{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T19:55:45Z","timestamp":1790625345591,"version":"4.1.0"},"reference-count":71,"publisher":"National Academy of Sciences","issue":"40","license":[{"start":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T00:00:00Z","timestamp":1790553600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100012166","name":"MOST | National Key Research and Development Program of China","doi-asserted-by":"publisher","award":["2023YFE0122300"],"award-info":[{"award-number":["2023YFE0122300"]}],"id":[{"id":"10.13039\/501100012166","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2026,10,6]]},"abstract":"<jats:p>\n                    Urban densification is widely promoted to improve land-use efficiency and curb sprawl, but it can reduce winter sunlight in old urban cores, an important dimension of urban livability. Although three-dimensional (3D) urban form is known to shape sunlight availability, most studies focus on present-day conditions, typical urban forms, or planning scenarios. How much sunlight has been lost through recent redevelopment, particularly in legacy neighborhoods, remains unclear. Here we quantify densification-induced winter direct-sunlight loss across the old urban cores of 77 large cities in mainland China. We map winter-solstice direct-sunlight access at 5-m resolution using 3D building data and city-specific solar geometry, comparing the observed 2020 built environment with a counterfactual (CF) circa-1990 height field for legacy buildings. The CF uses city-specific empirical height caps and is evaluated against historically documented block-scale cases. Over three decades, densification reduced sunlight across 36% of old-core areas on average, with mean duration in affected areas declining from 5.37 to 3.75 h. Around 7% of the area (603 km\n                    <jats:sup>2<\/jats:sup>\n                    ) shifted from sufficient to insufficient sunlight, while 17.7% (1,525 km\n                    <jats:sup>2<\/jats:sup>\n                    ) fell below the 2-h threshold by 2020. Mean losses ranged from 1.08 to 2.46 h across cities, affecting approximately 16 million first-floor residents, including around 0.61 million exposed to severe losses of 3 to 6 h. Losses were more extensive in cities with shorter baseline sunlight, greatest in second-tier cities, and steeper at higher latitudes. These findings provide a scalable basis for sunlight-sensitive urban renewal and height regulation.\n                  <\/jats:p>","DOI":"10.1073\/pnas.2624733123","type":"journal-article","created":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T19:02:56Z","timestamp":1790622176000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":0,"title":["Three decades of urban densification reduced winter direct sunlight access across China\u2019s old urban cores"],"prefix":"10.1073","volume":"123","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2713-3810","authenticated-orcid":false,"given":"Kechao","family":"Wang","sequence":"first","affiliation":[{"name":"Department of Land Management, Department of Land Management, School of Public Affairs, Zhejiang University","place":["Hangzhou, China"]},{"id":[{"id":"https:\/\/ror.org\/00cvxb145","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Urban Design and Planning, University of Washington","place":["Seattle"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiangyuan","family":"Wu","sequence":"additional","affiliation":[{"name":"Department of Land Management, Department of Land Management, School of Public Affairs, Zhejiang University","place":["Hangzhou, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Liutao","family":"Chen","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/00cvxb145","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Urban Design and Planning, University of Washington","place":["Seattle"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0343-6147","authenticated-orcid":false,"given":"Tzu-Hsin Karen","family":"Chen","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/00cvxb145","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Urban Design and Planning, University of Washington","place":["Seattle"]},{"id":[{"id":"https:\/\/ror.org\/00cvxb145","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Environmental and Occupational Health Sciences, University of Washington","place":["Seattle"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2493-0694","authenticated-orcid":false,"given":"Wu","family":"Xiao","sequence":"additional","affiliation":[{"name":"Department of Land Management, Department of Land Management, School of Public Affairs, Zhejiang University","place":["Hangzhou, China"]},{"id":[{"id":"https:\/\/ror.org\/00a2xv884","id-type":"ROR","asserted-by":"publisher"}],"name":"Inclusive and Smart Urban-Rural Governance Lab, Zhejiang University","place":["Hangzhou, China"]},{"id":[{"id":"https:\/\/ror.org\/00a2xv884","id-type":"ROR","asserted-by":"publisher"}],"name":"Zhejiang