{"id":413203,"date":"2025-11-14T09:49:37","date_gmt":"2025-11-14T08:49:37","guid":{"rendered":"https:\/\/climatescience.press\/?p=413203"},"modified":"2025-11-14T09:49:40","modified_gmt":"2025-11-14T08:49:40","slug":"new-study-suggests-co2-levels-were-necessarily-as-high-as-today-10000-years-ago","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=413203","title":{"rendered":"New Study Suggests CO2 Levels Were Necessarily as High as Today 10,000 Years Ago"},"content":{"rendered":"\n
\"Animated<\/figure>\n\n\n\n

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

From No Trick Zone<\/a><\/p>\n\n\n\n

By Kenneth Richard<\/a><\/em><\/p>\n\n\n\n

It is widely acknowledged that the enhanced CO2 fertilization effect due to the modern rise in atmospheric CO2 is the predominant driver of the dramatic increases in global greening, or \u201cgross primary production\u201d (GPP). Global greening attribution estimates for CO2 fertilization range from 70% (Zhu et al., 2016<\/a><\/strong>) to 86% (Haverd et al., 2020<\/a><\/strong>).<\/p>\n\n\n\n

As noted in a new study<\/a><\/strong>, Earth is thought to have been much greener than today during the Early Holocene (10,000 years ago), with over 50% more forest cover.<\/p>\n\n\n\n

Since an increase in the CO2 concentration is recognized as the most dominant factor in greening, it would not<\/em> be consistent with what we know about the requisite physics of GPP (CO2 residence time, water and nutrient availability, the diminishing returns effect of CO2 fertilization) to assume the lower levels of CO2 (under 300 ppm) suggested by Antarctic ice core records are accurate reflections of the actual CO2 levels from 10,000 years ago.<\/p>\n\n\n\n

To achieve the high levels of Early Holocene greenness, CO2 levels needed to be as high or higher than today\u2019s 420 ppm at that time too. The Earth could not have been as green as it was back then with atmospheric CO2 concentrations of only 280 ppm or less.<\/p>\n\n\n\n

\u201cEmploying Mitscherlich\u2019s Law, the research models the global GPP response to increasing CO\u2082, based on the mean value of eight different long-term GPP datasets. It illustrates a diminishing return of vegetation associated with rising CO\u2082, as additional factors such as nutrient and water availability impose constraints on the fertilization effect. Due to this diminishing return the average residence time of CO\u2082 in the atmosphere increases significantly with higher GPP values. High CO\u2082 levels, similar to today\u2019s, were therefore necessary for comparable GPP during green periods like 10,000 years ago. A CO\u2082 concentration of 280 ppm would only be possible if nature\u2019s response to CO\u2082 were fundamentally different from what we observe today, with other constraining factors exceptionally more favorable.\u201d<\/h6>\n\n\n\n

Interestingly, a chart from the paper uses the IPCC\u2019s carbon cycle estimations to asses nature\u2019s CO2 emission rates have risen 4 times more (+44 GtC\/year net, or from +166 GtC\/year in 1750 to +210 GtC\/year in 2022) than human emissions rates have (from 0 GtC\/year in 1750 to +11 GtC\/year today). Since Earth\u2019s natural sinks don\u2019t distinguish between natural vs. human CO2 emissions, the bulk of the modern increase in CO2 can be said to have been derived from rising natural CO2 emissions, not human activity.<\/p>\n\n\n\n

