Emergent climate projection discrepancies stem from spurious rainband

Emergent climate projection discrepancies stem from spurious rainband | 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 Emergent climate projection discrepancies stem from spurious rainband Robert Jnglin Wills, Pedro DiNezio This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7860860/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 As climate change unfolds, global climate models enable us to understand how anthropogenic influences are shaping the record-breaking climate anomalies occurring year after year. The distinctive pattern of anomalies in Pacific temperatures, with cooling in the east and southeast, and accelerated warming in the west, has received particular attention due to its widespread impacts on global and regional climate and because it departs from the more uniform warming anticipated by climate models. The apparent inability of climate models to simulate this warming pattern limits our ability to understand why it is occurring. Here we show that climate models’ Pacific warming pattern discrepancy stems from their simulation of a spurious Inter-Tropical Convergence Zone (ITCZ) rainband south of the equator—commonly referred to as the “double-ITCZ bias”—in a region that is dry year-round in observations. Models without a double-ITCZ bias produce anthropogenically forced warming patterns that more closely resemble observations as well as enhanced unforced decadal variability throughout the Indo-Pacific. We show that these features arise from the amplification of patterned climate anomalies when the equatorward propagation of temperature anomalies from the Southeast Pacific is unobstructed by a double ITCZ. Our findings suggest that observed tropical Pacific trends may contain a stronger forced component than previously recognized and that reducing the double-ITCZ bias is critical for improving the reliability of future climate projections. Earth and environmental sciences/Climate sciences/Climate change/Climate and Earth system modelling Earth and environmental sciences/Climate sciences/Climate change/Attribution Earth and environmental sciences/Climate sciences/Atmospheric science/Atmospheric dynamics Full Text Additional Declarations There is NO Competing Interest. Supplementary Files ITCZbiasscript.m Supplementary Software File: Main Script ITCZbiasfunctions.zip Supplementary Software File: Functions 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-7860860","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Physical Sciences - Article","associatedPublications":[],"authors":[{"id":529613002,"identity":"9ccea521-cf10-4beb-91f3-abb52cf399e3","order_by":0,"name":"Robert Jnglin 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