{"paper_id":"4238a4b4-2cbf-4679-9a3d-ecc64bac2816","body_text":"Constraining climate model projections with observations amplifies future runoff 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 Article Constraining climate model projections with observations amplifies future runoff declines Hanjun Kim, Flavio Lehner, Katherine Dagon, David Lawrence, Sean Swenson, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5867679/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 27 Jan, 2026 Read the published version in Communications Earth & Environment → Version 1 posted You are reading this latest preprint version Abstract Climate models are increasingly used to inform water availability projections at regional scales. However, the models' own runoff sensitivities—the change in runoff per unit change of precipitation or temperature—are often biased, which can degrade their projections of runoff change. Specifically, models tend to underestimate the runoff decline in response to warming. Here, we conduct a comprehensive analysis with multiple observational datasets, two climate model generations, and large ensemble sampling of internal climate variability to assess these biases and to constrain future runoff projections across major river basins globally. For basins that can be robustly constrained by available observations, there is a tendency for stronger runoff declines than in the unconstrained case. The constrained projections thus indicate more severe impacts of climate change on water resources than indicated by direct climate model output. Earth and environmental sciences/Climate sciences/Climate change/Projection and prediction Earth and environmental sciences/Climate sciences/Hydrology Full Text Additional Declarations There is NO Competing Interest. Supplementary Files supplementary.pdf Supplementary figures Cite Share Download PDF Status: Published Journal Publication published 27 Jan, 2026 Read the published version in Communications Earth & Environment → 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. We do this by developing innovative software and high quality services for the global research community. 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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-5867679\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":410579610,\"identity\":\"60dfa7f1-d81e-4bd7-ac81-f8fe7d6ff3b8\",\"order_by\":0,\"name\":\"Hanjun Kim\",\"email\":\"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAElEQVRIiWNgGAWjYBACAwhO4GFgZj5w+E8FkMvM3ECkFva2xAM8Z0BaGAlrAYIEBgaeM8oHeNtAHAJazNnPHijm3ZEmozsjh+GA5LzaaP52oJYfFdtwarHsyUsw5j2Tw2N2I/fAAcNtx3NnHGZsYOw5cxu3ww7kGBjztlUAteQlHEjcdiy3AaiFmbENj5bzb2BacgwOHJxzLHc+QS03wLYAHXbmjMHBxoaa3A2EtbwxMJzblsZjdrwt4TDDsQO5G4FaDuL1y/kcM4O3bcn2ZoeZD39mqKnLnXf+8MEHPypwawECNgMkzmEweQCfeiBgfoDEqSOgeBSMglEwCkYiAAAt/WIVQQU9FwAAAABJRU5ErkJggg==\",\"orcid\":\"\",\"institution\":\"Cornell University\",\"correspondingAuthor\":true,\"prefix\":\"\",\"firstName\":\"Hanjun\",\"middleName\":\"\",\"lastName\":\"Kim\",\"suffix\":\"\"},{\"id\":410579611,\"identity\":\"4a7b2612-3a4c-4a87-a53b-eb57bdf1e0d4\",\"order_by\":1,\"name\":\"Flavio Lehner\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0003-4632-9701\",\"institution\":\"Cornell University\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Flavio\",\"middleName\":\"\",\"lastName\":\"Lehner\",\"suffix\":\"\"},{\"id\":410579612,\"identity\":\"beef7e62-ea9d-4d44-8690-b2532bb3f4b2\",\"order_by\":2,\"name\":\"Katherine Dagon\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0002-4518-8225\",\"institution\":\"NCAR\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Katherine\",\"middleName\":\"\",\"lastName\":\"Dagon\",\"suffix\":\"\"},{\"id\":410579613,\"identity\":\"1e14710e-86b1-4217-b88c-3d0faace3e5b\",\"order_by\":3,\"name\":\"David Lawrence\",\"email\":\"\",\"orcid\":\"https://orcid.org/0000-0002-2968-3023\",\"institution\":\"NSF NCAR\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"David\",\"middleName\":\"\",\"lastName\":\"Lawrence\",\"suffix\":\"\"},{\"id\":410579614,\"identity\":\"1040bb5a-f173-4bf1-9a6b-e880843d69b0\",\"order_by\":4,\"name\":\"Sean Swenson\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"National Center for Atmospheric Research\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Sean\",\"middleName\":\"\",\"lastName\":\"Swenson\",\"suffix\":\"\"},{\"id\":410579615,\"identity\":\"672071ac-9431-4cb3-b410-8e1237ba247f\",\"order_by\":5,\"name\":\"Andrew W. 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