Tuesday, December 1, 2020
Home Left Column Physicist Dr. Lubos Motl: 'One-half of CO2 doubling achieved...& Detectable impacts...

Physicist Dr. Lubos Motl: ‘One-half of CO2 doubling achieved…& Detectable impacts on the climate are yet to be seen’

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One-half of CO2 doubling achieved

http://feedproxy.google.com/~r/LuboMotlsReferenceFrame/~3/j9RvNVuz-JA/one-half-of-co2-doubling-achieved.html

Detectable impacts on the climate are yet to be seenWhen the CO2 level in the atmosphere surpassed 400 ppm a short time ago, many alarmists would celebrate this symbolic achievement. Oh, the CO2 concentration is so high! It’s a signal from the heaven, a shot from the Aurora telling us to start another world revolution because our previous one, that of 1917, has already faded away and it wasn’t enough for us, anyway. The number is so round, and so on. Of course, nothing new happens when the CO2 level reaches 400 ppm – it’s just another number that only looks special because of an arbitrary decadic numeral system we happen to use today. The Earth has seen concentrations around 6,000 ppm as well and 4,000 ppm would be just fine for all life forms we know today. By far the closest worrisome CO2 concentration is 150 ppm in which most existing plant species stop growing (ice ages have only forced them to easily withstand 180 ppm or so).Another numerically special value of the concentration was achieved two years ago or so but unlike 400 ppm, it wasn’t hyped by anyone. The hypothetical effect of CO2 on the temperatures (well, almost certainly real effect theoretically; hypothetical from an empirical viewpoint because the effect is so incredibly weak) is often quantified – converted to numbers – when we talk about the “climate sensitivity”, i.e. the increase of the global mean temperature caused by a doubling of the CO2 concentration.The doubling defines more natural benchmark values of the concentration because it suggests that we should look at the behavior of the temperature assuming the exponential growth of CO2. That’s natural because the temperature increase is approximately (very accurately) proportional to the logarithm of the temperature increase. The global mean temperature as a function of the CO2 concentration is\[T(c) = 14.5^\circ {\rm C} + {\rm sensitivity} \times \frac{\ln (c/280\text{ ppm})}{\ln 2}\] The temperature 14.5 degrees Celsius is the holy “optimum” global mean temperature that the climate alarmists want to see forever because it was how things probably were in 1750 although no one can really reconstruct the temperature in 1750 with a sub-degree accuracy (and even today’s “global mean temperature” depends on so many technicalities that it’s fair to say that it isn’t defined at a sub-degree accuracy, either). The ratio of logarithms may also be written as the “base two logarithm” but I wanted to use basic functions only.The coefficient “sensitivity” is theoretically equal to 1.2 degrees Celsius if we ignore all the feedbacks. The total figure when feedbacks (especially those related to various forms of water in the atmosphere) are included is unknown and it may be higher or lower than 1.2 degrees Celsius. One of the unjustified assumptions of the climate change ideology is that the full figure has to be higher. The higher value of the climate sensitivity you defend, the greater influence over the climate alarmist paramilitary movement you achieve. If you believe that the value of the total climate sensitivity is below an offensive threshold, you are a heretic. The offensive threshold used to be 3 degrees Celsius but the alarmists were forced to lower the threshold of heresy to 1.5-2.0 degrees Celsius because those values are obviously consistent with all the known data (and probably still overestimates).The CO2 concentration was around 280 ppm sometime in 1750 as well as in all interglacials. It has grown to 400 ppm today and the growth will continue, reaching the doubled value 560 ppm sometime after 2080. That’s just a result of estimates and projections, no one really knows whether the growth of CO2 will accelerate or decelerate but the growth not too far from the increase in recent years sounds sensible.When “we” reach 560 ppm after 2080, the ratio of logarithms in the formula above will be equal to one. That generates a certain increase of the temperature given by the climate sensitivity. When do we reach one-half of the climate sensitivity? Well, the concentration at that moment isn’t the arithmetic average of 280 ppm and 560 ppm. Because of the logarithm in the formula, the “middle concentration” is the geometric average of 280 ppm and 560 ppm. In other words, the half-way concentration is\[c_{0.5} = \sqrt{2}\times 280 \text{ ppm}\sim 396\text{ ppm}\] and it was reached sometime in 2012 or 2013. Now, we may compare the world in 1780 when the CO2 concentrations started to microscopically deviate from the natural background with the world in 2014. Lots