First, carbon dioxide.



CO2 levels have fluctuated considerably over the last 541 million years, and for the last 250 million years have almost always been at far higher levels than today's readings (and usually significantly higher before that).(4) Obviously this was all without human contribution. The estimates vary, but consistently show levels of 500-2,000 ppm have prevailed during most of that 250-million-year period.



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.(5) 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 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. (6) 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 Ice Age minimum), growth in the large majority of plants is significantly stunted - cut roughly in half.(7) At 150 ppm photosynthesis and growth in most varieties of plants all but ceases and the plants die or are unable to reproduce.(8) 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 400 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.













( (15) https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014JD022466 - et al.





( (16) 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.)



( (17) The calculation of this figure 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.



(18) https://www.aqua-calc.com/calculate/humidity - Calculations of atmospheric carrying capacity for water vapor are based partly on observations and partly on theory, and can be quite complex. Using this calculator greatly simplifies doing so. Setting "Precision" at 3 decimal places is quite sufficient for this purpose.



A 0.43 C. increase from 15 C. (the current estimated mean global temperature) caused by doubling CO2 content would increase potential water vapor content by 2.65%. CO2 can be shown (see footnote 17) to contribute at most 30% of present global warming. Ignoring the effect of lesser greenhouse gases such as methane and attributing all the other 70% of global warming to H2O alone would at most add 2.33 times the CO2 contributions. Increasing that by 2.65% would yield an increased ratio of 2.40 times. That would add another 1.03 C to the CO2 contribution, for a combined total of 1.51 C., raising projected global mean temperature to 16.51 C, or 61.72 F..



Tripling CO2 would produce a 0.8 C. increase, or 2.96%. The boost to the water vapor ratio would be to 2.40 times. Combined total: 1.73 C., bringing the world up to near the lower part of the range that encompassed most of the Phanerozoic Eon.



Keep in mind these are all maximizing assumptions; actual changes in temperature, should they ever occur, would certainly be less than these maximized figures. It is left to the reader to estimate results assuming a more typical 50-70% range of average relative humidity.



( (19) 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.



( (20) 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.

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 above today's approximately 400 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 no more than a degree and a half Celsius (and preferably less) 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 if ever 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.(3) It is neither "normal" for our planet nor, as will be seen below, particularly "right."So then, what is the "right" and/or "normal" average temperature for the Earth, and what is the "right" and/or "normal" level of CO2 in the atmosphere?Second, temperature.Broadly speaking, the geological record indicates Earth's mean temperatures during most of the past 541 million years has usually been well ABOVE current temperatures. Estimates run 2 to 7+ degrees Celsius, or roughly 3.6 to 12.6 degrees F., above current levels(9), generally at or well above the 2 degrees C. (3.6 degrees F) increase often said to threaten ecological disaster.(10) Such temperatures are typical of today's tropics and subtropics,(11) so the earth has normally been a largely tropical planet for most of those 500+ million years. Yet the fossil record shows this period, the Phanerozoic Eon, was the time in which complex life 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).(12) 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 been only about 0.5 - 1.0 degrees C., or about one or two degrees F., higher than today.(13) For most of the rest of those times, they were higher. They rose from those Jurassic levels for tens of millions of years, then resumed their downward trend, which has continued to the present time. 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.(14)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.Temperature 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 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 otherwise.It is well known to scientists that the correlation between CO2 levels and RF 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.(15) That means each additional increment of CO2 contributes a successively smaller amount of additional RF than the one before. 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 increase CO2 contribution to RF by about 11.6%; tripling, about 18.3%.(16) In terms of degrees, that would mean a very modest rise from CO2's current 0.43 degree C.(17) contribution, to only 0.48 degrees C. after doubling; or only 0.51 C. degrees after tripling. The contribution of CO2 to further warming is diminishing.Such increases would slightly increase the potential of the atmosphere to hold more water vapor, another greenhouse gas. Doubling CO2 would then potentially add, even assuming relative humidity everywhere were to reach and stay at 100%, which it certainly will not, not more than 1.5 degrees C. of further warmth.(18) That would enter the lower end of the range that seems most favorable to life, but still be below what has been typical of geological history. In practice, the increase would be less. 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 which is not now in evidence. "Runaway" warming to dangerous levels is not in prospect.Another question is widely raised: What about sea levels, which are rising 2-3.2 mm/year?(19) 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. 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.(20) 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, which 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.FOOTNOTES(1) 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) https://www.britannica.com/science/Phanerozoic-Eon(3) https://commons.wikimedia.org/wiki/File:Phanerozoic_Climate_Change.png It should be noted that due to greater uncertainty of measurements for the earlier, pre-Carboniferous eras, temperatures then may have been higher than shown here. (See Royer, et al. reference in text, which is also cited below)(4) http://www.geosociety.org/gsatoday/archive/14/3/pdf/i1052-5173-14-3-4.pdf See especially charts on pp. 5,6. This is the Royer, et al. citation mentioned above.(5) 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.(6) https://www.nasa.gov/feature/goddard/2016/carbon-dioxide-fertilization-greening-earth(7) https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-8137.2010.03441.x See especiallystarting on p. 681 and pages following. See also the citations referenced in this study's section 2.(8) See citation (7).(9) http://www.geosociety.org/gsatoday/archive/14/3/pdf/i1052-5173-14-3-4.pdf See especially Figure 4 and related material. (This is the previously cited Royer study, at a different ingernet location.)(10) https://www.livescience.com/41690-2-degrees-of-warming-too-much.html et al.(11) 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.(12) https://www.mdpi.com/2225-1154/5/4/76 - by W. Jackson Davis. See especially Figure 5 in, and related text. Click on the icon marked full text or the icon marked PDF fro 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.(13) As calculated in citation (12).(14) http://www.essc.psu.edu/essc_web/seminars/spring2006/jan18/Zachosetal.pdf - J. Zachos, et al (2001) -292 (5517), 686-693 Temperature ranges are somewhat greater in this study, but the general pattern is basically the same, as more roughly indicated in the Davis paper in citation 12.