{"id":463308,"date":"2026-08-16T10:08:32","date_gmt":"2026-08-16T17:08:32","guid":{"rendered":"https:\/\/climatescience.press\/?p=463308"},"modified":"2026-08-16T10:08:34","modified_gmt":"2026-08-16T17:08:34","slug":"earths-hottest-climate-epoch-when-global-temperatures-hit-36c","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=463308","title":{"rendered":"Earth\u2019s Hottest Climate Epoch: When Global Temperatures Hit 36\u00b0C"},"content":{"rendered":"\n<figure class=\"wp-block-image size-large\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" width=\"723\" height=\"485\" data-attachment-id=\"463310\" data-permalink=\"https:\/\/climatescience.press\/?attachment_id=463310\" data-orig-file=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?fit=1168%2C784&amp;ssl=1\" data-orig-size=\"1168,784\" data-comments-opened=\"1\" data-image-meta=\"{&quot;credit&quot;:&quot;\\u00fe&quot;,&quot;caption&quot;:&quot;Signature: 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&quot;}\" data-image-title=\"0 Earth\u2019s Hottest Climate Epoch  When Global Temperatures Hit 36\u00b0C\" data-image-description=\"\" data-image-caption=\"&lt;p&gt;Signature: 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&lt;\/p&gt;\n\" data-large-file=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?fit=723%2C485&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?resize=723%2C485&#038;ssl=1\" alt=\"\" class=\"wp-image-463310\" srcset=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?resize=1024%2C687&amp;ssl=1 1024w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?resize=300%2C201&amp;ssl=1 300w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?resize=768%2C516&amp;ssl=1 768w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?resize=640%2C430&amp;ssl=1 640w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?w=1168&amp;ssl=1 1168w\" sizes=\"auto, (max-width: 723px) 100vw, 723px\" \/><figcaption class=\"wp-element-caption\">AI generated by Grok<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>The hottest climate intervals in Earth\u2019s more recent geological history (especially the Phanerozoic Eon, the last ~540 million years of complex life) reached global mean surface temperatures (GMST) of up to about 36 \u00b0C (97 \u00b0F).<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This is based on a 2024 reconstruction (Judd et al. in Science) that combined extensive proxy data with climate modeling for the past 485 million years. It shows GMST ranging from a low of ~11 \u00b0C to a high of ~36 \u00b0C\u2014hotter and more variable than many earlier estimates. Today\u2019s GMST is roughly 15 \u00b0C.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>The hottest epochs<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Cretaceous Hot Greenhouse \/ Cretaceous Thermal Maximum (roughly 90\u2013100 million years ago, peaking in the Turonian ~92 Ma):<\/strong> <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Frequently identified as the hottest period since the evolution of complex (non-microbial) life. Global average surface temperatures reached ~36 \u00b0C. Polar regions were ice-free, with high-latitude ocean temperatures sometimes exceeding 20\u201327 \u00b0C, and tropical temperatures potentially reaching 40+ \u00b0C in places. No major mass extinction is associated with this prolonged warmth.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Early Eocene Climatic Optimum (EECO) and related Hothouse state (~50\u201347 million years ago), including the Paleocene\u2013Eocene Thermal Maximum (PETM, ~56 Ma):<\/strong> <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">These were among the hottest of the last 66 million years. The broader Hothouse interval had temperatures more than 10 \u00b0C warmer than today. The PETM itself involved a rapid rise of ~5\u20138 \u00b0C (global mean estimates often put peak GMST in the low-to-mid 30s \u00b0C range, e.g., around 34 \u00b0C in some reconstructions). Polar regions supported subtropical vegetation (palms, crocodiles).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Earlier intervals (e.g., parts of the <strong>Paleozoic or the Neoproterozoic<\/strong>) also featured extreme warmth, and the <strong>Hadean Eon (Earth\u2019s first ~500 million years)<\/strong> involved a largely molten surface far hotter than any later climate. However, the Cretaceous peak is the standout for well-documented conditions with complex ecosystems.