The fact is, there has been global warming, in which CO2 has played a modest but significant role. However, the contribution of human-generated carbon dioxide (CO2), or carbon dioxide of any kind, to further warming is diminishing with increasing rapidity and must eventually cease.

Global warming, technically Radiative Forcing (RF), occurs when greenhouse gases like CO2 absorb the earth’s infrared radiation and convert it to heat before it can escape into outer space. CO2 only absorbs infrared in two narrow frequency ranges, and there is only so much earthly radiation in those ranges. As CO2 increases in the atmosphere, it absorbs ever greater percentages of that radiation. When it is used up (reaches “saturation”), RF from CO2 must necessarily cease. CO2 has already fully absorbed the most easily absorbed frequencies and as it uses up the rest further heating from it becomes increasingly difficult, the additions to RF therefore slow, and full  saturation draws ever closer. So, there is a natural limit to how much CO2 can contribute to temperature, and to how quickly.

The charts below will be useful references for the reader.

Earth's energy budget

 

Earth's Global Energy Budget   Trenberth, Fasullo & Kiehl American Meteorological Society https://journals.ametsoc.org/view/journals/bams/90/3/2008bams2634_1.xml?tab_body=pdf

Ternberth et al. spent a decade developing and then refining this "energy budget" as better satellite and other data became available. It is widely cited in climate literature. Of the 396 W/sq. meter infrared radiation emitted by the earth's surface, all but 63 is already absorbed in the atmosphere and re-emitted toward the earth as global warming. The "atmospheric window," a range of frequencies in which greenhouse gases have little effect and in which CO2 has virtually none, accounts by their measure for 22 watts/sq. meter. Of the remainder, almost none remains in the frequencies affected by CO2.

Fig. 1

Radiance and Absorption

Fig. 2

This chart, originally prepared by physicist R. A. Rhode, sets out in graphical form the results of an elaborate calculation of infrared absorbance. The percentages of absorbency (the grey areas) in the lower set of graphs need to be read in conjunction with the curved lines in the upper graph, which show how much infrared radiation is emitted by sun and earth before atmospheric absorbance takes place. (The colored areas show how much gets through the atmosphere.) The lower set shows how much of that emission is absorbed. In the two top charts, the higher the curved lines are, the greater the radiance and the greater the energy.  (Be aware that that the vertical scales of sun and earth radiation are vastly different from one another.) The lower the curved line, the less radiance and energy. Thus, for example, the CO2 absorbance band around 14.5 microns is obviously significant, while the smaller CO2 band around 4.3 microns is not because there is very little earth radiance in that range for it to catch. (In addition, most if not all radiation in that range is already absorbed.) The earth emissions graph at the top has several curves in order to show what happens to the theoretical maximum for earth emissions at different temperature levels - as average temperature rises, the curve shifts to the left. The middle, dark blue curve approximates current average earth temperature. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174548

The Relationship between Atmospheric Carbon Dioxide Concentration and Global Temperature for the Last 425 Million Years W. Jackson Davis - MDPI

 

1st Essay of 3: Is Global Warming Real or a Hoax? Yes.

Carbon dioxide, as greenhouse gases go, is actually comparatively weak. Water vapor, by far the predominant greenhouse gas, is massively more effective in absorbing infrared radiation (which we experience as warmth) than CO2 (1), and massively more abundant in the troposphere(2), which is the region near the earth’s surface where climate takes place and life exists. Other greenhouse gases - methane, ozone, and the like, are  stronger absorbers of infrared than CO2 but are present in such small amounts that they are of minor significance(3). 

The only reason CO2 matters much at all is that its absorptive powers are largely concentrated in a very narrow but important range of about 13.5 to 16.4 microns in the infrared spectrum. It is in a part of that spectrum where most of the earth’s infrared radiation falls, between 7 and 50 microns. At 13.5 to 16.4 microns, it so happens, the earth’s infrared radiation level is quite high relative to other parts of the spectrum and water vapor’s absorptive powers relatively low. That leaves CO2 as the primary absorber in its narrow but important range (4). 

