{"id":303796,"date":"2024-02-22T11:39:14","date_gmt":"2024-02-22T10:39:14","guid":{"rendered":"https:\/\/climatescience.press\/?p=303796"},"modified":"2024-02-22T11:39:16","modified_gmt":"2024-02-22T10:39:16","slug":"petm-caused-by-passing-star","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=303796","title":{"rendered":"PETM Caused by Passing Star?"},"content":{"rendered":"\n
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From Watts Up With That?<\/a><\/p>\n\n\n\n

Guest \u201cParadigm shift\u201d by David Middleton<\/p>\n\n\n

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Figure 1. Geologic time scale. (ICS<\/a>)<\/figcaption><\/figure>\n<\/div>\n\n\n

The Paleocene Eocene Thermal Maximum (PETM) was a geologically brief spike in temperatures, during the warmest climatic episode of the Cenozoic Era.<\/p>\n\n\n\n

We are often told that the warmth of the Early Paleogene was driven by CO2<\/sub>; and that the cool-down from the Late Paleogene, into the Neogene and Quaternary Periods was driven by a draw-down of atmospheric CO2<\/sub>; however there is scant evidence for this hypothesis[1<\/a>][2<\/a>]. Despite the paucity of geological evidence, the notion of a CO2<\/sub>-driven climate has apparently become a paradigm.<\/p>\n\n\n\n

This paradigm didn\u2019t exist in the 1970\u2019s.<\/p>\n\n\n\n

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Suggestion that changing carbon dioxide content of the atmosphere could be a major factor in climate change dates from 1861, when it was proposed by British physicist John Tyndall.<\/p>\n\n\n\n

[\u2026]<\/p>\n\n\n\n

Unfortunately we cannot estimate accurately changes of past CO2<\/sub> content of either atmosphere or oceans, nor is there any firm quantitative basis for estimating the the magnitude of drop in carbon dioxide content necessary to trigger glaciation.  Moreover the entire concept of an atmospheric greenhouse effect is controversial, for the rate of ocean-atmosphere equalization is uncertain<\/strong><\/em>.Dott, Robert H. & Roger L. Batten. Evolution of the Earth. McGraw-Hill, Inc. Second Edition 1976. p. 441.<\/em><\/p>\n<\/blockquote>\n\n\n\n

While methods of estimating past CO2<\/sub>\u00a0levels have improved, the Early Paleogene is still poorly understood, with estimates ranging from 300 to 3,500 ppm.<\/p>\n\n\n\n

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Figure 2a. Cenozoic temperature (Zachos et al., 2001) and CO2<\/sub>\u00a0reconstructions. Mmarine pCO2<\/sub>\u00a0(foram boron \u03b411<\/sup>B,\u00a0alkenone<\/a>\u00a0\u03b413<\/sup>C), atmospheric CO2<\/sub>\u00a0from plant stomata (green and yellow diamonds with red outlines), Mauna Loa instrumental CO2<\/sub>\u00a0(thick red line) and Cenozoic temperature change from\u00a0benthic foram<\/a>\u00a0\u03b418<\/sup>O (light gray line). Paleocene Eocene Thermal Maximum (PETM), Early Eocene Climatic Optimum (EECO), Middle Eocene Climatic Optimum (MECO), Middle Miocene Climatic Optimum (MMCO).<\/figcaption><\/figure>\n\n\n
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Figure 2b. Legend for Figure 3a.<\/figcaption><\/figure>\n<\/div>\n\n\n

The recent publication by\u00a0The Cenozoic CO2<\/sub>\u00a0Proxy Integration Project (CenCO2<\/sub>PIP) Consortium<\/a>\u00a0failed to significantly reduce Paleogene uncertainty despite claims to the contrary.<\/p>\n\n\n\n

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Figure 3. Cenozoic Era CO2<\/sub>\u00a0and temperature.
(The Cenozoic CO2<\/sub>\u00a0Proxy Integration Project (CenCO2<\/sub>PIP) Consortium<\/a>)<\/figcaption><\/figure>\n\n\n\n

Why geologists are supposed to avoid paradigms<\/h3>\n\n\n
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Figure 4. You only find what you\u2019re looking for. (JC at the National Press Club<\/a>)<\/figcaption><\/figure>\n<\/div>\n\n\n

When I was studying geology, way back when The Ice Age Cometh<\/a><\/em> in the 1970\u2019s<\/a>, we were taught to avoid getting hooked on paradigms or \u201cruling theories\u201d. Geology, as a science, has very few unique solutions<\/a>. This is why we were were taught to embrace Chamberlin\u2019s Method of Multiple Working Hypotheses<\/a>. I have to assume that either this is no longer the case or that homage must be paid to the current paradigm in order to get published. The CenCO2<\/sub>PIP Consortium embraced it BIG TIME.<\/p>\n\n\n\n

