncertainty in the aerosol state, while the other samples additional uncertainties in the physical model related to clouds, humidity, and radiation, thereby allowing an analysis of uncertainty in the aerosol effective radiative forcing. Each ensemble consists of around 200 simulations of the preindustrial and present-day atmospheres. The uncertainty in aerosol radiative forcing in our ensembles is comparable to the range of estimates from multimodel intercomparison projects. The mean aerosol effective radiative forcing is −1.45 W/m2 (credible interval of −2.07 to −0.81 W/m2), which encompasses but is more negative than the −1.17 W/m2 in the 2013 Atmospheric Chemistry and Climate Model Intercomparison Project and −0.90 W/m2 in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The ensembles can be used to reduce aerosol radiative forcing uncertainty by challenging them with multiple measurements as well as to isolate potential causes of multimodel differences.
Abstract.
Thomas JL, Stutz J, Frey MM, Bartels-Rausch T, Altieri K, Baladima F, Browse J, Dall’Osto M, Marelle L, Mouginot J, et al (2019). Fostering multidisciplinary research on interactions between chemistry, biology, and physics within the coupled cryosphere-atmosphere system. Elementa: Science of the Anthropocene, 7(1).
Johnson JS, Regayre LA, Yoshioka M, Pringle KJ, Turnock ST, Browse J, Sexton DMH, Rostron JW, Schutgens NAJ, Partridge DG, et al (2019). Robust observational constraint of uncertain aerosol processes and emissions in a climate model and the effect on aerosol radiative forcing. , 2019, 1-51.
Walters D, Baran AJ, Boutle I, Brooks M, Earnshaw P, Edwards J, Furtado K, Hi P, Lock A, Manners J, et al (2019). The Met Office Unified Model Global Atmosphere 7.0/7.1 and JULES Global Land 7.0 configurations.
GEOSCIENTIFIC MODEL DEVELOPMENT,
12(5), 1909-1963.
Author URL.
2018
Vergara-Temprado J, Holden MA, Orton TR, O'Sullivan D, Umo NS, Browse J, Reddington C, Baeza-Romero MT, Jones JM, Lea-Langton A, et al (2018). Is Black Carbon an Unimportant Ice-Nucleating Particle in Mixed-Phase Clouds?.
Journal of Geophysical Research: Atmospheres,
123(8), 4273-4283.
Abstract:
Is Black Carbon an Unimportant Ice-Nucleating Particle in Mixed-Phase Clouds?
It has been hypothesized that black carbon (BC) influences mixed-phase clouds by acting as an ice-nucleating particle (INP). However, the literature data for ice nucleation by BC immersed in supercooled water are extremely varied, with some studies reporting that BC is very effective at nucleating ice, whereas others report no ice-nucleating ability. Here we present new experimental results for immersion mode ice nucleation by BC from two contrasting fuels (n-decane and eugenol). We observe no significant heterogeneous nucleation by either sample. Using a global aerosol model, we quantify the maximum relative importance of BC for ice nucleation when compared with K-feldspar and marine organic aerosol acting as INP. Based on the upper limit from our laboratory data, we show that BC contributes at least several orders of magnitude less INP than feldspar and marine organic aerosol. Representations of its atmospheric ice-nucleating ability based on older laboratory data produce unrealistic results when compared against ambient observations of INP. Since BC is a complex material, it cannot be unambiguously ruled out as an important INP species in all locations at all times. Therefore, we use our model to estimate a range of values for the density of active sites that BC particles must have to be relevant for ice nucleation in the atmosphere. The estimated values will guide future work on BC, defining the required sensitivity of future experimental studies.
Abstract.
Herbert RJ, Krom MD, Carslaw KS, Stockdale A, Mortimer RJG, Benning LG, Pringle K, Browse J (2018). The Effect of Atmospheric Acid Processing on the Global Deposition of Bioavailable Phosphorus from Dust.
Global Biogeochemical Cycles,
32(9), 1367-1385.