\"A
Image Source: Schrijver, 2025<\/a><\/strong><\/figcaption><\/figure>\n\n\n\n

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

It is widely acknowledged that the enhanced CO2 fertilization effect due to the modern rise in atmospheric CO2 is the predominant driver of the dramatic increases in global greening, or \u201cgross primary production\u201d (GPP). Global greening attribution estimates for CO2 fertilization range from 70% (Zhu et al., 2016) to 86% (Haverd et al., 2020).<\/p>\n","protected":false},"author":121246920,"featured_media":413209,"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":"Discover how historical CO2 levels may have driven Earth's greening 10,000 years ago, impacting vegetation growth and forest cover.","jetpack_seo_html_title":"High CO2 Levels Were Essential for Early Holocene Greening","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":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":true,"token":"eyJpbWciOiJodHRwczpcL1wvY2xpbWF0ZS1zY2llbmNlLnByZXNzXC93cC1jb250ZW50XC91cGxvYWRzXC8yMDI1XC8xMVwvMFNjcmVlbnNob3QtMjAyNS0xMS0xNC0wOTQ2MjYtMTAyNHg2NDMucG5nIiwidHh0IjoiTmV3IFN0dWR5IFN1Z2dlc3RzIENPMiBMZXZlbHMgV2VyZSBOZWNlc3NhcmlseSBhcyBIaWdoIGFzIFRvZGF5IDEwLDAwMCBZZWFycyBBZ28iLCJ0ZW1wbGF0ZSI6ImhpZ2h3YXkiLCJmb250IjoiIiwiYmxvZ19pZCI6MTU1ODEyNDQ5fQ.cc209hc-k1DStlpeZIWpIfJIB_kjvKi3eD1C3bHyk4EMQ"},"version":2},"jetpack_post_was_ever_published":false},"categories":[1],"tags":[691829997,691820981,691819784,691822252],"class_list":{"0":"post-413203","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","6":"hentry","7":"category-uncategorized","8":"tag-carbon-dioxide-co","9":"tag-co2-fertilization-2","10":"tag-early-holocene","11":"tag-global-greening","13":"fallback-thumbnail"},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/11\/0Screenshot-2025-11-14-094626.png?fit=1417%2C890&ssl=1","jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-1Juz","jetpack-related-posts":[{"id":408566,"url":"https:\/\/climatescience.press\/?p=408566","url_meta":{"origin":413203,"position":0},"title":"The Carbon Conundrum: Did Earth\u2019s Greenest Periods Demand High CO2?","author":"uwe.roland.gross","date":"16\/10\/2025","format":false,"excerpt":"The Earth is getting greener.\u00a0Satellite data confirms a significant increase in vegetation\u2014or\u00a0global greening\u2014over the past century, with\u00a0Gross Primary Production\u00a0(GPP)\u00a0\u2013the rate of carbon fixation by plants\u2013 rising by over 30% since 1900.","rel":"","context":"In \"carbon dioxide (CO\u2082)\"","block_context":{"text":"carbon dioxide (CO\u2082)","link":"https:\/\/climatescience.press\/?tag=carbon-dioxide-co%e2%82%82"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/10\/0AQPEQUHb8v5OSbuEnSiIYBybhbr-xR917mtPL7k1G-Idpp9u_wntK0-2Nq99l5mFtAWL0GkSQtCDmbrV6-judC6NWcCuBYl1_1XtojnbZaUMP8T2B3Rh4sEKVmcl_v8o-1.jpeg?fit=1200%2C824&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/10\/0AQPEQUHb8v5OSbuEnSiIYBybhbr-xR917mtPL7k1G-Idpp9u_wntK0-2Nq99l5mFtAWL0GkSQtCDmbrV6-judC6NWcCuBYl1_1XtojnbZaUMP8T2B3Rh4sEKVmcl_v8o-1.jpeg?fit=1200%2C824&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/10\/0AQPEQUHb8v5OSbuEnSiIYBybhbr-xR917mtPL7k1G-Idpp9u_wntK0-2Nq99l5mFtAWL0GkSQtCDmbrV6-judC6NWcCuBYl1_1XtojnbZaUMP8T2B3Rh4sEKVmcl_v8o-1.jpeg?fit=1200%2C824&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/10\/0AQPEQUHb8v5OSbuEnSiIYBybhbr-xR917mtPL7k1G-Idpp9u_wntK0-2Nq99l5mFtAWL0GkSQtCDmbrV6-judC6NWcCuBYl1_1XtojnbZaUMP8T2B3Rh4sEKVmcl_v8o-1.jpeg?fit=1200%2C824&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2025\/10\/0AQPEQUHb8v5OSbuEnSiIYBybhbr-xR917mtPL7k1G-Idpp9u_wntK0-2Nq99l5mFtAWL0GkSQtCDmbrV6-judC6NWcCuBYl1_1XtojnbZaUMP8T2B3Rh4sEKVmcl_v8o-1.jpeg?fit=1200%2C824&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":346897,"url":"https:\/\/climatescience.press\/?p=346897","url_meta":{"origin":413203,"position":1},"title":"New Antarctic Greening Study Wilfully Blind to CO2 Fertilization","author":"uwe.roland.gross","date":"15\/10\/2024","format":false,"excerpt":"The study published in\u00a0Nature Geoscience, titled \u201cSustained Greening of the Antarctic Peninsula Observed from Satellites,\u201d focuses on the observed increase in vegetation, particularly moss-dominated ecosystems, on the Antarctic Peninsula (AP). 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