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The consortium\u2019s members did not collect new data; rather, they came together to sort through published studies to assess their reliability, based on evolving knowledge. They excluded some that that they found outdated or incomplete in the light of new findings, and recalibrated others to account for the latest analytical techniques. Then they calculated a new 66-million-year curve of CO2 versus temperatures based on all the evidence so far, coming to a consensus on what they call \u201cearth system sensitivity.\u201d By this measure, they say, a doubling of CO2<\/sub> is predicted to warm the planet a whopping 5 to 8 degrees C.<\/strong>Columbia Climate School: Climate, Earth and Society<\/a><\/p>\n<\/blockquote>\n\n\n\n

Paradigms and ruling theories drive scientists to looking for specific answers. And they tend to only see what they \u201cshine a light on.\u201d The current paradigm is that CO2<\/sub> has driven climate change over the Phanerozoic Eon (the past ~540 MY).<\/p>\n\n\n\n

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  1. The Paleocene-Eocene was, on average, 4\u201315 \u00b0C warmer than today.<\/li>\n\n\n\n
  2. Atmospheric CO2<\/sub>\u00a0was very likely in the 450-600 ppm range.<\/li>\n\n\n\n
  3. Modern climate models would require 4,500 ppm CO2<\/sub>\u00a0to simulate the Paleocene-Eocene temperature range.<\/li>\n<\/ol>\n\n\n\n

    Therefore the equilibrium climate sensitivity must be 5-8 \u00b0C per doubling of atmospheric CO2<\/sub>, rather than the observation-supported 2.3 \u00b0C per doubling<\/a> (a transient climate response of only 1.2-1.6 \u00b0<\/em>C).<\/p>\n\n\n\n

    It never seems to occur to them that something completely different drove climate change over geologic time.<\/p>\n\n\n\n

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    1. <\/li>\n<\/ol>\n\n\n\n

      \u201cAnd now for something completely different\u2026\u201d<\/h3>\n\n\n\n
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      Earth\u2019s Orbit Mysteriously Altered by Chance Encounter Million of Years Ago<\/h3>\n\n\n\n

      SPACE<\/a> 19 February 2024<\/p>\n\n\n\n

      By MICHELLE STARR<\/a><\/p>\n\n\n\n

      A grazing encounter between the Solar System and a passing star could once have changed Earth\u2019s orbit enough to wreak havoc on the climate, new research has found.<\/p>\n\n\n\n

      Around 56 million years ago, at the boundary between the Paleocene and Eocene, Earth\u2019s temperature warmed by up to 8 \u00b0C (14.4 \u00b0F).<\/p>\n\n\n\n

      This has always been a bit of a puzzle \u2013 but planetary scientist Nathan Kaib of the Planetary Science Institute and astrophysicist Sean Raymond of the Laboratory of Astrophysics of Bordeaux suggest a chance encounter may have been the culprit.<\/p>\n\n\n\n

      Their simulations show that a star passing by the Solar System could have introduced enough disruption to planetary orbits to nudge Earth slightly off course.<\/p>\n\n\n\n

      \u201cOne reason this is important is because the geologic record shows that changes in the Earth\u2019s orbital eccentricity accompany fluctuations in the Earth\u2019s climate,\u201d Kaib says<\/a>.<\/p>\n\n\n\n

      \u201cIf we want to best search for the causes of ancient climate anomalies, it is important to have an idea of what Earth\u2019s orbit looked like during those episodes.\u201d<\/p>\n\n\n\n

      [\u2026]<\/p>\n\n\n\n

      Kaib and Raymond wanted to know if a passing star could have a similar effect, even from a significant distance. Their work focused on a single known event. Some 2.8 million years ago, a Sun-like star called HD 7977<\/a> passed the Solar System, potentially so closely that it flew inside the Oort Cloud.<\/p>\n\n\n\n

      [\u2026]<\/p>\n\n\n\n

      HD 7977 is one star, and the only flyby we can confidently identify. But scientists have estimated that a star passes by within 50,000 astronomical units every million years or so, and within 10,000 astronomical units every 20 million years or so.<\/p>\n\n\n\n

      This means that it\u2019s entirely possible that a passing star has affected Earth\u2019s climate in the past \u2013 and may even have played a role in the thermal maximum.<\/p>\n\n\n\n

      [\u2026]Science Alert<\/a><\/p>\n<\/blockquote>\n\n\n\n

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