2nd Essay of 3: Is Earth Too Warm and CO2 Too High - or Too Cold, and CO2 Too Low?

Climate discussions often seem to take for granted that the "right" amount of CO2 in the atmosphere is around the 280 parts per million (ppm) that prevailed at the start of the industrial revolution, or at least not much above today's approximately 425 ppm; and that something near or below today's average global temperature (which is about 15 degrees Celsius, or 59 degrees Fahrenheit) is the "right" temperature. It is asserted that only a degree and a half Celsius (or in any case less than two degrees) above that level is acceptable.(1) Earth's long-term geological history indicates these assumptions and that assertion are very much in error.  It would appear that quite different - and higher - levels that prevailed in the past would be more desirable today.

Recent readings are in fact at extraordinarily low levels only rarely experienced by the earth in the 541 million years of the Phanerozoic Eon, the time in which large, visible multicelled organisms have left fossils.(2) In terms of that extremely long geological record, we are living in a highly anomalous environment. It is neither "normal" for our planet, if normal is taken to mean typical,  nor, as will be seen, particularly "right."

For the discussions below, it will be helpful to refer to the useful chart in this blog labelled: The Relationship between Atmospheric Carbon Dioxide Concentration and Global Temperature for the last 425 Million Years W Jackson Davis. 2017 https://www.mdpi.com/2225-1154/5/4/76/htm (Please excuse my limited computer editing skills for not inserting it here.)

So, what is the "right" and/or "normal" average temperature for the Earth, and what is the "right" and/or "normal" level of CO2 win the atmosphere?

First, carbon dioxide.

Estimates vary but agree that CO2 levels have fluctuated considerably over the last 425 million years, and for the last 200 million years have also almost always been at far higher levels than today's readings. Obviously this was all without human contribution.

At lower CO2 concentrations such as today's and those of the geologically recent past, plant growth is less than optimal. That is why commercial greenhouse operators often add CO2 to encourage plant growth.(4) By trial and observation, they have found optima for plant growth range from 800 to 1,500 ppm depending on the plants being raised - two to three-plus times greater than present-day levels. If one's standard is what is good for life on earth, this would suggest that the "right" levels of CO2 are at least two to three times present levels. If the recent CO2 increases continue, they therefor should help the world's vegetation grow better, whether the increases are natural or manmade; there is measurable evidence this is actually happening even at current levels.(5)  That of course also means more food and therefore a better environment for animal - and human - life.

On the other hand, at 180 ppm growth  (the generally agreed Ice Age minimum), growth in the large majority of plants is significantly stunted - cut roughly in half.(6) At 150 ppm photosynthesis and growth in most varieties of plants all but ceases and the plants die or are unable to reproduce.(7) Animal life would soon starve. That preindustrial 280 ppm is far closer to the levels that extinguish life than to the much higher "greenhouse" levels that optimize it.

In summary: Maximized benefit for vegetation growth takes place at 800-1,500 ppm, not at today's 425 ppm or so. If the flourishing of life is your standard for what is "right," adding CO2 to the atmosphere is actually a good thing.

Second, temperature.

Broadly speaking, the geological record indicates Earth's mean temperatures during most of the Phanerozoic Eon has usually been well ABOVE current temperatures. For the more recent 200 million years of that eon, estimates in a widely cited study(8) range up to 4.5 degrees Celsius, or 8 degrees F., above current levels, generally at or well above the 2 degrees C. (3.6 degrees F) increase often said to threaten ecological disaster.(9) Such temperatures are typical of today's tropics and subtropics(10), so the earth has normally been a largely tropical planet for most of those 541 million years. Yet the fossil record shows this period, the Phanerozoic Eon, was the time in which complex life generally flourished and evolved into ever more diverse and complex forms and spread across all the earth.  Today, such regions include some of the most populous countries in the world - such as India and Indonesia, and southern China - and some of the most densely vegetated regions with the greatest diversity of speciation - the Amazon jungles of South America and the jungles of central Africa, as well as of southeast Asia. Life, including human life, clearly does very well at such temperatures.

The highest readings were in the first half of this 541-million-year eon, trending downward (with fluctuations).(11)  But consider the second half, during most of which temperatures also were substantially higher than at present, also with an irregular,  gradual downtrend. For one period of about about 40 million years during the Jurassic and Cretaceous periods, when dinosaurs roamed the earth, mean temperatures, by the more conservative calculations, may have fallen to as little as 0.5 - 1.0 degrees C., or about one or two degrees F., higher than today.(12) For most of the rest of those times, they were higher than that. Starting some 33 million years ago, average earth temperature fell below the previous Jurassic minimum for about 9 million years, partially recovered, then gradually fell again. Whatever the reasons, average temperatures took an additional lurch downward starting about 6-7 million years ago to the levels of the current Pleistocene Epoch, the regime of recurring Ice Ages and interglacial warming periods that has prevailed until today.(13)

