Phanerozoic Climate

While blogs are useful as an online journal of reflections on the scientific literature on climate change, they are not as useful for systematically organizing various posts on a single topic. I'm going to try to get around that by using pages. As I add more content to the blog that is related to Phanerozoic climate change, I will edit this page to make it easier to see the content I've written in a more systematic fashion. The links below take you to posts providing more information about the subject.

Scientific Literature on Phanerozoic Climate

  1. The scientific literature assessing the correlation between CO2 and global temperatures goes back over 20 years. In one of my first posts, I attempted to survey the most significant studies evaluating CO2 and temperatures across the phanerozoic, with both model (like GEOCARBIII and GEOCARBSULF) and proxy reconstructions of CO2 with various temperature reconstructions (like Royer and Scotese). Much of this survey has to do with the development of the GEOCARB model for CO2 and comparing that model to either reconstructions of global temperatures or the extent of glaciation. CO2 proxies are not reliable for Cambrian through Silurian CO2.
  2. In my view, the literature took a big step forward with a study showing temperature variability from CO2 proxy and solar forcings for the last 420 million years. The proxy evidence for CO2, plotted as radiative forcing and corrected for solar evolution gives a better analysis of how the major forcings affected temperature from the Devonian on.
  3. Recently, a paper co-authored by Mills (co-authored by Christopher Scotese) demonstrated that there is good correlation between CO2 proxies and global temperatures throughout the last 420 million years. CO2 models are not yet able to reproduce the accuracy of the proxy reconstructions, but they are constantly improving as our understanding of the major geologic forcings affecting CO2 (the long-term climate cycle, plate tectonics, etc) develops. "By compiling independent proxy records of global average surface temperature and atmospheric CO2 concentration for the Phanerozoic, we have shown that when accounting for the solar flux, long-term Phanerozoic surface temperature changes can be clearly related to variations in the CO2 greenhouse (Fig. 6). CO2 appears to be a primary driver of climate on geological timescales (e.g. Royer et al., 2004)."

Contrarian Misuses of the Phanerozoic Climate Literature

  1. Contrarian blogs and political think tanks frequently promote the idea that CO2 and temperature do not correlate across geologic history. Almost all of these attempts rely on the GEOCARBIII model in Berner 2001 along with an old schematic from Scotese for global temperatures. Both the CO2 model and temperature schematic are about 20 years out of date. I document numerous failed attempts at showing now correlation in one post, including failures even to graph the data properly (some plot the CO2 model on the wrong time scale. 
  2. In another post, I show how plotting the CO2 model properly with temperature confirms the broad correlation between CO2 and temperature.
  3. There are many other attempts by contrarians to evaluate the paleoclimate evidence but fail to understand it or represent it accurately. For instance, Steve Koonin misrepresented the GEOCARBIII model as a proxy reconstruction instead of a climate model. This is a minor point, perhaps, but it's telling in a book that is (overly) critical of climate models.
  4. Gregory Wrightone is a geologist who spent most of his career working for the fossil fuel industry, but now he's leading CO2 Coalition. His book, Inconvenient Facts, specializes in misrepresenting the paleoclimate literature. I have a two part review of his book. The first part covers his views of CO2 and paleoclimate. The second part covers his false claims about temperature. Both of these reviews refer to his false claims related to Phanerozoic climate.
  5. Some claim that plant life can't survive below 150 ppm CO2, but paleoclimate evidence from the Early Permian shows that vegetation can survive below 150 ppm CO2, though these conditions likely heavily favor C4 plants.



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