Abstract:
The Effect of Atmospheric Acid Processing on the Global Deposition of Bioavailable Phosphorus from Dust
The role of dust as a source of bioavailable phosphorus (Bio-P) is quantified using a new parameterization for apatite dissolution in combination with global soil data maps and a global aerosol transport model. Mineral dust provides 31.2 Gg-P/year of Bio-P to the oceans, with 14.3 Gg-P/year from labile P present in the dust, and an additional 16.9 Gg-P/year from acid dissolution of apatite in the atmosphere, representing an increase of 120%. The North Atlantic, northwest Pacific, and Mediterranean Sea are identified as important sites of Bio-P deposition from mineral dust. The acid dissolution process increases the fraction of total-P that is bioavailable from ~10% globally from the labile pool to 18% in the Atlantic Ocean, 42% in the Pacific Ocean, and 20% in the Indian Ocean, with an ocean global mean value of 22%. Strong seasonal variations, especially in the North Pacific, northwest Atlantic, and Indian Ocean, are driven by large-scale meteorology and pollution sources from industrial and biomass-burning regions. Globally constant values of total-P content and bioavailable fraction used previously do not capture the simulated variability. We find particular sensitivity to the representation of particle-to-particle variability of apatite, which supplies Bio-P through acid-dissolution, and calcium carbonate, which helps to buffer the dissolution process. A modest 10% external mixing results in an increase of Bio-P deposition by 18%. The total Bio-P calculated here (31.2 Gg-P/year) represents a minimum compared to previous estimates due to the relatively low total-P in the global soil map used.
Abstract.
2017
Vergara-Temprado J, Murray BJ, Wilson TW, O'Sullivan D, Browse J, Pringle KJ, Ardon-Dryer K, Bertram AK, Burrows SM, Ceburnis D, et al (2017). Contribution of feldspar and marine organic aerosols to global ice nucleating particle concentrations.
Atmospheric Chemistry and Physics,
17(5), 3637-3658.
Abstract:
Contribution of feldspar and marine organic aerosols to global ice nucleating particle concentrations
Ice-nucleating particles (INPs) are known to affect the amount of ice in mixed-phase clouds, thereby influencing many of their properties. The atmospheric INP concentration changes by orders of magnitude from terrestrial to marine environments, which typically contain much lower concentrations. Many modelling studies use parameterizations for heterogeneous ice nucleation and cloud ice processes that do not account for this difference because they were developed based on INP measurements made predominantly in terrestrial environments without considering the aerosol composition. Errors in the assumed INP concentration will influence the simulated amount of ice in mixed-phase clouds, leading to errors in top-of-atmosphere radiative flux and ultimately the climate sensitivity of the model. Here we develop a global model of INP concentrations relevant for mixed-phase clouds based on laboratory and field measurements of ice nucleation by K-feldspar (an ice-active component of desert dust) and marine organic aerosols (from sea spray). The simulated global distribution of INP concentrations based on these two species agrees much better with currently available ambient measurements than when INP concentrations are assumed to depend only on temperature or particle size. Underestimation of INP concentrations in some terrestrial locations may be due to the neglect of INPs from other terrestrial sources. Our model indicates that, on a monthly average basis, desert dusts dominate the contribution to the INP population over much of the world, but marine organics become increasingly important over remote oceans and they dominate over the Southern Ocean. However, day-to-day variability is important. Because desert dust aerosol tends to be sporadic, marine organic aerosols dominate the INP population on many days per month over much of the mid- and high-latitude Northern Hemisphere. This study advances our understanding of which aerosol species need to be included in order to adequately describe the global and regional distribution of INPs in models, which will guide ice nucleation researchers on where to focus future laboratory and field work.
Abstract.
Walters D, Baran A, Boutle I, Brooks M, Earnshaw P, Edwards J, Furtado K, Hill P, Lock A, Manners J, et al (2017). The Met Office Unified Model Global Atmosphere 7.0/7.1 and JULES Global Land 7.0 configurations. , 1-78.
Reddington CL, Carslaw KS, Stier P, Schutgens N, Coe H, Liu D, Allan J, Browse J, Pringle KJ, Lee LA, et al (2017). The global aerosol synthesis and science project (GASSP): Measurements and modeling to reduce uncertainty. Bulletin of the American Meteorological Society, 98(9), 1857-1877.
