{"id":255618,"date":"2023-05-02T17:02:36","date_gmt":"2023-05-02T15:02:36","guid":{"rendered":"https:\/\/climatescience.press\/?p=255618"},"modified":"2023-05-02T17:02:38","modified_gmt":"2023-05-02T15:02:38","slug":"urbanization-effects-on-ghcn-temperature-trends-part-v-tmin-warming-at-u-s-vs-non-u-s-stations","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=255618","title":{"rendered":"Urbanization Effects on GHCN Temperature Trends, Part V: Tmin Warming at U.S. vs. non-U.S. Stations"},"content":{"rendered":"\n
\"\"<\/figure>\n\n\n\n

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

From Roy Spencer, PhD.<\/a><\/p>\n\n\n\n

May 1st, 2023 by Roy W. Spencer, Ph. D.<\/small><\/p>\n\n\n\n

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

In my last post<\/a> (Part IV) I showed how urbanization (as measured by population density) affects GHCN monthly-average Tmax and Tmin near-surface air temperatures during the warm season in the Northern Hemisphere. We are utilizing a technique<\/a> that recognizes<\/a> rural thermometer sites can experience large spurious warming with very small increases in population density, as has been known for over 50 years.<\/p>\n\n\n\n

The urban heat island (UHI) effects on Tmin averaged 3.5 times as large as on Tmax, an unsurprising result and qualitatively consistent with previous studies. Also, I showed that the homogenization procedure NOAA uses to adjust the Tmax and Tmin temperatures caused greater UHI effects compared to raw (unadjusted) data, a result I cannot explain.<\/p>\n\n\n\n

Again I will emphasize that these UHI warming results are based upon spatial<\/em> comparisons between neighboring stations, and do not say anything quantitative about how much urbanization effects have spuriously warmed long-term temperature trends<\/em> over land. That is indeed the goal of our study, but we have not reached that point in the analysis yet.<\/p>\n\n\n\n

Here in Part V of my series on UHI I just want to show the difference between U.S. and non-U.S. stations, in this cased for adjusted (homogenized) Tmin data. This is shown in the following two plots, which are the same except the second plot has a logarithmic scale in population density.<\/p>\n\n\n\n

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

The non-U.S. stations have a more rapid rise in UHI warming at very low population densities than the U.S. stations do, but less rapid warming at high population densities. Possible reasons for this include country differences in thermometer siting and differences in waste heat generation. I\u2019m sure you can think of other possible reasons.<\/p>\n\n\n\n

As can be seen most (over 80%) of the GHCN 2-station matchups come from the U.S. Other countries have considerably fewer 2-station matchups, for example Canada (7.8% of the Northern Hemisphere total), Japan (4.7%), Turkey (2.8%), South Korea (1.3%), and China (1.1%). These low totals are not necessarily due to a lack of stations, but to a lack of station pairs within 150 km and 300 m elevation of each other needed for my current method of analysis.<\/p>\n","protected":false},"excerpt":{"rendered":"

