Wood Romances

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Update (12/29/2024):  The paper I discuss below was retracted a couple days ago, citing failures in the peer-review process.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...

CO2 Coalition 's " Fact #8 " and " Fact #9 " want us to believe that more CO2 means more plant growth (Fact 8) and allow crops to feed more people globally (Fact 9). The claims here are not really new compared to other claims in this list of "facts," and we've already seen why these claims are misleading at best. We've seen in two posts ( here and here ) that increasing CO2 doesn't just cause greening through CO2 fertilization but also warming through the greenhouse effect. The latter increases heat stress for plants and limit their ability to make use of additional CO2 for photosynthesis. We've also seen here that CO2 Coalition just assumes that increases in corn yields are due to increased CO2 when the sources they cite actually attribute increases in crop yields to better hybrid corn and better technology. The logic of these facts is very similar. In "fact 9," we're shown a graph of grain production with CO2 and tempe...

  CO2 Coalition 's " Fact #29 ," " Fact #30 " and " Fact #31 " are essentially the same strawman attacks having to do with claims about droughts that nobody is actually saying. They basically observe here that there has been no change in droughts in the US, and droughts are declining globally. Here are the graphs they use to support this point. And yet who said otherwise? It's well-documented that warmer air holds more water, with water vapor increasing by ~7% for every 1 C warming. So on average, we should expect to see decreases in droughts as a global average. CO2 Coalition is attacking as strawman here. Climate scientists also observe that in more arid areas with less water availability, warming increases vapor pressure deficit (VPD) which should drive local and regional increases in the frequency and intensity of droughts (I cover more about this here ). This is observed in the American Southwest and in other areas around the world. In wetter...

CO2 Coalition 's " Fact #25 " claims that increasing CO2 causes moister soil. We're told that increasing CO2 concentrations means that plant stomata are open for shorter periods, so plants become more efficient (water use efficiency or WUE increases) and don't take as much water from soils. From this they claim that "CO2 fertilization has been linked to decreases in global fire, drought and heat waves." It's true that studies have shown that in some ecosystems, elevated CO2 has been linked to better water use efficiency (WUE) and improved soil moisture. But CO2 Coalition is being a bit selective in the information they present, even in the two examples they provide. In their first example, they cite research from CSIRO that showed that increasing CO2 has lead to a boost in green foliage in desert areas, but there are also secondary effects: "On the face of it, elevated CO2 boosting the foliage in dry country is good news and could assist forest...

CO2 Coalition 's " Fact 23 " claims that "CO2 increase is enhancing corn production" by a lot. This is such an astounding fact that CO2 Coalition devoted a whole sentence to defend its claim. "In the United States, corn production (bushels per acre) is steadily increasing as CO2 levels increase. This steady and continued increase cannot be explained simply by better technology." Here's the graph they show to support this from Nielson 2020 , which is an article posted on Purdue's website. The article says nothing about CO2. Instead, it says that corn yields were positively affected by several "miracles" that resulted in three stages of corn yields. Corn yields were stagnant from 1866-1936 until the rapid adoption of hybrid corn. Rapid adoption of double-cross hybrid corn by American farmers began in the late 1930's, in the waning years of the U.S. Dust Bowl and Great Depression. Within a very few years after that, the national yiel...