Contrarian CO2 and Temperature Graphs: Really?

Example 1: CO2 and Temperature

I frequently hear that climate scientists only consider the last 150 years of history (since the beginning of the instrumental record), and if we paid better attention to geology, we would realize one or more of several things: 1) CO2 doesn't correlate with temperature or doesn't affect global temperatures, 2) climate changes are normal, so there's no danger with current warming, 3) most of the earth's history has been warmer than today, so a bit of warming would be good or 4) CO2 levels have been declining to dangerous levels for millions of years, and thankfully we burned fossil fuels to save the planet from CO2 starvation. None of these claims are true, and none have any basis in geologic evidence. I have several posts here showing the correlation between CO2 and temperature and/or glaciation. So where do people get this idea? One of the chief sources of misinformation is crappy graphs like the one above (Example 1).

Early Examples

Example 1 above does not come from the peer-reviewed literature - at least not as is. It contains two components: 1) the CO2 portion comes from the GEOCARBIII climate model published by Berner 2001.[1] There is nothing particularly wrong with this source, other than it's over 20 years old, and many more studies have been published that improve our understanding of how CO2 has fluctuated in the past. However, Example 1 lacks the uncertainty estimate, which is quite large, especially before the Permo-Carboniferous Glaciation. The scale of Berner's graph is RCO2, which is the ratio of CO2 in the past to preindustrial CO2. 

Climate Model of CO2 from Berner 2001

Another missing component here is an accounting of solar evolution. The Sun was only about 70% as bright when the earth was formed as it is now. Over geologic time, the earth has experienced a gradual increase in solar radiation, increasing in a roughly linear fashion. This means that over geologic history the CO2 threshold for glaciation has declined. The Earth could sustain glaciation at higher CO2 levels 550 million years ago than it can today. Example 1 fails to take this into consideration. But this is just the CO2 portion of the graph. The temperature graph is much worse. 

Still another issue has to do with the expected correlation between global surface temperature and CO2 concentrations. The relationship is not linear. Rather, the doubling of CO2 causes a linear increase in radiative forcing. That is, the relationship between CO2 and radiative forcing is logarithmic. The relationship between an increase in radiative forcing and temperature is linear. So by plotting CO2 concentrations with temperatures, we would not expect a linear correlation between the two. To show that, you would need to plot the natural log of CO2.

The temperature graph in Example 1 (and all of these examples) is not published in peer-reviewed literature. It's from Christopher Scotese, an expert in reconstructions of the positions of continents over the Earth's history. But this temperature graph here doesn't really qualify as a reconstruction. It's basically just a schematic built on a now outdated hypothesis that the earth periodically oscillated between "ice-house" conditions and "hot-house" conditions with very little time spent at intermediate temperatures. Over time Scotese has updated his schematic, and he has even improved the scale. Instead of going from 12 to 22 C it was changed from 10 to 25 C in later versions. But notice how the person who made this graph chose to make the temperature scale take up only the bottom 40% of the graph while the CO2 scale takes up the whole graph. This seems to be a deliberate attempt to obscure the correlation between the two graphs. But we're just getting started. Here's another, later version of the same graph.

Example 2

This graph makes some improvements over the previous version. Uncertainty estimates have been added to the CO2 portion of the graph, and the temperature portion has been updated to a newer version of the Scotese graph with an improved scale. However, it's still largely based on the outdated ice-house vs hothouse model that is pretty much worthless for this kind of comparison, and again it's only using the lower 40% of the graph for the temperature scale. But the real problem here is the arrows that exploit the faults in the temperature schematic and the lack of resolution in the CO2 climate model. The apparent discrepancy at 150 million years ago is well within the uncertainties of the GEOCARBIII model, so it's not an issue. The end-Ordovician glaciation is a more apparent problem. But what this illustrates is the failure of the author of this graph to read Berner 2001. Berner specifically points out that the model does not contain the resolution to pick up the Ordovician glaciation.