2016
Arnold SR, Law KS, Brock CA, Thomas JL, Starkweather SM, von Salzen K, Stohl A, Sharma S, Lund MT, Flanner MG, et al (2016). Arctic air pollution: Challenges and opportunities for the next decade. Elementa: Science of the Anthropocene, 4, 000104-000104.
Temprado JV, Wilson TW, O'Sullivan D, Browse J, Pringle KJ, Ardon-Dryer K, Bertram AK, Burrows SM, Ceburnis D, DeMott PJ, et al (2016). Contribution of feldspar and marine organic aerosols to global ice nucleating particle concentrations. , 0, 1-37.
2015
Wilson TW, Ladino LA, Alpert PA, Breckels MN, Brooks IM, Browse J, Burrows SM, Carslaw KS, Huffman JA, Judd C, et al (2015). A marine biogenic source of atmospheric ice-nucleating particles.
Nature,
525(7568), 234-238.
Abstract:
A marine biogenic source of atmospheric ice-nucleating particles
The amount of ice present in clouds can affect cloud lifetime, precipitation and radiative properties. The formation of ice in clouds is facilitated by the presence of airborne ice-nucleating particles. Sea spray is one of the major global sources of atmospheric particles, but it is unclear to what extent these particles are capable of nucleating ice. Sea-spray aerosol contains large amounts of organic material that is ejected into the atmosphere during bubble bursting at the organically enriched sea-air interface or sea surface microlayer. Here we show that organic material in the sea surface microlayer nucleates ice under conditions relevant for mixed-phase cloud and high-altitude ice cloud formation. The ice-nucleating material is probably biogenic and less than approximately 0.2 micrometres in size. We find that exudates separated from cells of the marine diatom Thalassiosira pseudonana nucleate ice, and propose that organic material associated with phytoplankton cell exudates is a likely candidate for the observed ice-nucleating ability of the microlayer samples. Global model simulations of marine organic aerosol, in combination with our measurements, suggest that marine organic material may be an important source of ice-nucleating particles in remote marine environments such as the Southern Ocean, North Pacific Ocean and North Atlantic Ocean.
Abstract.
Regayre LA, Pringle KJ, Lee LA, Rap A, Browse J, Mann GW, Reddington CL, Carslaw KS, Booth BBB, Woodhouse MT, et al (2015). The climatic importance of uncertainties in regional aerosol-cloud radiative forcings over recent decades.
Journal of Climate,
28(17), 6589-6607.
Abstract:
The climatic importance of uncertainties in regional aerosol-cloud radiative forcings over recent decades
Regional patterns of aerosol radiative forcing are important for understanding climate change on decadal time scales. Uncertainty in aerosol forcing is likely to vary regionally and seasonally because of the short aerosol lifetime and heterogeneous emissions. Here the sensitivity of regional aerosol cloud albedo effect (CAE) forcing to 31 aerosol process parameters and emission fluxes is quantified between 1978 and 2008. The effects of parametric uncertainties on calculations of the balance of incoming and outgoing radiation are found to be spatially and temporally dependent. Regional uncertainty contributions of opposite sign cancel in global-mean forcing calculations, masking the regional importance of some parameters. Parameters that contribute little to uncertainty in Earth's global energy balance during recent decades make significant contributions to regional forcing variance. Aerosol forcing sensitivities are quantified within 11 climatically important regions, where surface temperatures are thought to influence large-scale climate effects. Substantial simulated uncertainty in CAE forcing in the eastern Pacific leaves open the possibility that apparent shifts in the mean ENSO state may result from a forced aerosol signal on multidecadal time scales. A likely negative aerosol CAE forcing in the tropical North Atlantic calls into question the relationship between Northern Hemisphere aerosol emission reductions and CAE forcing of sea surface temperatures in the main Atlantic hurricane development region on decadal time scales. Simulated CAE forcing uncertainty is large in the North Pacific, suggesting that the role of the CAE in altering Pacific tropical storm frequency and intensity is also highly uncertain.
Abstract.
