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Feingold G, Ghate VP, Russell LM, Blossey P, Cantrell W, Christensen MW, Diamond MS, Gettelman A, Glassmeier F, Gryspeerdt E, Haywood J, Hoffmann F, Kaul CM, Lebsock M, McComiskey AC, McCoy DT, Ming Y, Mülmenstädt J, Possner A, Prabhakaran P, Quinn PK, Schmidt KS, Shaw RA, Singer CE, Sorooshian A, Toll V, Wan JS, Wood R, Yang F, Zhang J, Zheng X. Physical science research needed to evaluate the viability and risks of marine cloud brightening. Sci Adv 2024; 10:eadi8594. [PMID: 38507486 PMCID: PMC10954212 DOI: 10.1126/sciadv.adi8594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 02/14/2024] [Indexed: 03/22/2024]
Abstract
Marine cloud brightening (MCB) is the deliberate injection of aerosol particles into shallow marine clouds to increase their reflection of solar radiation and reduce the amount of energy absorbed by the climate system. From the physical science perspective, the consensus of a broad international group of scientists is that the viability of MCB will ultimately depend on whether observations and models can robustly assess the scale-up of local-to-global brightening in today's climate and identify strategies that will ensure an equitable geographical distribution of the benefits and risks associated with projected regional changes in temperature and precipitation. To address the physical science knowledge gaps required to assess the societal implications of MCB, we propose a substantial and targeted program of research-field and laboratory experiments, monitoring, and numerical modeling across a range of scales.
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Affiliation(s)
| | | | - Lynn M. Russell
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | | | - Will Cantrell
- Michigan Technological University, Houghton, MI, USA
| | | | | | | | | | | | | | | | | | - Matthew Lebsock
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
| | | | | | - Yi Ming
- Boston College, Chestnut Hill, MA, USA
| | | | | | - Prasanth Prabhakaran
- NOAA Chemical Sciences Laboratory, Boulder, CO, USA
- CIRES, University of Colorado, Boulder, CO, USA
| | | | | | | | | | | | | | - Jessica S. Wan
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA, USA
| | | | - Fan Yang
- National Center for Atmospheric Research, Boulder, CO, USA
| | - Jianhao Zhang
- NOAA Chemical Sciences Laboratory, Boulder, CO, USA
- CIRES, University of Colorado, Boulder, CO, USA
| | - Xue Zheng
- Lawrence Livermore National Laboratory, Livermore, CA, USA
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Christensen MW, Gettelman A, Cermak J, Dagan G, Diamond M, Douglas A, Feingold G, Glassmeier F, Goren T, Grosvenor DP, Gryspeerdt E, Kahn R, Li Z, Ma PL, Malavelle F, McCoy IL, McCoy DT, McFarquhar G, Mülmenstädt J, Pal S, Possner A, Povey A, Quaas J, Rosenfeld D, Schmidt A, Schrödner R, Sorooshian A, Stier P, Toll V, Watson-Parris D, Wood R, Yang M, Yuan T. Opportunistic experiments to constrain aerosol effective radiative forcing. Atmos Chem Phys 2022; 22:641-674. [PMID: 35136405 PMCID: PMC8819675 DOI: 10.5194/acp-22-641-2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Aerosol-cloud interactions (ACIs) are considered to be the most uncertain driver of present-day radiative forcing due to human activities. The nonlinearity of cloud-state changes to aerosol perturbations make it challenging to attribute causality in observed relationships of aerosol radiative forcing. Using correlations to infer causality can be challenging when meteorological variability also drives both aerosol and cloud changes independently. Natural and anthropogenic aerosol perturbations from well-defined sources provide "opportunistic experiments" (also known as natural experiments) to investigate ACI in cases where causality may be more confidently inferred. These perturbations cover a wide range of locations and spatiotemporal scales, including point sources such as volcanic eruptions or industrial sources, plumes from biomass burning or forest fires, and tracks from individual ships or shipping corridors. We review the different experimental conditions and conduct a synthesis of the available satellite datasets and field campaigns to place these opportunistic experiments on a common footing, facilitating new insights and a clearer understanding of key uncertainties in aerosol radiative forcing. Cloud albedo perturbations are strongly sensitive to background meteorological conditions. Strong liquid water path increases due to aerosol perturbations are largely ruled out by averaging across experiments. Opportunistic experiments have significantly improved process-level understanding of ACI, but it remains unclear how reliably the relationships found can be scaled to the global level, thus demonstrating a need for deeper investigation in order to improve assessments of aerosol radiative forcing and climate change.