Please note the graph labelled Radiance and Absorption. Reflecting what is depicted, recent calculations indicate CO2 presently accounts for about 19% (6) of the 33 degrees Celsius, or 91 degrees Fahrenheit, global warming (technically known as Radiative Forcing or RF) that prevents the earth from freezing over entirely. That has been a good thing.

However, as can be seen, that narrow band is now nearing saturation at present concentrations of CO2, meaning most of the earth’s radiation in that range is being absorbed, mostly by CO2 and to some extent by what water vapor does absorb in this range. There is little left for additional increases in atmospheric CO2 to absorb (7). The observed logarithmic relationship between actual CO2 levels and actual RF reflect these facts, as well as other factors, including downwelling radiation from the stratosphere. 

(Incidentally, methane, also frequently mentioned as a greenhouse gas, is even more constrained by these considerations than CO2. Moreover, its even more limited absorption range is in an infrared region in which the earth’s radiation is very low. As can be realized from examining the Rhode chart above, it is a minor factor.)

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.(8) That means each additional X increase of CO2 contributes a successively smaller amount - about half - of additional RF than the one before. 

The logarithmic curve can be calculated mathematically.(9) It is widely accepted that the best approximation to actual temperature changes since the period 1870-1900 is  expressed as RF = ln5.35CO2, where RF is change in Radiative Forcing, hence temperature, expressed in degrees Celsius; ln means natural logarithm; and CO2 represents CO2 in the atmosphere expressed in parts per million (ppm).(10) The data to develop this curve were acquired empirically.

Observed RF in the industrial era till now therefore closely follows the theoretical curve (and also reflects methane, downwelling of radiation from warming in the stratosphere and above, feedback effects and any other factors at work, known or unknown) (See citations 1-5 in the text above). Average of the annual increases in CO2 concentration in the period 2010-2020 is about 2.44 ppm (2021 and 2022 were lower, but possibly for COVID related reasons)(11) To repeat the estimated (by IPCC) increase in that period of 1.1C at that decadal rate would take about 115 years. At that rate of increase in CO2, by 2100 mean global temperature would only increase about 0.6C, to about 1.9C in toto since the base period. Beyond that, the rate of increase continues to dwindle toward the  infinitesimal at any rate of increase.

More practically, in the period ahead, through 2050, this logarithmic relationship would produce an increase in RF of perhaps 0.25C to 0.30C.

It happens that the maximum additional global warming the IPCC currently considers acceptable is preferably 1.5 degrees but in any case less than 2.0 degrees Celsius from an average of the period 1870-1900, and reckons about 1.1 degrees have already occurred, using average results over several years, which is about 0.4 degrees short of the preferred 1.5 degrees.(12) So, if the world takes absolutely no steps to reduce CO2 emissions and their calculable rise, global warming from that base period would likely add perhaps 1.45-1.40C degrees from that 1870-1900 base period by 2050 and somewhere around 1.8C by 2100. If the world adopts the extremely costly and draconian measures the IPCC and others are urging in order to “save the planet,” then global warming, anthropogenic or otherwise, will add something similar or perhaps slightly less according to IPCC, but the draconian measures could then be credited with “saving” the planet. Not being privy to the deliberations of those doing the urging, I will leave it to the reader to consider whether their choice is coincidence.

In recent decades CO2 levels have increased at a faster rate than previously, probably reflecting accelerated construction of fossil-fuel  power plants in China, India, and numerous developing countries. That building trend seems likely to continue, perhaps even accelerate. If so, average temperatures may increase faster than indicated, and the levels at which additional warming from CO2 becomes negligible will then be reached sooner rather than later. “Negligible” is to some extent a subjective concept; to this author it appears to be in the region of 2.7-2.8C above the IPCC base.

