The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere
Abstract Solar geoengineering by deliberate injection of sulfate aerosols in the stratosphere is one of the proposed options to counter anthropogenic climate warming. In this study, we focus on the effect of a specific microphysical property of sulfate aerosols in the stratosphere: hygroscopic growt...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Wiley
2020-02-01
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| Series: | Earth's Future |
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| Online Access: | https://doi.org/10.1029/2019EF001326 |
| _version_ | 1818471967341150208 |
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| author | K.S. Krishnamohan Govindasamy Bala Long Cao Lei Duan Ken Caldeira |
| author_facet | K.S. Krishnamohan Govindasamy Bala Long Cao Lei Duan Ken Caldeira |
| author_sort | K.S. Krishnamohan |
| collection | DOAJ |
| description | Abstract Solar geoengineering by deliberate injection of sulfate aerosols in the stratosphere is one of the proposed options to counter anthropogenic climate warming. In this study, we focus on the effect of a specific microphysical property of sulfate aerosols in the stratosphere: hygroscopic growth—the tendency of particles to grow by accumulating water. We show that stratospheric sulfate aerosols, for a given mass of sulfates, cause more cooling when prescribed at the lower levels of the stratosphere because of hygroscopic growth. The larger relative humidity in the lower stratosphere causes an increase in the aerosol size through hygroscopic growth that leads to a larger scattering efficiency. In our study, hygroscopic growth provides an additional cooling of 23% (0.7 K) when 20 Mt‐SO4 of sulfate aerosols, an amount that approximately offsets the warming due to a doubling of CO2, are prescribed at 100 hPa. The hygroscopic effect becomes weaker at higher levels as relative humidity decreases with height. Hygroscopic growth also leads to secondary effects such as an increase in near‐infrared shortwave absorption by the aerosols that causes a decrease in high clouds and an increase in stratospheric water vapor. The altitude dependence of the effects of hygroscopic growth is opposite to that of sedimentation effects or the fast adjustment effects due to aerosol‐induced warming identified in a recent study. |
| first_indexed | 2024-04-14T03:59:01Z |
| format | Article |
| id | doaj.art-4b26e6c7a7204f18876763bfdcd0e6d8 |
| institution | Directory Open Access Journal |
| issn | 2328-4277 |
| language | English |
| last_indexed | 2024-04-14T03:59:01Z |
| publishDate | 2020-02-01 |
| publisher | Wiley |
| record_format | Article |
| series | Earth's Future |
| spelling | doaj.art-4b26e6c7a7204f18876763bfdcd0e6d82022-12-22T02:13:38ZengWileyEarth's Future2328-42772020-02-0182n/an/a10.1029/2019EF001326The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the StratosphereK.S. Krishnamohan0Govindasamy Bala1Long Cao2Lei Duan3Ken Caldeira4Centre for Atmospheric and Oceanic Sciences Indian Institute of Science Bangalore IndiaCentre for Atmospheric and Oceanic Sciences Indian Institute of Science Bangalore IndiaDepartment of Atmospheric Sciences, School of Earth Sciences Zhejiang University Hangzhou ChinaDepartment of Atmospheric Sciences, School of Earth Sciences Zhejiang University Hangzhou ChinaDepartment of Global Ecology Carnegie Institution for Science Stanford CA USAAbstract Solar geoengineering by deliberate injection of sulfate aerosols in the stratosphere is one of the proposed options to counter anthropogenic climate warming. In this study, we focus on the effect of a specific microphysical property of sulfate aerosols in the stratosphere: hygroscopic growth—the tendency of particles to grow by accumulating water. We show that stratospheric sulfate aerosols, for a given mass of sulfates, cause more cooling when prescribed at the lower levels of the stratosphere because of hygroscopic growth. The larger relative humidity in the lower stratosphere causes an increase in the aerosol size through hygroscopic growth that leads to a larger scattering efficiency. In our study, hygroscopic growth provides an additional cooling of 23% (0.7 K) when 20 Mt‐SO4 of sulfate aerosols, an amount that approximately offsets the warming due to a doubling of CO2, are prescribed at 100 hPa. The hygroscopic effect becomes weaker at higher levels as relative humidity decreases with height. Hygroscopic growth also leads to secondary effects such as an increase in near‐infrared shortwave absorption by the aerosols that causes a decrease in high clouds and an increase in stratospheric water vapor. The altitude dependence of the effects of hygroscopic growth is opposite to that of sedimentation effects or the fast adjustment effects due to aerosol‐induced warming identified in a recent study.https://doi.org/10.1029/2019EF001326stratospheric sulfate geoengineeringhygroscopic growthscattering efficiencysulfate aerosolsradiative forcing |
| spellingShingle | K.S. Krishnamohan Govindasamy Bala Long Cao Lei Duan Ken Caldeira The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere Earth's Future stratospheric sulfate geoengineering hygroscopic growth scattering efficiency sulfate aerosols radiative forcing |
| title | The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere |
| title_full | The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere |
| title_fullStr | The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere |
| title_full_unstemmed | The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere |
| title_short | The Climatic Effects of Hygroscopic Growth of Sulfate Aerosols in the Stratosphere |
| title_sort | climatic effects of hygroscopic growth of sulfate aerosols in the stratosphere |
| topic | stratospheric sulfate geoengineering hygroscopic growth scattering efficiency sulfate aerosols radiative forcing |
| url | https://doi.org/10.1029/2019EF001326 |
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