{"id":280654,"date":"2023-09-27T12:01:31","date_gmt":"2023-09-27T10:01:31","guid":{"rendered":"https:\/\/climatescience.press\/?p=280654"},"modified":"2023-09-27T12:01:46","modified_gmt":"2023-09-27T10:01:46","slug":"summer-warming-1895-2023-in-u-s-cities-exaggerated-by-100-from-the-urban-heat-island-effect","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=280654","title":{"rendered":"Summer warming 1895-2023 in U.S. cities exaggerated by 100% from the urban heat island effect"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

<\/p>\n\n\n\n

From \u00a0Roy Spencer, PhD<\/a><\/p>\n\n\n\n

September 26th, 2023 by Roy W. Spencer, Ph. D.<\/em><\/strong><\/small><\/p>\n\n\n\n

We are now getting close to finalizing our methodology for computing the urban heat island (UHI) effect as a function of population density, and will be submitting our first paper for publication in the next few weeks. I\u2019ve settled on using the CONUS (Lower 48) U.S. region as a demonstration since that is where the most dense network of weather stations is. We are using NOAA\u2019s V4 of the GHCN monthly dataset.<\/p>\n\n\n\n

I\u2019ve previously described the methodology, where I use many thousands of closely-spaced station pairs to compute how temperature between stations change with population density at 10\u00d710 km resolution. This is done for 22 classes of 2-station average population density, and the resulting cumulative UHI curves are shown in Fig. 1.<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Fig. 1. Cumulative urban heat island effect in different multidecadal periods for the contiguous U.S. (CONUS), June\/July\/August, for GHCN monthly average ([Tmax+Tmin\/2]) temperatures calculated from regression of station-pair differences in temperature vs. population density in 22 classes of 2-station average population density. The number of station pairs used to compute these relationships ranges from 210,000 during 1880-1920 to 480,000 during 2000-2010.<\/p>\n\n\n\n

It is interesting that the spatial (inter-station temperature difference) UHI effect is always stronger in the homogenized GHCN data than in the raw version of those data in Fig. 1.\u00a0The very fact that there is a strong urban warming signal in the homogenized data necessitates that there must be a UHI impact on trends in those data. This is because the urban stations have grown substantially in the last 130 years.<\/em>\u00a0<\/p>\n\n\n\n

A recent\u00a0paper by Katata et al.<\/a>\u00a0demonstrates that the homogenization technique used by NOAA does not actually correct urban station trends to look like rural station trends. It does breakpoint analysis which ends up adjusting some stations to look like their neighbors, whether urban or rural. To the extend that spurious warming from UHI is gradual through time, it \u201clooks like\u201d global warming and will not be removed through NOAA\u2019s homogenization procedure. And since all classes of station (rural to urban) have undergone average population growth in the last 130 years, one cannot even assume that rural temperature trends are unaffected by UHI (see Fig. 2).<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Fig. 2. Cumulative growth in population density (PD) 1880-2015 at temperature monitoring stations in four classes of initial station urbanization, calculated by summing the average year-on-year increases in HYDE3.2 dataset population density at individual GHCN stations having at least two years of record in the 20\u00c2\u00b0N to 80\u00c2\u00b0N latitude band, for initial station PD of a 0 to 10, b 10 to 100, c 100 to 1,000, and d greater than 1,000 persons per sq. km initial station population density.<\/p>\n\n\n\n

The regression estimates of change in temperature with population density (dT\/dPD) used to construct the curves in Fig. 1 were used at each individual station in the U.S. and applied to the history of population density between 1895 and 2023. This produces a UHI estimate for each station over time. If I compute the area-average GHCN yearly summertime temperature anomalies and subtract out the UHI effect, I get a UHI-corrected estimate of how temperatures have changed without the UHI effect (Fig. 3).<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

Fig. 3. Lower-48 (CONUS) summertime U.S. temperature variations, 1895-2023, computed from GHCN \u201cadj\u201d (homogenized) data, versus those data adjusted for the urban heat island warming estimated from population density data.<\/p>\n\n\n\n

The data in Fig. 3 are from my 1 deg latitude\/longitude binning of station data, and then area-averaged. This method of area averaging for CONUS produces results extremely close to those produced at the NCDC \u201cClimate at a Glance\u201d website<\/a> (correlation = 0.996), which uses a high resolution (5 km) grid averaged to the 344 U.S. climate divisions then averaged to the 48 states then area averaged to provide a CONUS estimate.<\/p>\n\n\n\n