These colder temperatures that have prevailed for the last 2.6 million years, bracketing the Ice Ages, are therefor a relative rarity both in all the last 541 million years and in the last 250 million. Temperatures have fluctuated during the Pleistocene (Ice Ages) Epoch also, in a range producing intervals of massive glaciation alternating with intervals of rapid meltdown, such as the present one that began some 10-12,000 years ago. But even our current interglacial meltdown temperatures are unusually cold for the earth when compared to the record of those last 250 million years. They are not "normal," given known geological history, for our planet during the time in which complex life forms have proliferated, except in the sense that they are continuing a long-term decline into record low levels. The accompanying glaciation, wherever and whenever it occurs, is obviously inimical to life.

What about the "right" temperature? That implies imposing a value judgment about temperature, which is a morally neutral natural phenomenon. If "right" temperature is taken to mean most conducive to the flourishing of life, which is the standard suggested here, it "should" also be significantly higher than today. If "right" means the continuation of the long-term decline, it would ultimately, some millions of years into the future, lead to calamitous glaciation endangering the existence of life, at least life in complex forms such as human beings. From the point of view of human beings and other existing complex organisms such continuation may reasonably be deemed undesirable.

Temperatures most consistent with abundantly flourishing life in both the past and the present would appear to approximate those of today's tropical and subtropical zones, suggesting average global temperatures of perhaps 17-22 degrees C. (63-72 degrees F.), compared to today's average of 15 degrees C. (59 degrees F).

Climate discussions also raise at least two other issues about the possible future based on erroneous beliefs.

Since CO2 is a greenhouse gas, as concentrations increase, they should add further to global warming, the technical name for which is Radiative Forcing (RF). But by how much? Could it be enough to create a hypothesized "runaway" warming that could extinguish or at least greatly harm life, or at least human life? The past geological record, in which much higher concentrations of CO2 than present produced no such thing, clearly indicates it would not.

There is a severe restraint, which is discussed in the previous essay. For convenience, that discussion is recapitulated here:

"It is well known to scientists that the correlation between CO2 levels and RF to date is not, as many appear to assume, a linear correlation, in which each X increase in CO2 would produce the same Y increase in RF. Instead, the relationship is logarithmic.(14) That means each additional X increase of CO2 contributes a successively smaller amount of additional RF than the one before. The logarithmic curve can be calculated mathematically.(15) Mathematically, doubling total CO2, not merely the human-generated portion, from current levels (which is not now in prospect in either human or even geological terms) would theoretically increase CO2 contribution to RF by about 11.4 %; tripling, about 19.5%. In terms of degrees, the doubling implies a 1.7 degree Celsius increase, tripling about 2.0.   (16). Observed RF till now closely follows the theoretical curve (and also reflects downwelling of radiation from warming in the stratosphere and above and any other factors at work). Average of the annual increases in CO2 concentration in the period 2020-2021 is about 2.32 ppm(17); a doubling at that rate would take about 184 years, a tripling about 368. Beyond that, the rate of increase continues to dwindle toward the infinitesimal.

More practically, in the period ahead, through 2050, this logarithmic relationship would produce an increase in RF of about 0.375 degrees Celsius."

That logarithmic curve means that further temperature increases peer unit of CO2, already slowing to a relative crawl in the immediate future, must dwindle toward the infinitesimal. If temperatures are to continue rising more than that, even to reach levels maintained for hundreds of millions of years in the geological past during which life flourished, some other, additional source of warming is needed. "Runaway" warming to dangerous levels is not in prospect, certainly not from increases in CO2.

Another question is widely raised: What about sea levels, which are rising 2-3.2 mm/year?(18)  Do not catastrophic levels loom as the earth's ice continues to melt? The answer is no, because the change is so gradual. Consider New York City, situated in a major natural ocean harbor. New York was founded about 400 years ago. It has changed greatly since then. In another 400 years from today, when it is likely to have changed greatly again, that rate of rise would raise sea level in NYC  2.4 to 4.2 ft., which would have virtually no effect on even existing structures, if they still then exist, just as the preceding 400 years have not.  In 1,000 years, that rise would be 6 - 10.5 feet; probably requiring sea walls, if people are still choosing to live in NYC in that remote (by human standards) time. In 5,000 years, roughly equal to all of recorded human history to date, at current rates the rise would add 30-52.5 ft., and NYC would probably have to be moved upstate, perhaps to adjacent Westchester County, whose airport is listed as 439 ft. above sea level.(19) Doubling the rate of rise would mean sea walls in a mere 200 years or so, and moving upstate would still be a millennium or more away. To get to that seawall level by the year 2100, as some predict, would require a ten- or twelve-fold acceleration, of which there is no sign whatsoever.