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Earlier intervals (e.g., parts of the <strong>Paleozoic or the Neoproterozoic)<\/strong> also featured extreme warmth, and the <strong>Hadean Eon (Earth\u2019s first ~500 million years) <\/strong>involved a largely molten surface <strong>far hotter than any later climate<\/strong>. However, the Cretaceous peak is the standout for well-documented conditions with complex ecosystems.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Atmospheric CO\u2082<\/strong> was the dominant long-term control on these temperatures (with a strong correlation across the Phanerozoic).<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Cretaceous Thermal Maximum:<\/strong> Commonly estimated well <strong>above 1,000 ppm<\/strong> (sometimes several times higher in various proxies and models; pre-industrial levels were ~280 ppm).<\/li>\n\n\n\n<li><strong>Early Eocene \/ PETM peak:<\/strong> Background levels were already high (hundreds to over 1,000 ppm); during the PETM spike, estimates reach as high as<strong> ~1,600\u20132,000+ ppm <\/strong>(some reconstructions go higher).<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">These ancient high-CO\u2082 greenhouse states were sustained over long geological timescales and supported diverse (if different) life.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The <strong>Phanerozoic Eon <\/strong>is the current and most recent geologic eon, spanning from approximately <strong>538.8 million years ago<\/strong> to the present.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It represents only about the last one-eighth of Earth\u2019s history but contains nearly all the fossil evidence of complex, macroscopic life (the name comes from <strong>Greek words meaning \u201cvisible life\u201d<\/strong>).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It is divided into three eras based primarily on major changes in life forms:<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th>Era<\/th><th>Time Span (approx.)<\/th><th>Key Features<\/th><\/tr><tr><td>Paleozoic (\u201cAncient Life\u201d)<\/td><td>539\u2013252 Ma<\/td><td>Cambrian explosion of animal diversity; colonization of land by plants, arthropods, and vertebrates; ends with the largest mass extinction (Permian\u2013Triassic)<\/td><\/tr><tr><td>Mesozoic (\u201cMiddle Life\u201d)<\/td><td>252\u201366 Ma<\/td><td>Age of reptiles\/dinosaurs; appearance of mammals, birds, and flowering plants; ends with the Cretaceous\u2013Paleogene extinction<\/td><\/tr><tr><td>Cenozoic (\u201cNew Life\u201d)<\/td><td>66 Ma\u2013present<\/td><td>Age of mammals; rise of modern ecosystems, grasses, and eventually humans; ongoing icehouse conditions<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\">These eras are further subdivided into 12 periods (Cambrian through Quaternary).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">During the<strong> Phanerozoic<\/strong>, Earth\u2019s climate has oscillated between<strong> long greenhouse (ice-free poles, high sea levels)<\/strong> and <strong>icehouse (polar ice sheets present) states<\/strong>. <strong>Global mean surface temperatures<\/strong> ranged from roughly <strong>11 \u00b0C to 36 \u00b0C<\/strong> according to recent reconstructions, with a strong overall correlation to atmospheric CO\u2082 levels.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Hot greenhouse peaks<\/strong> occurred in the <strong>early Paleozoic<\/strong>, parts of the <strong>Mesozoic (especially the Cretaceous Thermal Maximum)<\/strong>, and the<strong> early Cenozoic (Early Eocene Climatic Optimum and PETM)<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Major icehouse intervals<\/strong> include the <strong>late Paleozoic (Carboniferous\u2013Permian)<\/strong> and the current <strong>late Cenozoic icehouse (starting ~34 million years ago with Antarctic glaciation)<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>The Phanerozoic<\/strong> is the eon during which continents drifted into their modern configuration, <strong>oxygen levels became suitable for complex animal life<\/strong>, and the biosphere diversified dramatically\u2014despite <strong>multiple mass extinctions<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>Phanerozoic Eon Extinctions<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Phanerozoic Eon mass extinctions (spanning the last ~539 million years)<\/strong> include several major events that dramatically reduced biodiversity. The most prominent are the traditional <strong>\u201cBig Five\u201d<\/strong>, first highlighted by Raup and Sepkoski in the 1980s as statistically elevated extinction rates above background levels. Modern analyses show a continuum of extinction intensities rather than sharply distinct categories, but these five remain the largest post-Cambrian biodiversity crises.