The truth is, there is much more to global warming than human-caused emissions, CO2 included. Since the start of the industrial revolution, carbon dioxide is widely estimated to have risen from 280 ppm to the current 420 ppm-plus. That looks like a lot, and was added over a mere 170 years or so. But before that we had global warming for more than 10,000 years, at least since the end of the last Ice Age (albeit with some fluctuations), and there is evidence temperatures were actually somewhat warmer 9,000 years ago and again 4,500 to 8,000 years ago than they are today(13). Whatever the primary cause of that warming, it was not CO2. Atmospheric CO2  during those 10,000 years (and in previous ice-age cycles) was in the range of about 180 to 280 ppm,(14) much of the time below the preindustrial level of 280 ppm, though the gradual increase in CO2 during that period certainly contributed. Nor was it human activity. It was not all those power plants and factories and SUVs being operated by Stone Age cavemen while chipping arrowheads out of bits of flint. Whatever the cause was, it melted the mile-thick glaciers that in North America once extended south to Long Island and parts of New York City (15) into virtually complete disappearance (except for a few mountain remnants). That's one big greenhouse effect! If we are still having global warming - and I suppose we could presume we are, given this more than 10,000 year history - it seems highly likely that whatever it is, it would still be the overwhelmingly primary cause of continued warming. Perhaps we should be finding out what that cause (or set of causes) is, rather than worrying about CO2. 

One likely important contributor to long-term changes, both in the current Holocene and preceding Pleistocene periods, as well as long before, is the so-called Milankovitch Cycles, recurring perturbations in and other effects of the earth's orbit and orientation caused by the combined gravitational effects of the other planets in the solar system, the earth's moon, and the sun. They are thought to explain the long-noted phenomenon of strikingly regular recurrences of ice ages and interglacial periods. A good description of the phenomenon can be found here: https://www.space.com/milankovitch-cycles

 Consider the last eight grand Milankovitch cycles and the early strong upsurge in the current ninth, in which we are currently at or near previous peaks. Readings from the Vostok ice cores near the South Pole dating back 420,000 years (widely regarded as definitive) agree extremely closely with seabed sediment readings, indicating they were and are a worldwide phenomenon.  Insolation at high northern latitudes correlates with both but not perfectly, indicating other factors are involved. 

Yet even that trend-continuation today needs to be proved. Evidence is that the Medieval Warm Period centered on the 1200s was somewhat warmer than we are now(16), and climate was colder in the Little Ice Age culminating in the 1600s than it is now(17). (Whether the earlier Roman Warm Period around the time of Christ was as warm or was actually warmer than present is less clear.) So we are within the geologically recent range of normal up-and-down fluctuations without human greenhouse contributions that could be significant, or even measurable.

The idea that we should be spending trillions of dollars and hamstringing the economy of the entire world to reduce carbon dioxide emissions is beyond ludicrous in light of the facts above; it is insane. Furthermore, it sucks attention and resources from seeking the other sources of warming and from coping with - or taking advantage of - climate change and its effects in realistic ways. 

The true motivation underlying the global warming movement is almost certainly ideological and political in nature, with a growing helping of greed now that many billions of dollars are being steered toward “controlling” global warming, and I predict that Anthropogenic Global  Warming, as currently presented, will go down in history as the greatest fraud of all time. It makes Ponzi and Bernie Madoff look like pikers by comparison.

Many principal advocates, including many whose job description is “scientist,” arguing for fighting human-caused global warming have been demonstrably disingenuous[(18) and now you can see why. Those who knowingly have done this have proved they should not be trusted. 

CITATIONS

(1)  Absorption coefficient of carbon dioxide across atmospheric troposphere layer https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174548/ See especially Figure 1, reproduced above, which sets out graphically the comparative infrared absorption of relevant greenhouse gases.

(2) Fundamentals of Physical Geography, 2nd Edition 

by Micheal Pidwirney Concentration varies slightly with the growing season in the northern hemisphere.  HYPERLINK http://www.physicalgeography.net/fundamentals/7a.html Water vapor varies from 0% in places like the Altacama desert in Chile to as much as 4% in equatorial ocean regions, and should easily average at least 1% worldwide.  In that case, it would be 25 times more abundant than CO2. If (as seems reasonable) the global average is more like 2%, it would be 50 times more abundant.