UHI Warming at Suburban\/Urban Stations is Large<\/strong><\/p>\n\n\n\n

The UHI influence averaged across all stations is modest: 24% of the trend, 1895-2023. This is because the U.S. thermometer network used in Version 4 of GHCN is dominated by rural stations.<\/p>\n\n\n\n

But for the average \u201csuburban\u201d (100-1,000 persons per sq. km) station, UHI is 52% of the calculated temperature trend, and 67% of the urban station trend (>1,000 persons per sq. km).<\/em> This means warming has been exaggerated by at least a factor of 2 (100%).<\/p>\n\n\n\n

This also means that media reports of record high temperatures in cities must be considered suspect, since essentially all those cities have grown substantially over the last 100+ years, and so has their urban heat island.<\/p>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

We are now getting close to finalizing our methodology for computing the urban heat island (UHI) effect as a function of population density, and will be submitting our first paper for publication in the next few weeks. I\u2019ve settled on using the CONUS (Lower 48) U.S. region as a demonstration since that is where the most dense network of weather stations is. We are using NOAA\u2019s V4 of the GHCN monthly dataset.<\/p>\n","protected":false},"author":121246920,"featured_media":280659,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","_crdt_document":"","advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1],"tags":[691823001,691818397,691823000,691823002,691821374],"class_list":{"0":"post-280654","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","6":"hentry","7":"category-uncategorized","8":"tag-1895-2023","9":"tag-noaa","10":"tag-summer-warming","11":"tag-u-s-cities","12":"tag-urban-heat-island-uhi-effect","14":"fallback-thumbnail"},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/01895-2023-CONUS-JJA-time-series-for-blog-post.jpg?fit=1280%2C720&ssl=1","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-1b0G","jetpack-related-posts":[{"id":378577,"url":"https:\/\/climatescience.press\/?p=378577","url_meta":{"origin":280654,"position":0},"title":"Our Urban Heat Island Paper Has Been Published","author":"uwe.roland.gross","date":"16\/05\/2025","format":false,"excerpt":"It took the better part of two years to satisfy the reviewers, but finally our paper\u00a0Urban Heat Island Effects in U.S. Summer Surface Temperature Data, 1895\u20132023\u00a0has been published in the AMS\u00a0Journal of Applied Meteorology and Climatology.","rel":"","context":"In \"GHCN stations\"","block_context":{"text":"GHCN stations","link":"https:\/\/climatescience.press\/?tag=ghcn-stations"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00glo-urban-heat-island-effect.webp?fit=1200%2C690&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00glo-urban-heat-island-effect.webp?fit=1200%2C690&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00glo-urban-heat-island-effect.webp?fit=1200%2C690&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00glo-urban-heat-island-effect.webp?fit=1200%2C690&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00glo-urban-heat-island-effect.webp?fit=1200%2C690&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":284165,"url":"https:\/\/climatescience.press\/?p=284165","url_meta":{"origin":280654,"position":1},"title":"New paper submission: Urban heat island effects in U.S. summer temperatures, 1880-2015","author":"uwe.roland.gross","date":"20\/10\/2023","format":false,"excerpt":"Urban heat islands concern both the temperature of various surfaces (streets, roofs, etc.) and the atmosphere.\u00a0The absorbed\u00a0heat during the day by the urban infrastructure is given away slowly \u2013 therefore also at night. From \u00a0Roy Spencer, PhD. October 19th, 2023 by Roy W. Spencer, Ph. D. After years of dabbling\u2026","rel":"","context":"In \"John Christy\"","block_context":{"text":"John Christy","link":"https:\/\/climatescience.press\/?tag=john-christy"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/0shutterstock_666649831-1024x629-1.png?fit=1024%2C629&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/0shutterstock_666649831-1024x629-1.png?fit=1024%2C629&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/0shutterstock_666649831-1024x629-1.png?fit=1024%2C629&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/10\/0shutterstock_666649831-1024x629-1.png?fit=1024%2C629&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":287175,"url":"https:\/\/climatescience.press\/?p=287175","url_meta":{"origin":280654,"position":2},"title":"Examples from our New UAH Urban Heat Island Dataset","author":"uwe.roland.gross","date":"08\/11\/2023","format":false,"excerpt":"Over 50% of the population now lives in urban areas, and that fraction is supposed to approach 70% by 2045. From Roy Spencer, PhD. November 7th, 2023 by Roy W. Spencer, Ph. D. Since few people who visit here will actually download and analyze data, I present some imagery of\u2026","rel":"","context":"In \"1880 through 2023\"","block_context":{"text":"1880 through 