Key Laboratory of Agricultural Remote Sensing and Information Technology, Zhejiang University","place":["Hangzhou, China"]},{"id":[{"id":"https:\/\/ror.org\/00a2xv884","id-type":"ROR","asserted-by":"publisher"}],"name":"Land Academy for National Development, Zhejiang University","place":["Hangzhou, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2026,9,28]]},"reference":[{"key":"e_1_3_4_1_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.landurbplan.2019.05.001"},{"key":"e_1_3_4_2_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.cities.2014.09.006"},{"key":"e_1_3_4_3_2","doi-asserted-by":"publisher","DOI":"10.1038\/s44284-024-00120-x"},{"key":"e_1_3_4_4_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(21)01209-5"},{"key":"e_1_3_4_5_2","doi-asserted-by":"publisher","DOI":"10.1080\/09603123.2019.1572105"},{"key":"e_1_3_4_6_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.sleh.2017.03.005"},{"key":"e_1_3_4_7_2","doi-asserted-by":"publisher","DOI":"10.5664\/jcsm.3780"},{"key":"e_1_3_4_8_2","doi-asserted-by":"publisher","DOI":"10.3390\/ijerph18199980"},{"key":"e_1_3_4_9_2","doi-asserted-by":"publisher","DOI":"10.1098\/rstb.2016.0246"},{"key":"e_1_3_4_10_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.smrv.2009.11.002"},{"key":"e_1_3_4_11_2","volume-title":"Workplace (Health, Safety and Welfare) Regulations 1992","author":"Great Britain, Health and Safety Executive","year":"1993","unstructured":"Great Britain, Health and Safety Executive, Workplace (Health, Safety and Welfare) Regulations 1992 (Great Britain, Health and Safety Executive, 1993)."},{"key":"e_1_3_4_12_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jum.2024.02.002"},{"key":"e_1_3_4_13_2","doi-asserted-by":"publisher","DOI":"10.1080\/03071375.2012.692505"},{"key":"e_1_3_4_14_2","doi-asserted-by":"publisher","DOI":"10.3390\/buildings15224053"},{"key":"e_1_3_4_15_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-025-10282-w"},{"key":"e_1_3_4_16_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41893-020-0521-x"},{"key":"e_1_3_4_17_2","doi-asserted-by":"publisher","DOI":"10.1038\/s42949-024-00170-z"},{"key":"e_1_3_4_18_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.342.6156.310-a"},{"key":"e_1_3_4_19_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.1235823"},{"key":"e_1_3_4_20_2","doi-asserted-by":"publisher","DOI":"10.5334\/bc.123"},{"key":"e_1_3_4_21_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.2201780119"},{"key":"e_1_3_4_22_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.rse.2020.112096"},{"key":"e_1_3_4_23_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.landurbplan.2024.105043"},{"key":"e_1_3_4_24_2","doi-asserted-by":"publisher","DOI":"10.1177\/0739456X05285119"},{"key":"e_1_3_4_25_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ufug.2015.09.003"},{"key":"e_1_3_4_26_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.habitatint.2021.102503"},{"key":"e_1_3_4_27_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.cities.2024.105682"},{"key":"e_1_3_4_28_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.scs.2022.104224"},{"key":"e_1_3_4_29_2","doi-asserted-by":"publisher","DOI":"10.1038\/s41597-023-02240-w"},{"key":"e_1_3_4_30_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.landurbplan.2025.105466"},{"key":"e_1_3_4_31_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.scs.2024.106011"},{"key":"e_1_3_4_32_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.scs.2023.104499"},{"key":"e_1_3_4_33_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ufug.2018.02.013"},{"key":"e_1_3_4_34_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.landurbplan.2023.104874"},{"key":"e_1_3_4_35_2","doi-asserted-by":"publisher","DOI":"10.3390\/ijgi10090583"},{"key":"e_1_3_4_36_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.scs.2025.106133"},{"key":"e_1_3_4_37_2","first-page":"53","article-title":"Combinational shadow index for building shadow extraction in urban areas from Sentinel-2A MSI imagery","volume":"78","author":"Sun G.","year":"2019","unstructured":"G. Sun , Combinational shadow index for building shadow extraction in urban areas from Sentinel-2A MSI imagery. Int. J. Appl. Earth Obs. Geoinf. 78, 53\u201365 (2019).","journal-title":"Int. J. Appl. Earth Obs. Geoinf."},{"key":"e_1_3_4_38_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.isprsjprs.2020.07.016"},{"key":"e_1_3_4_39_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.rse.2020.111945"},{"key":"e_1_3_4_40_2","doi-asserted-by":"publisher","DOI":"10.1080\/22797254.2023.2293163"},{"key":"e_1_3_4_41_2","doi-asserted-by":"publisher","DOI":"10.1007\/978-3-319-46466-4_49"},{"key":"e_1_3_4_42_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.landurbplan.2021.104217"},{"key":"e_1_3_4_43_2","doi-asserted-by":"publisher","DOI":"10.1007\/s10900-018-0522-0"},{"key":"e_1_3_4_44_2","doi-asserted-by":"publisher","DOI":"10.3354\/cr00882"},{"key":"e_1_3_4_45_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.compenvurbsys.2021.101655"},{"key":"e_1_3_4_46_2","article-title":"A preliminary exploration of the cooling effect of tree shade in urban landscapes","volume":"92","author":"Yu Q.","year":"2020","unstructured":"Q. Yu , A preliminary exploration of the cooling effect of tree shade in urban landscapes. Int. J. Appl. Earth Observ. Geoinf. 