Responding to the CO2 Coalition's "Facts #6 and #7" on CO2 Concentrations on Geologic Time Scales

CO2 Coalition's "fact #6" and "fact #7" are essentially identical, and both are largely just a rehash of statements made in previous "facts." Here we're told that "our current geologic period, the Quaternary, has seen the lowest average levels of carbon dioxide since the Precambrian." To support this claim, they took the data from the climate model in Berner 2001 and averaged all the CO2 concentration values for each Geologic period, ignoring the confidence intervals and the length of the period, and plotted the following graph. Note that each geologic period is shown as if they were the same length.


As I've already shared, CO2 proxies often paints a somewhat different picture from Berner 2001's climate model. The model has been updated several times since 2001, but the CO2 Coalition appears to be completely unaware of this. Here again is the proxy evidence we have for CO2. It's pretty sparse before the proliferation of vascular plants on land. 


CO2 Coalition's chart is also pretty disingenuous. The Quaternary has lasted only about 2.6 million years, while the Cretaceous lasted 79 million years. It's hardly a valid comparison to treat the Cretaceous and Quaternary equally. In fact, their "fact #7" nicely illustrates how short the Quaternary has been compared to other Geologic periods.


Has there been a Quaternary-length time frame in which CO2 levels dropped below the average CO2 concentrations of the Quaternary? Probably. During the Permian (which lasted 47 million years), CO2 levels dropped to ~100 ppm for about 1 million years in the early Permian and were likely ~200 ppm or lower for a longer period of time. The graph below shows how this time period compares to the range of CO2 values during the Quaternary glaciations (indicated to the right of the graph).


Of course, pretty much none of this has any relevance to current warming. The mere fact that throughout the Phanerozoic CO2 levels averaged higher than the Quaternary doesn't mean that the current increase in CO2 isn't harmful to human civilization. We built our civilizations during the relatively stable climate of the Holocene (the last 11,700 years of the Quaternary), where CO2 levels varied between 260 and 280 ppm. Human carbon emissions have increased this by 50% to 420 ppm, and the climate is quickly responding. Global climate is headed into territory that the Earth has not seen in the last 3 million years. Its the disruption of stability that is harmful, not the absolute value of CO2.

Comments

Post a Comment

Popular posts from this blog

The Marketing of Alt-Data at Temperature.Global

Image
Temperature.Global (12-month running average, sort of) A few years ago, I started seeing people post links to a new dataset for global temperatures at a website called temperature.global. There are at least four unique features of this dataset. First, the website claims to update global temperature in near real time. Second, every year in the dataset averages below "normal." Third, there is absolutely no transparency regarding their methodology (those who administer it are anonymous, most of the data is hidden, and much of their methodology is unclear). And fourth, what is disclosed about their methodology reveals that what they are calculating is not the Earth's surface temperature. Description of Temperature.Global If you go to the temperature.global website, it becomes almost immediately apparent that this website has little concern for transparency. The website is hosted by Parler (the alternative social network), which if nothing else is pretty odd. There are no name
Read more

Are Scientists and Journalists Conspiring to Retract Papers?

Image
Dr. Roger Pielke, Jr has published two posts recently having to do with extreme weather and the IPCC. In the first post , he expresses frustration over an apparently inevitable retraction of a paper on extreme weather. The paper is Alimonti et al 2022 (A22) published in The European Physical Journal Plus (EPJP)[1]. I became aware of this paper about a year ago; it was not a good paper and was not particularly influential; it received almost no attention except for a brief period of time when the usual blogs promoted it, and then after SkyNews in Australia publicized this study as demonstrating there is no climate emergency. In the second post , Pielke summarized what he believes the IPCC's position is on extreme weather, and here he refers again to this previous paper. He declares that he believes that popular and scientific treatments of extreme weather have become far mor extreme than the position taken by the IPCC. According to him, "with the exception perhaps of only extr
Read more

Tropical Cyclone Trends

Image
In a previous post , I covered the distinction between detection and attribution. These are normally considered sequentially. First you detect a signal above natural variability, then you examine if some portion of that signal can be attributed to human activity. The previous post shows that the two are statistically independent from each other, so there is no need to limit attribution studies to signals that are detectable above natural variability. This distinction and clarification I think is important in discussions of tropical cyclone trends. While trends are clear since 1980, the longer term record (since ~1850-1900) is less clear due to selection biases arising from our increasing ability to detect tropical cyclones. This makes detection difficult long term, but that doesn't necessarily mean that scientists can't also examine ways in which human activity is affecting tropical cyclone trends. Detection in the Satellite Record (Since 1980) The satellite record provides us
Read more