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">There are also many secondary or \u201csecond-order\u201d events (e.g., end-Capitanian, Toarcian, Cenomanian\u2013Turonian). Estimates of species\/genera loss vary by dataset and taxonomic level, but the figures below reflect widely cited approximations (mostly marine invertebrates, as the fossil record is strongest there).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>The Big Five Mass Extinctions<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><th>Rank (by severity)<\/th><th>Event<\/th><th>Timing<\/th><th>Approximate Losses<\/th><th>Primary Causes<\/th><th>Key Impacts<\/th><\/tr><tr><td>1 (most severe)<\/td><td><strong>End-Permian (\u201cGreat Dying\u201d \/ Permian\u2013Triassic)<\/strong><\/td><td>~251.9 Ma<\/td><td>~81\u201396% marine species; ~70% terrestrial vertebrates; ~57% families<\/td><td>Siberian Traps large igneous province (LIP) volcanism \u2192 massive CO\u2082\/SO\u2082 release, global warming, ocean anoxia\/acidification, euxinia<\/td><td>Ended the Paleozoic Era; wiped out trilobites, many corals, most synapsids; longest recovery (~5\u201310+ Myr)<\/td><\/tr><tr><td>2<\/td><td><strong>Late Ordovician (Ordovician\u2013Silurian)<\/strong><\/td><td>~445\u2013443 Ma<\/td><td>~85% marine species; ~57% genera; ~27% families<\/td><td>Glaciation of Gondwana \u2192 sea-level drop + cooling, followed by rapid warming\/anoxia<\/td><td>Mostly marine (brachiopods, trilobites, graptolites, etc.); two pulses<\/td><\/tr><tr><td>3<\/td><td><strong>Late Devonian (mainly Frasnian\u2013Famennian)<\/strong><\/td><td>~372\u2013359 Ma<\/td><td>~75% species; ~35\u201350% genera<\/td><td>Complex: possible ocean anoxia, cooling, sea-level changes, nutrient runoff from early forests, volcanism<\/td><td>Prolonged series of pulses; heavy impact on reef builders, placoderms, trilobites<\/td><\/tr><tr><td>4<\/td><td><strong>End-Triassic (Triassic\u2013Jurassic)<\/strong><\/td><td>~201.3 Ma<\/td><td>~70\u201380% species; ~48% genera; ~23% families<\/td><td>Central Atlantic Magmatic Province (CAMP) LIP volcanism \u2192 warming, ocean acidification<\/td><td>Cleared competitors for dinosaurs; ended many archosauromorphs, conodonts<\/td><\/tr><tr><td>5<\/td><td><strong>End-Cretaceous (Cretaceous\u2013Paleogene \/ K\u2013Pg)<\/strong><\/td><td>66 Ma<\/td><td>~75% species; ~40\u201350% genera<\/td><td>Chicxulub asteroid impact (+ possible contribution from Deccan Traps volcanism)<\/td><td>Non-avian dinosaurs, pterosaurs, ammonites, many marine reptiles extinct; started Cenozoic mammal radiation<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Other notable Phanerozoic events<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>End-Capitanian (~260 Ma)<\/strong> \u2014 Often linked to Emeishan Traps; significant but smaller than the main end-Permian pulse.<\/li>\n\n\n\n<li>T<strong>oarcian (Early Jurassic, ~183 Ma)<\/strong> and <strong>Cenomanian\u2013Turonian (~94 Ma) <\/strong>\u2014 Oceanic anoxic events tied to LIP volcanism.<\/li>\n\n\n\n<li><strong>Eocene\u2013Oligocene (~34 Ma)<\/strong> \u2014 <strong>Cooling and Antarctic glaciation<\/strong>; more of a turnover than a classic mass extinction.<\/li>\n\n\n\n<li><strong>Ongoing Holocene\/Anthropocene biodiversity crisis<\/strong> \u2014 Sometimes called a potential \u201csixth mass extinction\u201d due to human activities, though it has not yet reached the taxonomic severity of the Big Five.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Most Phanerozoic extinctions involved rapid climate and environmental change:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Large Igneous Province (LIP) volcanism<\/strong> \u2014 Dominant trigger for end-Permian, end-Triassic, and parts of others (releases greenhouse gases, causes warming\/acidification\/anoxia).<\/li>\n\n\n\n<li><strong>Bolide impacts <\/strong>\u2014 Clearly primary for the end-Cretaceous (Chicxulub); debated or secondary elsewhere.<\/li>\n\n\n\n<li><strong>Glaciation and sea-level change <\/strong>\u2014 Key for Late Ordovician and parts of Late Devonian.<\/li>\n\n\n\n<li>Proximate kill mechanisms often included ocean anoxia, acidification, temperature extremes, and habitat loss.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">These events repeatedly reset evolutionary trajectories, eliminating dominant groups and allowing survivors (and new lineages) to radiate into emptied ecological niches. The end-Permian was by far the most catastrophic, nearly ending complex life as we know it.