Amplified future drying of tropical land constrained by physical theory

Amplified future drying of tropical land constrained by physical theory | 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 Article Amplified future drying of tropical land constrained by physical theory Andrew Chingos, Graeme A. MacGilchrist, Michael Byrne This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8604145/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Near-surface relative humidity is a fundamental metric of land climate, modulating temperature, precipitation, evapotranspiration, wildfires, and heat stress in a warming world. The response of relative humidity over land to climate change is likely to be substantial but remains uncertain, with climate models projecting a wide range of future changes. Previous work highlighted the inability of models to accurately reproduce observed decreases in land relative humidity over the historical period, inviting scrutiny of the veracity of their future projections. Here, to constrain model projections of land relative humidity, we derive a simple physical theory -- grounded in an ocean‐influence perspective on boundary-layer moisture over land -- that links fractional changes in tropical land relative humidity to the land–ocean warming contrast. According to this theory, due to stronger warming over land relative to oceans in a changing climate, increases in the water-holding capacity of air over land outpace increases in the supply of moisture from oceanic regions, implying a decrease in land relative humidity. The ocean‐influence theory explains much of the spread across models in historical land relative humidity trends as well as the trend in reanalysis data. Combining the theory with observational estimates of the radiatively-forced land-ocean warming contrast, we obtain constrained estimates of future tropical land relative humidity change (–6.4 %/K assuming a climate-invariant warming contrast; -4.4 %/K when changes in warming contrast across climate states are accounted for). Both constrained estimates suggest substantially stronger tropical drying compared to the unconstrained multi-model median change (-1.5 %/K). This emergent constraint emphasises the systematic underestimation of future drying by models and reveals its physical basis, with important implications for projecting land-climate impacts and sharpening directions for future research to minimise this key model bias. Earth and environmental sciences/Climate sciences/Climate change/Projection and prediction Earth and environmental sciences/Climate sciences/Climate change/Climate and Earth system modelling Earth and environmental sciences/Climate sciences/Atmospheric science/Atmospheric dynamics Earth and environmental sciences/Climate sciences/Climate change/Climate-change impacts Full Text Additional Declarations There is NO Competing Interest. Supplementary Files Supplementaryinformation.pdf Supplementary Information for Amplified future drying of tropical land constrained by physical theory Cite Share Download PDF Status: Posted 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8604145","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":574912721,"identity":"bdb3d8b7-f08b-4875-8eaf-5f6e519aaf8f","order_by":0,"name":"Andrew Chingos","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA8UlEQVRIie2RsWrDMBCGzwicRaD1vKSvoBAIePKrWBg8mc4eglEpOC8R+hiebQTuouwOHqIs7eKhY7u0tcnQoURJtgz6puO4j7ufA3A47hPPxPmpwr9mbVUIN/o0fbXiB8fyFoVtng2Kl6KA2a7p81xFMFOGUH1eQd1yLiqFQB+TUGslJE05oZ3lrC6DWFQ1RnW2Cp7KPgbIgNCP88bDYYBabAsENozKdx+NhV3hHfWkkAQBpy2y9yROWyyHLXS6hLhVgcRhGcr2R5T4xputJf78Vb1/fa4LBixb7OU6jRhLjmZoLfH/4cOlRzocDofjIr+M4lBVNFNlsAAAAABJRU5ErkJggg==","orcid":"https://orcid.org/0000-0002-0113-8963","institution":"University of St Andrews","correspondingAuthor":true,"prefix":"","firstName":"Andrew","middleName":"","lastName":"Chingos","suffix":""},{"id":574912722,"identity":"af45f2f2-99b4-47b3-ab95-15c8385323c9","order_by":1,"name":"Graeme A. 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