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Affiliation(s)
- Matthew W. Christensen
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
- Atmospheric Science & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99354, Washington, USA
| | | | - Jan Cermak
- Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research, Karlsruhe, Germany
- Karlsruhe Institute of Technology (KIT), Institute of Photogrammetry and Remote Sensing, Karlsruhe, Germany
| | - Guy Dagan
- Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Michael Diamond
- Department of Atmospheric Sciences, University of Washington, Seattle, USA
- NOAA Chemical Sciences Laboratory (CSL), Boulder, Colorado, USA
- Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, Colorado, USA
| | - Alyson Douglas
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Graham Feingold
- NOAA Chemical Sciences Laboratory (CSL), Boulder, Colorado, USA
| | - Franziska Glassmeier
- Department Geoscience and Remote Sensing, Delft University of Technology, P.O. Box 5048, 2600GA Delft, the Netherlands
| | - Tom Goren
- Institute for Meteorology, Universität Leipzig, Leipzig, Germany
| | - Daniel P. Grosvenor
- National Centre for Atmospheric Sciences, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
| | - Edward Gryspeerdt
- Space and Atmospheric Physics Group, Imperial College London, London, UK
| | - Ralph Kahn
- Earth Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
| | - Zhanqing Li
- Department of Atmospheric and Oceanic Science, University of Maryland, College Park, USA
| | - Po-Lun Ma
- Atmospheric Science & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99354, Washington, USA
| | - Florent Malavelle
- Met Office, Atmospheric Dispersion and Air Quality, Fitzroy Rd, Exeter, EX1 3PB, UK
| | - Isabel L. McCoy
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA
- Cooperative Programs for the Advancement of Earth System Science (CPAESS), University Corporation for Atmospheric Research, Boulder, CO, USA
| | - Daniel T. McCoy
- Department of Atmospheric Sciences, University of Wyoming, Laramie, USA
| | - Greg McFarquhar
- Cooperative Institute for Severe and High Impact Weather Research and Operations (CIWRO) and School of Meteorology, University of Oklahoma, Norman, OK, USA
- School of Meteorology, University of Oklahoma, Norman, OK, USA
| | - Johannes Mülmenstädt
- Atmospheric Science & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99354, Washington, USA
| | - Sandip Pal
- Department of Geosciences, Texas Tech University, Lubbock, TX, USA
| | - Anna Possner
- Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Adam Povey
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
- National Centre for Earth Observation, University of Oxford, Oxford, OX1 3PU, UK
| | - Johannes Quaas
- Institute for Meteorology, Universität Leipzig, Leipzig, Germany
| | - Daniel Rosenfeld
- Institute of Earth Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Anja Schmidt
- Department of Geography, University of Cambridge, Cambridge, UK
- Department of Chemistry, University of Cambridge, Cambridge, UK
| | | | - Armin Sorooshian
- Department of Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA
- Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
| | - Philip Stier
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Velle Toll
- Institute of Physics, University of Tartu, Tartu, Estonia
| | - Duncan Watson-Parris
- Atmospheric, Oceanic and Planetary Physics, Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Robert Wood
- Department of Atmospheric Sciences, University of Washington, Seattle, USA
| | - Mingxi Yang
- Plymouth Marine Laboratory, Prospect Place, Plymouth, PL1 3DH, UK
| | - Tianle Yuan
- Joint Center for Earth Systems Technologies, University of Maryland, Baltimore County, Baltimore, MD, USA
- Earth Science Division, NASA Goddard Space Flight Center, Greenbelt, MD, USA
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McCoy IL, McCoy DT, Wood R, Regayre L, Watson-Parris D, Grosvenor DP, Mulcahy JP, Hu Y, Bender FAM, Field PR, Carslaw KS, Gordon H. The hemispheric contrast in cloud microphysical properties constrains aerosol forcing. Proc Natl Acad Sci U S A 2020; 117:18998-19006. [PMID: 32719114 PMCID: PMC7431023 DOI: 10.1073/pnas.1922502117] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The change in planetary albedo due to aerosol-cloud interactions during the industrial era is the leading source of uncertainty in inferring Earth's climate sensitivity to increased greenhouse gases from the historical record. The variable that controls aerosol-cloud interactions in warm clouds is droplet number concentration. Global climate models demonstrate that the present-day hemispheric contrast in cloud droplet number concentration between the pristine Southern Hemisphere and the polluted Northern Hemisphere oceans can be used as a proxy for anthropogenically driven change in cloud droplet number concentration. Remotely sensed estimates constrain this change in droplet number concentration to be between 8 cm-3 and 24 cm-3 By extension, the radiative forcing since 1850 from aerosol-cloud interactions is constrained to be -1.2 W⋅m-2 to -0.6 W⋅m-2 The robustness of this constraint depends upon the assumption that pristine Southern Ocean droplet number concentration is a suitable proxy for preindustrial concentrations. Droplet number concentrations calculated from satellite data over the Southern Ocean are high in austral summer. Near Antarctica, they reach values typical of Northern Hemisphere polluted outflows. These concentrations are found to agree with several in situ datasets. In contrast, climate models show systematic underpredictions of cloud droplet number concentration across the Southern Ocean. Near Antarctica, where precipitation sinks of aerosol are small, the underestimation by climate models is particularly large. This motivates the need for detailed process studies of aerosol production and aerosol-cloud interactions in pristine environments. The hemispheric difference in satellite estimated cloud droplet number concentration implies preindustrial aerosol concentrations were higher than estimated by most models.