92, 102161 (2020).","journal-title":"Int. J. Appl. Earth Observ. Geoinf."},{"key":"e_1_3_4_47_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.scs.2023.105026"},{"key":"e_1_3_4_48_2","doi-asserted-by":"publisher","DOI":"10.1080\/09613218.2016.1159850"},{"key":"e_1_3_4_49_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.buildenv.2019.106503"},{"key":"e_1_3_4_50_2","unstructured":"V. Ar\u00e9valo J. Gonz\u00e1lez J. Valdes G. Ambrosio \u201cDetecting shadows in QuickBird satellite images\u201d in International Society for Photogrammetry and Remote Sensing Mid-term Symposium 2006: Remote Sensing: From Pixels to Processes N. Kerle A. Skidmore Eds. (International Institute for Geo-Information Science and Earth Observation Enschede The Netherlands 2006) pp. 330\u2013335."},{"key":"e_1_3_4_51_2","doi-asserted-by":"publisher","DOI":"10.3390\/rs11202348"},{"key":"e_1_3_4_52_2","unstructured":"A. Bill N. Mohajeri J.-L. Scartezzini \u201c3D model for solar energy potential on buildings from urban LiDAR data\u201d in Eurographics Workshop on Urban Data Modelling and Visualisation (2016) pp. 1\u20136. https:\/\/diglib.eg.org:443\/handle\/10.2312\/udmv20161420. Accessed 6 March 2026."},{"key":"e_1_3_4_53_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.scitotenv.2016.09.102"},{"key":"e_1_3_4_54_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.enbuild.2018.07.064"},{"key":"e_1_3_4_55_2","doi-asserted-by":"publisher","DOI":"10.1038\/d41586-019-01238-y"},{"key":"e_1_3_4_56_2","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0318665","article-title":"A study on the evolution of original sites of fortifications from the perspective of Historic Urban Landscape: Cases of Paris, Beijing, and Moscow","volume":"20","author":"Xu M.","year":"2025","unstructured":"M. Xu, H. Zhu, A study on the evolution of original sites of fortifications from the perspective of Historic Urban Landscape: Cases of Paris, Beijing, and Moscow. PLoS ONE 20, e0318665 (2025).","journal-title":"PLoS ONE"},{"key":"e_1_3_4_57_2","doi-asserted-by":"publisher","DOI":"10.1111\/1468-2427.12604"},{"key":"e_1_3_4_58_2","doi-asserted-by":"publisher","DOI":"10.1080\/13658816.2018.1511793"},{"key":"e_1_3_4_59_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1944-8287.2010.01077.x"},{"key":"e_1_3_4_60_2","doi-asserted-by":"publisher","DOI":"10.1007\/s40471-014-0014-4"},{"key":"e_1_3_4_61_2","unstructured":"Ministry of Construction of the People\u2019s Republic of China Planning and design standards for urban residential areas. https:\/\/www.cacp.org.cn\/zlbzgf\/5171.jhtml. Accessed 2 July 2026."},{"key":"e_1_3_4_62_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.landusepol.2017.02.024"},{"key":"e_1_3_4_63_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.cities.2017.01.002"},{"key":"e_1_3_4_64_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.cities.2019.05.006"},{"key":"e_1_3_4_65_2","doi-asserted-by":"publisher","DOI":"10.1088\/1748-9326\/ab9be3"},{"key":"e_1_3_4_66_2","doi-asserted-by":"publisher","DOI":"10.5194\/essd-16-5357-2024"},{"key":"e_1_3_4_67_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.rse.2019.111510"},{"key":"e_1_3_4_68_2","unstructured":"Open spatial demographic data and research. WorldPop. https:\/\/www.worldpop.org\/. Accessed 6 March 2026."},{"key":"e_1_3_4_69_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.scib.2019.12.007"},{"key":"e_1_3_4_70_2","unstructured":"Global Monitoring Laboratory Team Solar calculator\u2014NOAA global monitoring laboratory. https:\/\/gml.noaa.gov\/grad\/solcalc\/index.html. Accessed 6 March 2026."},{"key":"e_1_3_4_71_2","unstructured":"K. Wang X. Wu L. Chen T.-H. K. Chen W. Xiao Three decades of urban densification reduced winter direct sunlight access across China\u2018s old urban cores. Zenodo. https:\/\/doi.org\/10.5281\/zenodo.22285364. Deposited 3 September 2026."}],"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.2624733123","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T19:03:45Z","timestamp":1790622225000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/10.1073\/pnas.2624733123"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,28]]},"references-count":71,"journal-issue":{"issue":"40","published-print":{"date-parts":[[2026,10,6]]}},"alternative-id":["10.1073\/pnas.2624733123"],"URL":"https:\/\/doi.org\/10.1073\/pnas.2624733123","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,28]]},"assertion":[{"value":"2026-07-16","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-08-25","order":2,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-09-28","order":3,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e2624733123"}}