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">_____________________________________________________________________________________<\/p>\n\n\n\n<p class=\"has-large-font-size wp-block-paragraph\"><strong>A 485-million-year history of Earth\u2019s surface temperature<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>\u201cA 485-million-year history of Earth\u2019s surface temperature\u201d <\/strong>is a major 2024 research paper published in Science (20 September 2024; DOI: 10.1126\/science.adk3705).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Led by Emily J. Judd (Smithsonian National Museum of Natural History \/ University of Arizona), with co-authors including Jessica E. Tierney, Daniel J. Lunt, Isabel P. Monta\u00f1ez, Brian T. Huber, Scott L. Wing, and Paul J. Valdes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">It produced<strong> PhanDA (Phanerozoic Data Assimilation)<\/strong>, a new reconstruction of global mean surface temperature (GMST) spanning most of the <strong>Phanerozoic Eon (the last 485 million years)<\/strong>. The team used <strong>data assimilation<\/strong> \u2014 a statistical method that combines:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Geological proxy data (e.g., oxygen isotopes from fossils and other paleoclimate indicators)<\/li>\n\n\n\n<li>Climate model simulations<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">This approach creates a more complete and consistent global temperature record than proxies or models alone.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>Key findings<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Temperature range:<\/strong> GMST varied between 11 \u00b0C and 36 \u00b0C (52\u201397 \u00b0F).\n<ul class=\"wp-block-list\">\n<li>Lowest: ~11 \u00b0C (Late Pleistocene glacial periods)<\/li>\n\n\n\n<li>Highest: ~36 \u00b0C (Turonian stage of the Late Cretaceous, ~90\u201394 million years ago)<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li>This <strong>range is larger than most previous reconstructions<\/strong> (which often suggested roughly 14\u201326 \u00b0C).<\/li>\n\n\n\n<li>Earth spent more time in warmer climate states than colder ones.<\/li>\n\n\n\n<li><strong>Tropical temperatures <\/strong>ranged from 22 \u00b0C to 42 \u00b0C, challenging the idea of a fixed upper limit on tropical heat.<\/li>\n\n\n\n<li><strong>Strong polar amplification<\/strong> (larger temperature changes at high latitudes) and a shallowing of the pole-to-equator temperature gradient as global temperatures rose.<\/li>\n\n\n\n<li><strong>Strong correlation with atmospheric CO\u2082:<\/strong> CO\u2082 is identified as the dominant long-term control on Phanerozoic climate.<\/li>\n\n\n\n<li>Apparent Earth system sensitivity of <strong>approximately ~8 \u00b0C per doubling of CO\u2082<\/strong> (higher than typical modern estimates that focus on shorter timescales).<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The reconstruction aligns well with independent Cenozoic temperature estimates, increasing confidence in the results for earlier periods.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This study provides one of the most detailed and rigorous long-term temperature curves available and is frequently cited in discussions of past greenhouse climates, climate sensitivity, and the role of CO\u2082 in Earth\u2019s history.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Published:<\/strong> Science (20 September 2024)<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>DOI:<\/strong> <a href=\"https:\/\/doi.org\/10.1126\/science.adk3705\">10.1126\/science.adk3705<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Authors:<\/strong> Emily J. Judd (Smithsonian National Museum of Natural History \/ University of Arizona), with co-authors including Jessica E. Tierney, Daniel J. Lunt, Isabel P. Monta\u00f1ez, Brian T. Huber, Scott L. Wing, and Paul J. Valdes.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Abstract<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">A long-term record of global mean surface temperature (GMST) provides critical insight into the dynamical limits of Earth\u2019s climate and the complex feedbacks between temperature and the broader Earth system. Here, we present PhanDA, a reconstruction of GMST over the past 485 million years, generated by statistically integrating proxy data with climate model simulations. PhanDA exhibits a large range of GMST, spanning 11\u00b0 to 36\u00b0C. Partitioning the reconstruction into climate states indicates that more time was spent in warmer rather than colder climates and reveals consistent latitudinal temperature gradients within each state. There is a strong correlation between atmospheric carbon dioxide (CO<sub>2<\/sub>) concentrations and GMST, identifying CO<sub>2<\/sub>&nbsp;as the dominant control on variations in Phanerozoic global climate and suggesting an apparent Earth system sensitivity of ~8\u00b0C.