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Affiliation(s)
- Isabel L McCoy
- Atmospheric Sciences Department, University of Washington, Seattle, WA 98105;
| | - Daniel T McCoy
- Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Robert Wood
- Atmospheric Sciences Department, University of Washington, Seattle, WA 98105
| | - Leighton Regayre
- Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom
| | | | - Daniel P Grosvenor
- Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom
- National Center for Atmospheric Science, University of Leeds, LS2 9JT Leeds, United Kingdom
| | | | - Yongxiang Hu
- Atmospheric Composition Branch, NASA Langley Research Center, Hampton, VA 23681
| | - Frida A-M Bender
- Department of Meteorology, Stockholm University, SE-106 91 Stockholm, Sweden
- Bolin Centre for Climate Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Paul R Field
- Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom
- Met Office, Exeter EX1 3PB, United Kingdom
| | - Kenneth S Carslaw
- Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom
| | - Hamish Gordon
- Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, LS2 9JT Leeds, United Kingdom
- College of Engineering, Carnegie-Mellon University, Pittsburgh, PA 15213
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McCoy DT, Burrows SM, Wood R, Grosvenor DP, Elliott SM, Ma PL, Rasch PJ, Hartmann DL. Natural aerosols explain seasonal and spatial patterns of Southern Ocean cloud albedo. Sci Adv 2015; 1:e1500157. [PMID: 26601216 PMCID: PMC4646780 DOI: 10.1126/sciadv.1500157] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 05/07/2015] [Indexed: 05/08/2023]
Abstract
Atmospheric aerosols, suspended solid and liquid particles, act as nucleation sites for cloud drop formation, affecting clouds and cloud properties-ultimately influencing the cloud dynamics, lifetime, water path, and areal extent that determine the reflectivity (albedo) of clouds. The concentration N d of droplets in clouds that influences planetary albedo is sensitive to the availability of aerosol particles on which the droplets form. Natural aerosol concentrations affect not only cloud properties themselves but also modulate the sensitivity of clouds to changes in anthropogenic aerosols. It is shown that modeled natural aerosols, principally marine biogenic primary and secondary aerosol sources, explain more than half of the spatiotemporal variability in satellite-observed N d. Enhanced N d is spatially correlated with regions of high chlorophyll a, and the spatiotemporal variability in N d is found to be driven primarily by high concentrations of sulfate aerosol at lower Southern Ocean latitudes (35(o) to 45(o)S) and by organic matter in sea spray aerosol at higher latitudes (45(o) to 55(o)S). Biogenic sources are estimated to increase the summertime mean reflected solar radiation in excess of 10 W m(-2) over parts of the Southern Ocean, which is comparable to the annual mean increases expected from anthropogenic aerosols over heavily polluted regions of the Northern Hemisphere.
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Affiliation(s)
- Daniel T. McCoy
- Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195–1640, USA
- Corresponding author. E-mail: (D.T.M.); (S.M.B.)
| | - Susannah M. Burrows
- Atmospheric Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
- Corresponding author. E-mail: (D.T.M.); (S.M.B.)
| | - Robert Wood
- Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195–1640, USA
| | | | - Scott M. Elliott
- Climate Ocean Sea Ice Modeling team, Computational Physics and Methods group, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Po-Lun Ma
- Atmospheric Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Phillip J. Rasch
- Atmospheric Sciences Division, Pacific Northwest National Laboratory, Richland, WA 99352, USA
| | - Dennis L. Hartmann
- Department of Atmospheric Sciences, University of Washington, Seattle, WA 98195–1640, USA
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