This type of modeling is incapable of delimiting shorter term CO2 fluctuations (Paleocene-Eocene boundary, late Ordovician glaciation) because of the nature of the input data which is added to the model as 10 my or longer averages. Thus, exact values of CO2, as shown by the standard curve, should not be taken literally and are always susceptible to modification. Nevertheless, the overall trend remains. This means that over the long term there is indeed a correlation between CO2 and paleotemperature, as manifested by the atmospheric greenhouse effect.[1] 

There are many more iterations of these early graphs, some with the uncertainty estimates for CO2 and some without, some using more recent versions of the Scotese schematic, but all of these have several faults in common. They 1) ignore solar evolution, 2) rely on a CO2 climate model that lacks sufficient resolution, 3) are based on an outdated schematic of temperatures, and 4) suffer from issues of scale. But we're still not done.

Newer Examples

Example 3

As best I can tell, Example 3 comes from Nasif Nahle and popularized by Patrick Moore.[2] This graph is much more attractive to look at, and it offers some improvements on the Scotese temperature portion, mostly because it's taking a more recent version of Scotese's schematic, but it still suffers from the out-dated ice-house vs hot-house model. The scale has changed. Instead of showing a 10-25 C scale, it shows the temperature range to be 10 C, while it should be 15 C. But what amazes me about this graph is that it goes back into Precambrian times. For temperature, that's okay; Scotese's schematic does that too. But the GEOCARBIII model this graph uses does not. It's strictly limited to the Phanerozoic. So whoever made this graph just stretched out the CO2 data so that it no longer represents the published GEOCARBIII model. And of course it still doesn't account for solar evolution. This appears to be another deliberate attempt to obscure the correlation between CO2 and temperatures, even to the point of fudging the CO2 graph. And we're still not done.

Example 4

This graph was tweeted by Moore,[3] and it appears to be an attempt to remove the Precambrian portion of the graph. I'm not sure if this was an attempt to fix the problem with Example 3. If it was, it didn't work. Rather than replotting the CO2 portion, the author of this graph just cut off the Precambrian and began with the Cambrian. Then we're treated to an arrow that is designed to generate alarm about the decrease in CO2 over geologic history.
Above, the top graph is to my knowledge the most recent version of Scotese's temperature graph. The graph shows two periods that were colder than the Quaternary. It also shows significant warming, and rapid by geologic standards, especially 250 million years ago at the end-Permian extinction. The eruption of the Siberian Traps during that time is likely responsible for the spike in temperature. But what's interesting is that contrarians generally don't use this graph. They also don't use proxy evidence for CO2 adjusted for solar evolution like the graph on the bottom. If they did that the correlation between CO2 and temperature would be too clear. See my previous post showing how this correlation is supported in the peer reviewed literature.

Conclusion and Reflection

Now you may be wondering, why are all these examples from contrarians so bad?[4] All of them display clear evidence of incompetence. All of them appear to contain deliberate attempts to obscure the correlation between CO2 and temperatures. All of them use outdated schematics for temperature and an old model for CO2. None of them account for solar evolution, and none of them show extent of glaciation, which correlates well with CO2 proxies and models. And there is no reason why the authors of these graphs couldn't have done the research in the scientific literature like I did to get the most up-to-date geologic evidence. And the people that use these graphs want to be called "skeptics." Really? Skepticism requires critical thinking and taking the time to check up on sources before promoting graphs found on the internet.

The reality is that a careful examination of geologic evidence undermines all four of the claims I cited above: 1) the geologic evidence shows that CO2 does correlate with temperature (see here), 2) climate changes are normal, but current warming is unusual and is disrupting the relative stability humanity has enjoyed throughout the Holocene (see here), 3) while most of the earth's history has likely been warmer than today, it's a non sequitur to say that current waring is good, and 4) CO2 levels have been declining, but CO2 levels have never become low enough to cause an extinction of plantlife, and CO2 levels are currently rising at rates never before detected in geologic history. I plan to have future posts addressing these more explicitly, but one thing is clear. Geologic history supports what climate scientists are saying about what humanity is doing with our CO2 emissions.

Comments

  1. Phil ClarkeNovember 29, 2022 at 10:23 AM

    You might like this. https://thetyee.ca/Analysis/2021/06/04/Fact-Checking-Patrick-Moore-Climate-Skeptic/

    ReplyDelete

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