Rising natural aerosols drive marine radiative forcing as pollution declines

Rising natural aerosols drive marine radiative forcing as pollution declines | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Physical Sciences - Article Rising natural aerosols drive marine radiative forcing as pollution declines Vaios Moschos, Emmanuel Chevassus, Kirsten Fossum, Lu Lei, Jakob Pernov, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8776460/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Atmospheric aerosol particles are the leading uncertainty in climate forcing because they both reflect and absorb sunlight. Over the oceans, this influence is poorly constrained because long-term, composition-resolved observations are rare and natural sources vary widely. Using 2008–2019 aerosol records from interhemispheric observatories at Mace Head (Ireland) and Kennaook/Cape Grim (Tasmania), we show that increasing natural aerosol concentrations are driving increasingly negative marine aerosol forcing. After removing seasonality and quantifying trends across the concentration distribution, we find that at Mace Head historical declines in ammonium-sulfate and combustion-derived organics have largely levelled off, and the net anthropogenic forcing trend is now indistinguishable from zero because reduced scattering is offset by weaker black/brown carbon absorption. By contrast, increases in sea-salt, biogenic sulfate and marine organics drive a robust cooling trend (median −0.03 W m −2 decade −1 ; −0.05 W m −2 decade −1 at background levels). At Kennaook/Cape Grim, decreasing black carbon alongside increasing biogenic sulfate indicates that this shift is not confined to the North Atlantic. Meanwhile, extreme aerosol episodes linked to wildfire smoke, marine blooms and long-range transport also increase. These results show that evolving natural aerosol sources must be represented in climate models to correctly attribute and project near-term marine forcing. Earth and environmental sciences/Climate sciences/Atmospheric science/Atmospheric chemistry Earth and environmental sciences/Environmental sciences/Environmental chemistry/Marine chemistry Full Text Additional Declarations There is NO Competing Interest. Supplementary Files MoschosetalSI.pdf Moschos_etal_SI Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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