(3) Ibid.

(4) Absorption coefficient of carbon dioxide across atmospheric troposphere layer https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174548/

(5) Absorption coefficient of carbon dioxide across atmospheric troposphere layer  Peng-Sheng Wei,∗. et al. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6174548/  The authors work with satellite data (which necessarily incorporate absorption and other characteristics from the upper atmosphere as well as the troposphere) and other resources to calculate an estimate of  what is happening in the troposphere alone.

(6) Journal of geophysical Research: Attribution of the present-day total greenhouse effect Gavin A. Schmidt, et al. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010JD014287   See Table 1 and related text. The key figure for this discussion is the amount of absorption attributed to CO2 under all-sky conditions in the presence of other infrared absorbers, because those are the conditions that exist in reality.  The others exist as perhaps-useful benchmarks for research. See text for details. The CO2 absorption is often reported as 25%, but that does not take into account absorption by H2O in the same ranges. Radiation absorbed by H2O obviously is no longer available to absorption by CO2 (and vice versa), reducing the effective absorption level of CO2.

(7) For another calculation of infrared absorption in the troposphere,  Saturation of the Infrared Absorption  by carbon dioxide in the Atmosphere International Journal of. Modern Physics Dieter Schildknecht. https://arxiv.org/pdf/2004.00708.pdf See Tables 1 through 7 and related figures and text. In particular, Tables 4 and 6 suggest absorption by CO2 Is somewhere between 80% (if you assume earth’s average relative humidity near the surface is 0%, which of course it is not) and 90% (if you assume average relative humidity is 85%). Note especially Fig. 3, which depicts the dramatic effect of adding absorption by H2O to that of CO2.

(8)   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.

(9)https://www.desmos.com/calculator/w1g0o7umlq Also useful: https://www.rapidtables.com/calc/math/Log_Calculator.html  

(10) The methodology is nicely summarized by the American Chemical Society here: https://www.acs.org/climatescience/atmosphericwarming/radiativeforcing.html Also see original paper: Meyhre, et al 1998 at https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/98GL01908  Note Table 3

(11)Annual Mean Growth Rate for Mauna Loa (of CO2) https://gml.noaa.gov/ccgg/trends/gr.html. Also, Mauna Loa Observatory https://www.co2.earth/daily-co2

(12) IPCC 2017 report, Ch. 1. https://www.ipcc.ch/site/assets/uploads/sites/2/2019/02/SR15_Chapter1_Low_Res.pdf - See the executive summary, et al. For easy quick reference, see FAQ on p. 79: FAQ 1.1: Why are we Talking about 1.5°C?

(13) Encyclopedia Britannica - Holocene Environment and Biota, et al. https://www.britannica.com/science/Holocene-Epoch/Holocene-environment-and-biota for early holocene. See also History of Earth’s Climate, Ch. 7, Brett Hansen http://www.dandebat.dk/eng-klima7.htm The citation here is of the English translation, which contains minor grammatical errors that do not materially affect content. 

(14) https://courses.washington.edu/pcc588/readings/Sigman_Boyle-Glacial_CO2_Review-Na00.pdf

(15). The Narrows Flood – Post-Woodfordian Meltwater Breach of the Narrows Channel, NYC Charles Merguerian https://www.geo.sunysb.edu/lig/Conferences/abstracts-03/merguerian-03.pdf p. 2, et al.

(16) Britannica, same section as citation (11) https://www.britannica.com/science/Holocene-Epoch/Holocene-environment-and-biota. For historical period: Roman and Medieval Warm Periods also History of Earth’s Climate, Ch. 7, Brett Hansen http://www.dandebat.dk/eng-klima7.htm

(17) Encyclopedia Britannica

https://www.britannica.com/science/Little-Ice-Age

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

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