2014
O'Sullivan D, Murray BJ, Malkin TL, Whale TF, Umo NS, Atkinson JD, Price HC, Baustian KJ, Browse J, Webb ME, et al (2014). Ice nucleation by fertile soil dusts: Relative importance of mineral and biogenic components.
Atmospheric Chemistry and Physics,
14(4), 1853-1867.
Abstract:
Ice nucleation by fertile soil dusts: Relative importance of mineral and biogenic components
Agricultural dust emissions have been estimated to contribute around 20% to the global dust burden. In contrast to dusts from arid source regions, the ice-nucleating abilities of which have been relatively well studied, soil dusts from fertile sources often contain a substantial fraction of organic matter. Using an experimental methodology which is sensitive to a wide range of ice nucleation efficiencies, we have characterised the immersion mode ice-nucleating activities of dusts (d
Abstract.
Browse J, Carslaw KS, Mann GW, Birch CE, Arnold SR, Leck C (2014). The complex response of Arctic aerosol to sea-ice retreat.
Atmospheric Chemistry and Physics,
14(14), 7543-7557.
Abstract:
The complex response of Arctic aerosol to sea-ice retreat
Loss of summertime Arctic sea ice will lead to a large increase in the emission of aerosols and precursor gases from the ocean surface. It has been suggested that these enhanced emissions will exert substantial aerosol radiative forcings, dominated by the indirect effect of aerosol on clouds. Here, we investigate the potential for these indirect forcings using a global aerosol microphysics model evaluated against aerosol observations from the Arctic Summer Cloud Ocean Study (ASCOS) campaign to examine the response of Arctic cloud condensation nuclei (CCN) to sea-ice retreat. In response to a complete loss of summer ice, we find that north of 70° N emission fluxes of sea salt, marine primary organic aerosol (OA) and dimethyl sulfide increase by a factor of ∼ 10, ∼ 4 and ∼ 15 respectively. However, the CCN response is weak, with negative changes over the central Arctic Ocean. The weak response is due to the efficient scavenging of aerosol by extensive drizzling stratocumulus clouds. In the scavenging-dominated Arctic environment, the production of condensable vapour from oxidation of dimethyl sulfide grows particles to sizes where they can be scavenged. This loss is not sufficiently compensated by new particle formation, due to the suppression of nucleation by the large condensation sink resulting from sea-salt and primary OA emissions. Thus, our results suggest that increased aerosol emissions will not cause a climate feedback through changes in cloud microphysical and radiative properties. © Author(s) 2014.
Abstract.
Regayre LA, Pringle KJ, Booth BBB, Lee LA, Mann GW, Browse J, Woodhouse MT, Rap A, Reddington CL, Carslaw KS, et al (2014). Uncertainty in the magnitude of aerosol-cloud radiative forcing over recent decades.
Geophysical Research Letters,
41(24), 9040-9049.
Abstract:
Uncertainty in the magnitude of aerosol-cloud radiative forcing over recent decades
Aerosols and their effect on the radiative properties of clouds are one of the largest sources of uncertainty in calculations of the Earth's energy budget. Here the sensitivity of aerosol-cloud albedo effect forcing to 31 aerosol parameters is quantified. Sensitivities are compared over three periods; 1850-2008, 1978-2008, and 1998-2008. Despite declining global anthropogenic SO2 emissions during 1978-2008, a cancelation of regional positive and negative forcings leads to a near-zero global mean cloud albedo effect forcing. In contrast to existing negative estimates, our results suggest that the aerosol-cloud albedo effect was likely positive (0.006 to 0.028Wm-2) in the recent decade, making it harder to explain the temperature hiatus as a forced response. Proportional contributions to forcing variance from aerosol processes and natural and anthropogenic emissions are found to be period dependent. To better constrain forcing estimates, the processes that dominate uncertainty on the timescale of interest must be better understood. Key Points Forcing sensitivity to aerosol parameters is strongly period dependentUnderstanding near-future climate is limited if a single period is consideredIn recent decades, parametric uncertainty is smaller than model diversity
Abstract.