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The hottest climate intervals in Earth\u2019s more recent geological history (especially the Phanerozoic Eon, the last ~540 million years of complex life) reached global mean surface temperatures (GMST) of up to about 36 \u00b0C (97 \u00b0F).  <\/p>\n","protected":false},"author":121246920,"featured_media":463310,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","advanced_seo_description":"","jetpack_seo_html_title":"","jetpack_seo_noindex":false,"jetpack_seo_schema_type":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_wpcom_ai_launchpad_first_post":false,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"The hottest climate intervals in Earth's more recent geological history (especially the Phanerozoic Eon, the last ~540 million years of complex life) reached global mean surface temperatures (GMST) of up to about 36 \u00b0C (97 \u00b0F).","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"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":[691829997,691844728,691844729,691844730,691844731,691819222],"class_list":["post-463308","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-carbon-dioxide-co","tag-cretaceous-thermal-maximum","tag-greenhouse","tag-icehouse","tag-phanerozoic-eon","tag-temperature","fallback-thumbnail"],"jetpack_publicize_connections":[],"jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-1WwI","jetpack-related-posts":[{"id":314187,"url":"https:\/\/climatescience.press\/?p=314187","url_meta":{"origin":463308,"position":0},"title":"For Millions of Years Earth Temperatures Not Driven by\u00a0CO2","author":"uwe.roland.gross","date":"03\/28\/2024","format":false,"excerpt":"Atmospheric CO2 concentration is correlated weakly but negatively with linearly-detrended T proxies over the last 425 million years.","rel":"","context":"In \"ancient climate\"","block_context":{"text":"ancient climate","link":"https:\/\/climatescience.press\/?tag=ancient-climate"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/01868412.jpg?fit=1200%2C750&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/01868412.jpg?fit=1200%2C750&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/01868412.jpg?fit=1200%2C750&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/01868412.jpg?fit=1200%2C750&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/03\/01868412.jpg?fit=1200%2C750&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":303796,"url":"https:\/\/climatescience.press\/?p=303796","url_meta":{"origin":463308,"position":1},"title":"PETM Caused by Passing Star?","author":"uwe.roland.gross","date":"02\/22\/2024","format":false,"excerpt":"Paradigms and ruling theories drive scientists to looking for specific answers. And they tend to only see what they \u201cshine a light on.\u201d","rel":"","context":"In \"Climate change\"","block_context":{"text":"Climate change","link":"https:\/\/climatescience.press\/?tag=climate-change"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/02\/0Fotolia_44604161_Subscription_Monthly_M.jpg?fit=1200%2C800&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/02\/0Fotolia_44604161_Subscription_Monthly_M.jpg?fit=1200%2C800&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/02\/0Fotolia_44604161_Subscription_Monthly_M.jpg?fit=1200%2C800&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/02\/0Fotolia_44604161_Subscription_Monthly_M.jpg?fit=1200%2C800&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/02\/0Fotolia_44604161_Subscription_Monthly_M.jpg?fit=1200%2C800&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":344661,"url":"https:\/\/climatescience.press\/?p=344661","url_meta":{"origin":463308,"position":2},"title":"Media Confirms the Earth Is Not Abnormally Warm, Rather It Is in Its Coldest Period in 485 Million Years","author":"uwe.roland.gross","date":"09\/26\/2024","format":false,"excerpt":"Recently, many media outlets touted a new scientific study \u201cA 485-million-year history of Earth\u2019s surface temperature\u201d as proof that the current modest rise in temperature over the last 150 years is going to be catastrophic. The data and the methodology used strongly suggest that such claims are false.","rel":"","context":"In \"Bloomberg\"","block_context":{"text":"Bloomberg","link":"https:\/\/climatescience.press\/?tag=bloomberg"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/09\/0Screenshot-2024-09-26-090719-1024x836.png?