2023","link":"https:\/\/climatescience.press\/?tag=1880-through-2023"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/11\/00heatwaves.jpg?fit=1128%2C564&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/11\/00heatwaves.jpg?fit=1128%2C564&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/11\/00heatwaves.jpg?fit=1128%2C564&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/11\/00heatwaves.jpg?fit=1128%2C564&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/11\/00heatwaves.jpg?fit=1128%2C564&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":348954,"url":"https:\/\/climatescience.press\/?p=348954","url_meta":{"origin":280654,"position":3},"title":"Urban Heat Island Effects Have Not Yet Been Removed from Official GHCN Warming Trends","author":"uwe.roland.gross","date":"26\/10\/2024","format":false,"excerpt":"Our paper (co-authored by John Christy and Danny Braswell) on computing the urban heat island (UHI) effect as a function of population density (PD) is now in the final stages of review after a 3rd round of edits, and I\u2019m hopeful it will be accepted for publication soon.","rel":"","context":"In \"GHCN Warming Trends\"","block_context":{"text":"GHCN Warming Trends","link":"https:\/\/climatescience.press\/?tag=ghcn-warming-trends"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/10\/0Screenshot-2024-10-26-083344.png?fit=1200%2C851&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/10\/0Screenshot-2024-10-26-083344.png?fit=1200%2C851&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/10\/0Screenshot-2024-10-26-083344.png?fit=1200%2C851&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/10\/0Screenshot-2024-10-26-083344.png?fit=1200%2C851&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/10\/0Screenshot-2024-10-26-083344.png?fit=1200%2C851&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":378625,"url":"https:\/\/climatescience.press\/?p=378625","url_meta":{"origin":280654,"position":4},"title":"SHOCK CLIMATE REPORT! Urban Heat Islands Responsible for 65% of Global Warming","author":"uwe.roland.gross","date":"16\/05\/2025","format":false,"excerpt":"A new study from the University of Alabama in Huntsville addresses the question of how much the Urban Heat Island (UHI) effect is responsible for the higher temperatures at weather stations across the world. Dr. Roy Spencer and Dr. John Christy have spent several years developing a novel method that\u2026","rel":"","context":"In \"climactic \u201cgolden age\u201d\"","block_context":{"text":"climactic \u201cgolden age\u201d","link":"https:\/\/climatescience.press\/?tag=climactic-golden-age"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/05\/0Screenshot-2025-05-16-165630.png?fit=1200%2C671&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/05\/0Screenshot-2025-05-16-165630.png?fit=1200%2C671&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/05\/0Screenshot-2025-05-16-165630.png?fit=1200%2C671&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/05\/0Screenshot-2025-05-16-165630.png?fit=1200%2C671&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/05\/0Screenshot-2025-05-16-165630.png?fit=1200%2C671&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":281145,"url":"https:\/\/climatescience.press\/?p=281145","url_meta":{"origin":280654,"position":5},"title":"Summer in the City, 2023: Record Phoenix Warmth Not Reflected in Surrounding Weather Station Data","author":"uwe.roland.gross","date":"29\/09\/2023","format":false,"excerpt":"From \u00a0Roy Spencer, PhD. September 29th, 2023 by Roy W. Spencer, Ph. D. Ah, the 1960s. Even in 1966, before global warming was a thing, The Lovin\u2019 Spoonful was\u00a0singing about\u00a0(among other things) the unusual heat of the inner city. In fact, the heat caused by urban environments was discussed way\u2026","rel":"","context":"In \"2023\"","block_context":{"text":"2023","link":"https:\/\/climatescience.press\/?tag=2023"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00urbanheatisland.jpg?fit=1200%2C648&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00urbanheatisland.jpg?fit=1200%2C648&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00urbanheatisland.jpg?fit=1200%2C648&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00urbanheatisland.jpg?fit=1200%2C648&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/09\/00urbanheatisland.jpg?fit=1200%2C648&ssl=1&resize=1050%2C600 3x"},"classes":[]}],"_links":{"self":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/280654","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/users\/121246920"}],"replies":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=280654"}],"version-history":[{"count":5,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/280654\/revisions"}],"predecessor-version":[{"id":280662,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/280654\/revisions\/280662"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/media\/280659"}],"wp:attachment":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=280654"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=280654"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=280654"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}