The urban heat island (UHI) effects on Tmin averaged 3.5 times as large as on Tmax, an unsurprising result and qualitatively consistent with previous studies. <\/p>\n","protected":false},"author":121246920,"featured_media":255625,"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":[691819263],"class_list":{"0":"post-255618","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","6":"hentry","7":"category-uncategorized","8":"tag-urban-heat-island-effect","10":"fallback-thumbnail"},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/05\/00urbanheatisland.jpg?fit=1640%2C885&ssl=1","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-14uS","jetpack-related-posts":[{"id":255147,"url":"https:\/\/climatescience.press\/?p=255147","url_meta":{"origin":255618,"position":0},"title":"Urbanization Effects on GHCN Temperature Trends, Part IV: UHI Effects on Tmax and Tmin","author":"uwe.roland.gross","date":"04\/28\/2023","format":false,"excerpt":"This is part 4 of my series on quantifying Urban Heat Island (UHI) effects on surface air temperatures as reported in the monthly GHCN datasets produced by NOAA.","rel":"","context":"In \"GHCN temperature trends\"","block_context":{"text":"GHCN temperature trends","link":"https:\/\/climatescience.press\/?tag=ghcn-temperature-trends"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/00UHI-May-June-July-Tmax-Tmin-2.jpg?fit=864%2C960&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":403226,"url":"https:\/\/climatescience.press\/?p=403226","url_meta":{"origin":255618,"position":1},"title":"The Hottest Summer Days in the U.S. Have Barely Warmed in the Last 40 Years","author":"uwe.roland.gross","date":"09\/19\/2025","format":false,"excerpt":"The total warming of the hottest 3 days in each summer month averaged across 400 mostly-airport weather stations is only 1.2 deg. F over 40 years.","rel":"","context":"In \"\u201cHeat waves\u201d\"","block_context":{"text":"\u201cHeat waves\u201d","link":"https:\/\/climatescience.press\/?tag=heat-waves-2"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/09\/00Screenshot-2025-09-19-103751.png?fit=1098%2C783&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/09\/00Screenshot-2025-09-19-103751.png?fit=1098%2C783&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/09\/00Screenshot-2025-09-19-103751.png?fit=1098%2C783&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/09\/00Screenshot-2025-09-19-103751.png?fit=1098%2C783&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/09\/00Screenshot-2025-09-19-103751.png?fit=1098%2C783&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":441393,"url":"https:\/\/climatescience.press\/?p=441393","url_meta":{"origin":255618,"position":2},"title":"The Urban Heat Island and Urban Cool Island: A Few Examples for U.S. Major Metropolitan Areas","author":"uwe.roland.gross","date":"04\/25\/2026","format":false,"excerpt":"One important aspect of the population density-based research was that the UHI effect on U.S. warming trends largely disappeared after about 1960. We used population density for that study because there are global gridpoint datasets of PD at approximately 10 km spatial resolution going back centuries. So, it was a\u2026","rel":"","context":"In \"daily maximum temperature (Tmax)\"","block_context":{"text":"daily maximum temperature (Tmax)","link":"https:\/\/climatescience.press\/?tag=daily-maximum-temperature-tmax"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/04\/0-The-Urban-Heat-Island-and-Urban-Cool-Island-A-Few-Examples-for-U.S.-Major-Metropolitan-Areas.jpg?fit=1168%2C784&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/04\/0-The-Urban-Heat-Island-and-Urban-Cool-Island-A-Few-Examples-for-U.S.-Major-Metropolitan-Areas.jpg?fit=1168%2C784&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/04\/0-The-Urban-Heat-Island-and-Urban-Cool-Island-A-Few-Examples-for-U.S.-Major-Metropolitan-Areas.jpg?fit=1168%2C784&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/04\/0-The-Urban-Heat-Island-and-Urban-Cool-Island-A-Few-Examples-for-U.S.-Major-Metropolitan-Areas.jpg?fit=1168%2C784&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/04\/0-The-Urban-Heat-Island-and-Urban-Cool-Island-A-Few-Examples-for-U.S.-Major-Metropolitan-Areas.jpg?fit=1168%2C784&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":243950,"url":"https:\/\/climatescience.press\/?p=243950","url_meta":{"origin":255618,"position":3},"title":"Evidence that Statistical Adjustments and Urbanization Spuriously Warm Temperature Trends","author":"uwe.roland.gross","date":"02\/09\/2023","format":false,"excerpt":"Urbanization Effects on GHCN Temperature Trends, Part II: Evidence that Homogenization Spuriously Warms Trends","rel":"","context":"Similar post","block_context":{"text":"Similar post","link":""},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-360.png?fit=990%2C765&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-360.png?fit=990%2C765&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-360.png?fit=990%2C765&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-360.png?fit=990%2C765&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":280654,"url":"https:\/\/climatescience.press\/?p=280654","url_meta":{"origin":255618,"position":4},"title":"Summer warming 1895-2023 in U.S. cities exaggerated by 100% from the urban heat island effect","author":"uwe.roland.gross","date":"09\/27\/2023","format":false,"excerpt":"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. 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