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Atmospheric CO2 concentrations: AD 800-2000

19 Jun 2024 | Science Notes

From the CO2Science archive: What was done The authors developed a well-dated high-resolution history of the atmosphere’s CO2 concentration spanning the period AD 800-2000, based on measurements of stomatal density made on Tsuga heterophylla needles recovered from a sediment core that was extracted from Jay Bath (a shallow pond on Mt. Rainier, Washington, USA), after which they compared the new CO2 history with “selected temperature records.”

Paper reviewed: Kouwenberg, L., Wagner, R., Kurschner, W. and Visscher, H. 2005. Atmospheric CO2 fluctuations during the last millennium reconstructed by stomatal frequency analysis of Tsuga heterophylla needles. Geology 33: 33-36.

What was learned
The three-point moving average used by Kouwenberg et al. to emphasize centennial-scale CO2 trends reveals three major peaks: one centered on approximately AD 1000, one centered in the early 1300s, and one at the end of the record in the latter half of the 20th century. Interestingly, these are also the approximate locations of the three main peaks in the global temperature reconstruction of Mann and Jones (2003).

What it means
The authors say their results “corroborate the notion of a continuous coupling of the preindustrial atmospheric CO2 regime and climate,” which posits that the air’s CO2 concentration and temperature rose and fell close to simultaneously over this period. This conclusion, however, may be challenged by the very same data that were used to obtain it; for whereas the primary trend of the Mann and Jones temperature data over the first 1,100 years of their 1,200-year record was decidedly downward, the concomitant primary trend of the new CO2 data was upward. Clearly, more data will be required to resolve this major dichotomy.

3 comments on “Atmospheric CO2 concentrations: AD 800-2000”

  1. In the record of the last several million years, covering several Milanković cycles atmospheric CO2 concentration generally lags temperature changes by about 800 years, which is about the length of time it takes the oceans to "turn over." In the 500 million year record since life emerged on the Earth, temperature and atmospheric CO2 concentration are completely and chaotically unrelated. Details in my book "Where Will We Get Our Energy?" Everything quantified. No vague handwaving. 350 bibliographic citations so you can check I didn't just make up stuff.

  2. I draw your attention to a period that is rarely ever talked about - in fact, never talked about: the period from 1750 to 1850, and how that period flows through into 1850 to 1950. The data all comes from two organizations which have impeccable climate-alarmist credentials: Berkeley Earth Group and the Department of Energy. When you bring the two data sets together, they cancel any claim of human-driven climate change.

    If you look at the Berkely Earth temperature reconstruction from 1750 to 1850 (https://berkeleyearth.org/temperature-region/global-land), you find that in those 100 years, temperatures have risen roughly by 0.05 degrees centigrade. In the following 100 years, to 1950, temperatures have again risen by roughly 0.05 C. (Please note the incredible hike of nearly 0.08 C from 1750 to 1775: that is equivalent to the increase recorded from 1950 to today, but inside 25 years!)

    Now look at the DOE data (Tom Boden, Gregg Marland & Bob Andres: the site was closed in the 2010s) that reconstructs CO2 emissions from 1750 to today. From 1750 to 1850, when the industrial revolution was barely starting out, humans produced a paltry 1.3 gigatons of CO2 - and temperatures have shown massive variability, but finally registered roughly a 0.05 C increase. Then, from 1850 to 1950, when the industrial revolution really started to kick in, humans produced 63 times more CO2 than in the previous century - yet, temperatures have risen once again by only 0.05 C !

    From the observations I present to you here, one thing stands out very clearly: there is a total disconnect between human production of CO2 and increases in temperature. A production of CO2 63 times superior from 1850 to 1950 to that produced from 1750 to 1850 has not caused the slightest acceleration in the rise of temperature. In both centuries, the increase was of 0.05 C.

    There is a slight acceleration in temperature increase of about 0.07 C from 1950 to today, bringing the total rise in temperatures to 1.7 C since 1750 (that is already well above the totally irrelevant 1.5 C limit of the Paris Agreement). But I draw you attention to another discrepancy: from 1998 (apparently the hottest year of the 20th century) to today, humans have produced more than 50% of all the CO2 they produced from 1750 to 1998, for a total of about 196 gigatons, yet in that period, temperatures have risen only by about 0.04 C. Also, from 1950 to 2013, humans threw in the atmosphere 84% of all CO2 produced from 1750 to 2013, but temperatures since 1950 are up only 0.07 C, or half of the total temperature rise since 1750.

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