Conclusion: rising levels of CO2 and temperature within the ranges seen in the last half-billion years may substantially enhance life on earth, and in the distant (in human terms) future could eventually require substantial adaptation. That is something the human race has proved itself to be quite good at. Whether this prospect should be welcomed depends on how greatly you value the flourishing of life on earth. It should not be feared.

CITATIONS

(1) IPCC Report 2017 https://www.ipcc.ch/site/assets/uploads/sites/2/2019/02/SR15_Chapter1_Low_Res.pdf - IPCC 2017 report, Ch. 1. See the executive summary, et al.

(2) Encyclopedia Britannica https://www.britannica.com/science/Phanerozoic-Eon

(3) The Relationship between Atmospheric Carbon Dioxide Concentration and Global Temperature for the last 425 Million Years W Jackson Davis. 2017 https://www.mdpi.com/2225-1154/5/4/76/htm See especially Figure 5 in Section 3.2 - Temperature vs. Atmospheric carbon dioxide, and related text. (Click on the icon marked full text or the icon marked PDF for the full study.) The temperature curve in Fig. 5 of the full study has been smoothed for clarity, and so does not reflect periods shorter than several million years except very recently, during the Ice Ages, for which readings are much more numerous. Thus, for example, any violent temperature fluctuations associated with the asteroid strike that extinguished most dinosaurs 65 million years ago would have lasted only a few decades at most and are not reflected.

(4) http://www.omafra.gov.on.ca/english/crops/facts/00-077.htm This fact sheet prepared by Canada's Ontario Province dates back to 2002, but is still in use because it provides a good summary and explanation of desirable CO2 levels.

(4)https://extension.okstate.edu/fact-sheets/greenhouse-carbon-dioxide-supplementation.html

(5) https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fertilization-greening-earth

(6) Plant responses to low [C)2] of the past. Gerhart & Ward, 2010https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2010.03441.x  See especially section 2. Biomass production starting on p. 681 and pages following. See also the citations referenced in this study's section 2.

(7) Ibid.

(8) CO2 as a primary driver of Phanerozoic climate Dana L. Royer et al. http://www.geosociety.org/gsatoday/archive/14/3/pdf/i1052-5173-14-3-4.pdf See especially charts on pp. 5,6, and 8. Differences in sourcing and methodology may account for the difference in temperature estimates prior to 200 million years ago between this and the study cited in (3), but still show reasonably good agreement for the period since 200 million years ago. The general shape of the trend curves are similar in both periods despite the divergence. Note the interesting relationship between temperatures and cosmic rays in curve C. 

Also see a more recent study:Ocean Temperatures Through the Phanerozoic

Reassessed. Grossman & Joachimski https://www.nature.com/articles/s41598-022-11493-1.pdf

(9)https://www.livescience.com/41690-2-degrees-of-warming-too-much.html et al.

(10) http://www.weatherbase.com Cities (and their neighboring areas) with average yearly temperatures of 20 - 27 degrees Celsius are within the global range estimated for most of the Phanerozoic eon.

(11) see citation 3.

(12)  See citation (8).

(13) Trends, Rhythms, and Aberrations in Global Climate 65 Ma to present, J. Zachos, et al (2001). Science 292 (5517), 686-693 http://www.essc.psu.edu/essc_web/seminars/spring2006/jan18/Zachosetal.pdf See especially Fig. 2 on p. 688. Temperature ranges are estimated much greater in this study of the past 65 million years (since the dinosaurs went extinct) than the others cited, but the general pattern is basically the same, as indicated in the Davis paper in citation 3.

(14) Journal of Geophysical Research: Atmospheres Why logarithmic? A note on the dependence of radiative forcing on gas concentration Huang and Shahabadi https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JD022466 - et al. Not only CO2 RF is logarithmic.

(15) https://www.rapidtables.com/calc/math/Log_Calculator.html  Use this logarithmic calculator to find the logs of the starting and ending numbers, and divide the difference between them by the starting log. The result is the percentage amount of the ending figure (in decimal form) compared to the beginning figure. (For simplicity, calculate using the standard or "natural" log to the base 10.)

(16) The calculation of temperature increase was set out in the companion essay, "Is global warming real or a hoax? Yes." where it is supported by citations referenced in its footnotes 1-5, to which the reader is referred.

(17) Annual Mean Growth Rate for Mauna Loa (of CO2) https://gml.noaa.gov/ccgg/trends/gr.html

(18) https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-14/ - The lower figure is a projection from the approximate rise in sea levels from 1880 to present; the higher figure is a projection from the more rapid rise measured in the latest two decades. It should be noted there have been other periods within the 1880-present record when levels rose as fast or faster as in the latest two decades, as well as periods in which actual declines were recorded.

(19) https://airplanemanager.com/Airports/HPN

        Please feel free to copy this essay and post it wherever you think it will do some good. The more people have a chance to read and consider it, the better.