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/09\/0Screenshot-2024-09-26-090719-1024x836.png?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/09\/0Screenshot-2024-09-26-090719-1024x836.png?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2024\/09\/0Screenshot-2024-09-26-090719-1024x836.png?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":385704,"url":"https:\/\/climatescience.press\/?p=385704","url_meta":{"origin":463308,"position":3},"title":"A 485-million-year history of bad science","author":"uwe.roland.gross","date":"06\/29\/2025","format":false,"excerpt":"A few days ago I published another analysis of mine, called\u00a0pHony Alarmism. Take a moment to read that if you haven\u2019t, because this is a sequel. Both are about a new study in Science Magazine yclept\u00a0\u201cA 485-million-year history of Earth\u2019s surface temperature\u201d, paywalled, of course.","rel":"","context":"In \"Atmospheric CO2\"","block_context":{"text":"Atmospheric CO2","link":"https:\/\/climatescience.press\/?tag=atmospheric-co2"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/06\/ChatGPT-Image-24.-Mai-2025-20_11_24-4.png?fit=1024%2C1024&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/06\/ChatGPT-Image-24.-Mai-2025-20_11_24-4.png?fit=1024%2C1024&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/06\/ChatGPT-Image-24.-Mai-2025-20_11_24-4.png?fit=1024%2C1024&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/06\/ChatGPT-Image-24.-Mai-2025-20_11_24-4.png?fit=1024%2C1024&ssl=1&resize=700%2C400 2x"},"classes":[]},{"id":245655,"url":"https:\/\/climatescience.press\/?p=245655","url_meta":{"origin":463308,"position":4},"title":"The Holocene Temperature Conundrum","author":"uwe.roland.gross","date":"02\/26\/2023","format":false,"excerpt":"Climate models are clearly not modeling natural climate change accurately, especially not orbital forcing. If you cannot model natural climate change, you have no idea what the human influence on climate is.","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-823.png?fit=1200%2C630&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-823.png?fit=1200%2C630&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-823.png?fit=1200%2C630&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-823.png?fit=1200%2C630&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/02\/image-823.png?fit=1200%2C630&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":253046,"url":"https:\/\/climatescience.press\/?p=253046","url_meta":{"origin":463308,"position":5},"title":"Another Day, Another CO2-Is-A-Climate-Driver Inconsistency","author":"uwe.roland.gross","date":"04\/15\/2023","format":false,"excerpt":"The observed climate sensitivity (CS) to a perturbation to Earth\u2019s Energy Imbalance (EEI) is, in a new study (Pauling et al., 2023), defined as -0.4\u00b0C per -9 W\/m\u00b2, or 0.044\u00b0C per W\/m\u00b2. These values were assessed using observations from Mt. Pinatubo.","rel":"","context":"In \"Climate effects\"","block_context":{"text":"Climate effects","link":"https:\/\/climatescience.press\/?tag=climate-effects"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/000_ARP2854576.jpg?fit=1200%2C800&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/000_ARP2854576.jpg?fit=1200%2C800&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/000_ARP2854576.jpg?fit=1200%2C800&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/000_ARP2854576.jpg?fit=1200%2C800&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2023\/04\/000_ARP2854576.jpg?fit=1200%2C800&ssl=1&resize=1050%2C600 3x"},"classes":[]}],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Earths-Hottest-Climate-Epoch-When-Global-Temperatures-Hit-36%C2%B0C.jpg?fit=1168%2C784&ssl=1","_links":{"self":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/463308","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=463308"}],"version-history":[{"count":36,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/463308\/revisions"}],"predecessor-version":[{"id":463349,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/463308\/revisions\/463349"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/media\/463310"}],"wp:attachment":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=463308"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=463308"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=463308"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}