2013
O'Sullivan D, Murray BJ, Malkin TL, Whale T, Umo NS, Atkinson JD, Price HC, Baustian KJ, Browse J, Webb ME, et al (2013). Ice nucleation by soil dusts: relative importance of mineral dust and biogenic components. , 13(8), 20275-20317.
Browse J, Carslaw KS, Schmidt A, Corbett JJ (2013). Impact of future Arctic shipping on high-latitude black carbon deposition.
Geophysical Research Letters,
40(16), 4459-4463.
Abstract:
Impact of future Arctic shipping on high-latitude black carbon deposition
The retreat of Arctic sea ice has led to renewed calls to exploit Arctic shipping routes. The diversion of ship traffic through the Arctic will shorten shipping routes and possibly reduce global shipping emissions. However, deposition of black carbon (BC) aerosol emitted by additional Arctic ships could cause a reduction in the albedo of snow and ice, accelerating snowmelt and sea ice loss. Here we use recently compiled Arctic shipping emission inventories for 2004 and 2050 together with a global aerosol model to quantify the contribution of future Arctic shipping to high-latitude BC deposition. Our results show that Arctic shipping in 2050 will contribute less than 1% to the total BC deposition north of 60°N due to the much greater relative contribution of BC transported from non-shipping sources at lower latitudes. We suggest that regulation of the Arctic shipping industry will be an insufficient control on high-latitude BC deposition. Key Points Contribution of Arctic shipping to high-latitude BC deposition less than 1% Extra-Arctic sources contribute much greater Arctic BC mass than local shipping Regulation of Arctic shipping unlikely to control high-latitude BC deposition. © 2013. American Geophysical Union. All Rights Reserved.
Abstract.
Browse J, Carslaw KS, Mann GW, Birch CE, Arnold SR, Leck C (2013). The complex response of Arctic cloud condensation nuclei to sea-ice retreat. , 13(6), 17087-17121.
2012
Browse J, Carslaw KS, Arnold SR, Pringle K, Boucher O (2012). The scavenging processes controlling the seasonal cycle in Arctic sulphate and black carbon aerosol. , 12(1), 3409-3465.
Browse J, Carslaw KS, Arnold SR, Pringle K, Boucher O (2012). The scavenging processes controlling the seasonal cycle in Arctic sulphate and black carbon aerosol.
Atmospheric Chemistry and Physics,
12(15), 6775-6798.
Abstract:
The scavenging processes controlling the seasonal cycle in Arctic sulphate and black carbon aerosol
The seasonal cycle in Arctic aerosol is typified by high concentrations of large aged anthropogenic particles transported from lower latitudes in the late Arctic winter and early spring followed by a sharp transition to low concentrations of locally sourced smaller particles in the summer. However, multi-model assessments show that many models fail to simulate a realistic cycle. Here, we use a global aerosol microphysics model (GLOMAP) and surface-level aerosol observations to understand how wet scavenging processes control the seasonal variation in Arctic black carbon (BC) and sulphate aerosol. We show that the transition from high wintertime concentrations to low concentrations in the summer is controlled by the transition from ice-phase cloud scavenging to the much more efficient warm cloud scavenging in the late spring troposphere. This seasonal cycle is amplified further by the appearance of warm drizzling cloud in the late spring and summer boundary layer. Implementing these processes in GLOMAP greatly improves the agreement between the model and observations at the three Arctic ground-stations Alert, Barrow and Zeppelin Mountain on Svalbard. The SO4 model-observation correlation coefficient (R) increases from:-0.33 to 0.71 at Alert (82.5 N), from-0.16 to 0.70 at Point Barrow (71.0 N) and from-0.42 to 0.40 at Zeppelin Mountain (78 N). The BC model-observation correlation coefficient increases from-0.68 to 0.72 at Alert and from-0.42 to 0.44 at Barrow. Observations at three marginal Arctic sites (Janiskoski, Oulanka and Karasjok) indicate a far weaker aerosol seasonal cycle, which we show is consistent with the much smaller seasonal change in the frequency of ice clouds compared to higher latitude sites. Our results suggest that the seasonal cycle in Arctic aerosol is driven by temperature-dependent scavenging processes that may be susceptible to modification in a future climate. © 2012 Author(s).
Abstract.
