Phanerozoic – Progressive Detail

CSS-15 The Phanerozoic covers close to 600 million years of history where life was abundant on the planet. That constitutes a lot of data. There are a few plots showing this data (with progressively more detail, the closer we get to the present). With the acquisition of Westerhold’s 2020 benthic foraminifera oxygen/carbon isotope data compilation, C.R. Scotese’s 2021 Phanerozoic Temperature Update and R.A. Berner’s 2005 GEOCARBSULF CO₂ Update, I was able to put together an updated version. The plot is interesting but is not a great place to draw any significant conclusions on Climate Change (on either side of the “discussion”). The Catastrophic Anthropogenic Global Warming (CAGW) alarmist crowd will point to some of the general trends where you can argue that the global temperature and CO₂ concentrations correlate (examples below).

1. The Paleocene–Eocene Thermal Maximum (PETM) event at roughly 56 million years ago.
2. The decline in both Global Temperature and CO₂ concentration off the Eocene Climate Optimum.
3. The tightly correlated Global Temperature and CO₂ concentration visible in the ice core data from the planet’s poles.
4. The sharp rise in CO₂ (140 ppm) and the IPCC’s 1.07 °C Temperature increase estimate from pre-industrial levels.

However, the devil is in the details and correlation is not evidence of causation.

#climatechange #delaythegreen #globalwarming #showusthedata

1. The PETM event was a short-term dramatic increase of both temperature and atmospheric CO₂ concentrations. The PETM is used as a means to link “global warming” and CO₂ emissions. Unfortunately, for the CAGW alarmist crowd, Wikipedia claims that the “cause, details and overall significance of the event remain uncertain”. Wikipedia does suggest that the North Atlantic Igneous Province (a major volcanic event) likely played a role in the increased CO₂ levels. However, that does not fit well with the CAGW alarmist computer programming mindset. When volcanic activity ramps up, there is an associated CO₂ release into the atmosphere (that would cause some minor warming). But there is also an aerosol release that has a more significant, more powerful cooling effect on the planet. There is also a resolution issue on these long-time scales. However, the temperature does appear to move first, followed by the CO₂. But you have to ask how much of the PETM temperature increase is due to CO₂ and how much is due to whatever triggered the PETM. CO₂’s Climate Sensitivity is around 1 °C, which means the CO₂ rise or fall (between the 1300 ppm base and 2900 ppm peak) would only account for just over 1 °C of the PETM 5-8 °C temperature change. Remember as temperatures rise or fall, CO₂ concentrations also rise or fall in tandem. You can potentially explain some of the increase in CO₂ with the volcanic activity, but the immediate drop back to background levels suggests that the more simple, traditional Temperature Driving, CO₂ Responding relationship is still the dominant mechanism.
2. The temperature and CO₂ decline off the Eocene Climate Optimum can generally be correlated. But as with the PETM, you must ask how much of the temperature decline can be contributed to CO₂ and how much is due to other natural forcings (increasing Cosmic Ray Flux and the Tethys Sea Closure (from 47-34 Ma BP)). Again, CO₂’s Climate Sensitivity is around 1 °C, which means the CO₂ drop (from roughly 2000 ppm to 1200 ppm (just prior to the sudden temperature drop (due to the Chesapeake Bay and Popigai impacts) at the Eocene/Oligocene boundary) would only account for less than 1 °C of the 5 °C temperature drop over that period.
3. The very good correlation between CO₂ and Temperature, visible in the ice core data, was used by Al Gore in his debunked “Inconvenient Facts” movie to push the CAGW alarmist Narrative. Unfortunately for the CAGW alarmist community, a detailed look at the data over this period, shows that temperatures were moving first with CO₂ responding. Over the last million years, the temperature changes have been driven by the Milankovitch cycles. As temperatures rise, atmospheric CO₂ rises (with several century delays) as the oceans release CO₂. And as temperatures decline, CO₂ declines (with millennia delays) as CO₂ is reabsorbed by the oceans. I suspect a version of the Milankovitch cycles is active throughout the planet’s history, but the Milankovitch analysis is usually restricted to comparisons with the more recent ice core data. As with the two previous discussions, the CO₂ increase from 180 ppm (at the depths of the Last Glacial Maximum) to our current levels of 420 ppm would account for not much more than 1 °C of the roughly 7 °C temperature rise.
4. CO₂ concentration levels have increased significantly from the lows of pre-industrial levels (280 ppm, and the life-threatening lows of the LGM (180 ppm)), but those increases (to just 420 ppm) are not significant when compared to the planet’s historical Phanerozoic levels (2,000 to 7,000 ppm). Again, there is correlation between CO₂ and Temperatures over the Modern Temperature Record (MTR, 1850 to the present) and the CAGW alarmist crowd likes to claim that most (if not virtually all) of the temperature rise is due to CO₂. But a better correlation can be achieved using just Total Solar Irradiance (TSI as a proxy) and the Atlantic Multidecadal Oscillation (AMO). Refer to OPS-8 – A Basic Climate Model and my Open Letter Addendum for detail. So, which one is correct? Trick question, neither one. My model ultimately should include a small CO₂ component and/or should incorporate other ocean cycles to tighten the correlation. While the IPCC modeller’s simplistic, unscientific focus on one parameter (CO₂) ignores the natural forcings that are visibly active throughout the pre-MTR Holocene (when CO₂ was virtually flat), were still active during the MTR and will continue to be active in the real world’s future. A couple of key points should be noted. Firstly, half of the MTR temperature rise occurred pre-1950, but over 86% of human CO₂ emissions have occurred post-1950. CO₂ is obviously not the only radiative forcing active over the MTR. Even post-1950, CO₂ is not acting alone (and is often overpowered by ocean cycles and small changes in solar activity). Hmmmm…. Secondly, the “scary” MTR CO₂ rise is not scary when CO₂ and Temperature are plotted together on scales that reflect the CAGW alarmist narrative (i.e.: 1.07 °C = 140 ppm). Those concepts are discussed in my OPS-51 – Late Holocene – CAGW CO₂-Temperature and OPS-54 – CO₂-Temperature – Properly Scaled.

The previous discussions all assume that CO₂’s Climate Sensitivity is constant at around 1 °C. As shown in my CSS-7 – CO₂ – The FECKLESS GreenHouse Gas post, the CO₂ Climate Sensitivity declines as CO₂ concentrations increase. Ultimately, the data shows that CO₂ is a minor contributor to climate change. Additional back-up for these discussions is included in my CSS-10 – A Ride Through the Cenozoic and CSS-12 – Cosmic Ray Discussion posts.