Wood Romances

One of the frequently repeated tropes in climate contrarian circles is the supposed " line of death " at 150 ppm below which, we're told, all photosynthesis stops, so all plant life dies and there's a mass extinction of life on Earth. CO2 Coalition loves to trot out this trope to claim that, since CO2 became as low as 170 ppm during the glacial cycles of the Quaternary, we were dangerously close to a mass extinction. They claim we're still "CO2 starved." They also tell us that Berner's 2001 CO2 models shows "an alarming downward trend toward CO2 starvation."  We're then apparently supposed to be thankful for fossil fuel emissions that have saved us from perhaps the extinction of all life on earth. The DOE report, authored by the "climate working group" (CWG), tones down this rhetoric a bit, but it's essentially the same claim with slightly different numbers: "At the end of the last glaciation CO2 levels had fallen to...

The Keeling Curve I sometimes hear claims that our measurements of CO2 concentrations, especially as recovered in ice core data, are unreliable indicators of variability in CO2 concentrations, often stating that CO2 may have varied by far more than scientists are letting us know about. The implication is that scientists are covering up evidence for the variability of atmospheric CO2 concentrations to sell a narrative that humans are responsible for the increase in CO2. There are at least two forms of lines of argument here, one arguing that ice core data is unreliable and the other arguing that other measurements of CO2 contradict the ice core record. 1. Zbigniew Jaworowski It appears that even in the 1990s there were attempts by contrarian scientists to undermine the reliability of the empirical data extracted from ice cores to reconstruct background CO2 concentrations over the last several hundred thousand years. One such paper, Jaworowski 1994[1], argued that the CO2 data was unreli...

The Paleocene–Eocene Thermal Maximum (PETM) was a period of time beginning about  56 million years ago. Temperatures increased by 5–8°C[2][4] due to a large excursion of biogenic carbon. Temperatures increased extremely rapidly, and the perturbation of the carbon cycle led to ocean acidification and a mass extinction of benthic foraminifera. The warming event occurred suddenly, geologically speaking, perhaps in as little as 10,000 years[12], making it one the most rapid warming events detected in the Phanerozoic. The extreme warmth of the PETM lasted less than 220,000 years before returning to "normal" Eocene levels. The rapid warming warming associated with the PETM makes it a good analogue to current warming, so I think it would be helpful to cover this event as well as provide a bibliography for further reading on the subject. The PETM is also one among many examples in geologic history where it is clear that GHGs were driving global warming. CO2 led (and drove) the warmin...

Note: 1/15/2024. Graphs are updated to include 2024 when available. You sometimes hear that, at least on certain time scales, CO2 and global temperature (GMST) don't correlate very well or even that the two go in opposite directions. The implication drawn from this is that CO2 can't be the primary driver of climate changes. What I want to show here is that this claim is categorically false. On virtually all time scales in the Phanerozoic, CO2 and GMST correlate very well, especially when taking into consideration that GMST correlates with the log of CO2.  The best way for me to demonstrate this point is to simply show the correlation. Where I can, I convert CO2 to forcings (using RF = 5.35*ln(CO2/280)) and and plot CO2 forcings on the x-axis and GMST on the y-axis. This gives us two advantages: first, it allows us to calculate the r^2 for that correlation, and second, the slope of the correlation gives us an indication of sensitivity - that is, the temperature response to chang...

Update (12/29/2024):  The paper I discuss below was retracted a couple days ago, citing failures in the peer-review process. "Subsequent to acceptance of this paper, the rigor and quality of the peer-review process for this paper was investigated and confirmed to fall beneath the high standards expected by Applications in Engineering Science . After review by additional expert referees, the Editor-in-Chief has lost confidence in the validity of the paper and has decided to retract." A paper published earlier this year is the latest in the long history of attempts to show that CO2 is already "saturated" in the atmosphere, and therefore increased CO2 cannot cause any more warming. The latest in a series of these kinds of papers from Kubicki et al 2024[1] attempts to make this point by modeling the atmosphere in a couple different experiments. The result of their experiments suggested to them that we should question whether "additionally emitted CO2 in the atmosp...

Along with the publication of Emily Judd's reconstruction[1] of global temperatures, she and her team compiled an up-to-date reconstruction of CO2 concentrations from proxy data. I shared in a previous post how this new reconstructions shows a CO2 and GMST as well-correlated on geologic time scales, with GMST increasing by ~8 C for 2xCO2. Her CO2 reconstruction is another step forward for paleoclimate because it makes use of a growing database of proxy evidence, much of which is being compiled at the Paleo CO2 project . For the Paleozoic and Mesozoic, Judd's reconstruction followed Foster et al 2017 [2] pretty closely, especially during the Paleozoic, but she also included additional data from Witkowski et al 2018[4][3]. Differences between Judd's and Foster's reconstruction had to do with different ways of site and time averaging and updates from Witkowski's study. During the Cenozoic, she followed more recent work by Rae et al 2021 [5] which agrees closely with t...