of things have changed but the climate doesn’t seem to be among the things that have changed and we would notice. It becomes increasingly hard to reconstruct the temperature in the distant past but it seems sensible to assume that the temperature growth rate due to CO2 was negligible before 1850 and since 1850, we could have measured the temperature sort of well and the total increase from 1850 was something like 0.7 °C. (Indeed, it’s the same number we would quote 15 years ago, and it’s so for a simple reason: there has indeed been no warming at least for 15 years.) Let’s assume that Nature didn’t matter much so the increase between 1780 and 2014 was 0.7 °C.Imagine that you get the opportunity to meet your great great… grandmother who lived in 1780. You want to update her, tell her about all the interesting things that have taken place between 1780 and 2014. There are lots of things to say, aren’t there? Aside from your family tree, wars, scientific discoveries, fashion etc., you may also mention the climate change. “Granny, the most important thing I want to tell you is that the climate has changed. More precisely, the global mean temperature has grown by something like 0.7 °C in those 230 years. It’s sort of horrific. Please tell all the men around you to stop the steam engines and everything that uses some coal or oil.”That alarmist-descendant didn’t have to ask her for that because the granny was a herbalist, a witch, and a Luddite, anyway.That’s what some of the real alarmists would tell their great great… grandmother during the short encounter. The old lady would still have time to prepare a herbal tea in order to cure their self-evidently sick brain. “Aren’t you feeling ill?” she would rightfully and kindly ask her great great… grandson. (Did you see the research showing that all Ashkenazi Jews are 30th cousins of each other? They’re said to have started from a population of 300 people 800 years ago.) I say “rightfully” because the great great… grandmother lives in a village where the temperature goes up and down by 10 °C every day and the maximum and minimum achieved each day changes by additional 10 °C within most intervals that are several weeks long, too. She knows the seasonal cycles rather well (she had no air-conditioning system and a lot of work was needed for the heating) and she’s heard about some folks who have visited Africa where the temperatures are much higher – and perhaps some visitors to Siberia or the polar regions where the temperature may be below –50 °C. None of her thermometers may measure the temperature with a sub-degree accuracy and she can’t feel sub-degree temperature changes by her skin, either. The granny gave the descendant a lecture about the optimum weather for the tomatoes in her garden but the guy from the future stopped her because he is only interested in the looming global cataclysm.Instead, her great great… grandson tells her that one of the most important things that would occur in the next 230 years is the increase of the average temperature including all places on the globe (mostly completely irrelevant places) by 0.7 °C. What a disappointment. She would rightfully be disappointed by the quality of her descendants. She used to expect at least a sophisticated male witch and what she got was a picky hysterical bitch, instead. “Our family is going to go to a lavatory,” she would complain to her husband, the alarmist’s great great… grandfather.Now, imagine that the alarmist meets his great great… grandson who lives in the year 2084. Regardless of the feedbacks, the temperature difference caused by the rising CO2 between 2014 and 2084 is the same as it is between 1780 and 2014. The alarmist would say: “I just met my great great… grandmother in 1780 but she refused to stop the steam engines by a suicide attack and gave me a herbal tea instead. So the CO2 would be rising all the time between 1780 and 2084. Are you still alive? You must be burning!”Needless to say, the alarmist’s descendant would inform his ancestor that he is doing fine because one of the intermediate members of the dynasty got a brain transplant in 2050 which cured him of the alarmist seizures. (He didn’t explain how the surgery could have fixed the genetic alarmist pre-disposition of the family.) Otherwise the difference between the temperatures in 2084 and 2014 (the part caused by CO2) is the same as the difference between the temperatures in 1780 and 2014 (the part caused by CO2). It is negligible. It doesn’t deserve to be mentioned among the top 500 important developments between 2014 and 2084.Because we know that the temperature increase from the “first half-doubling” was about 0.7 °C, we may estimate the the temperature increase up to 2084 will be the same and the climate sensitivity could be around 1.4 °C if all the warming was due to CO2. The latter assumption is probably unrealistic because a part of the warming, perhaps almost all of it, was due to other, mostly natural reasons. The actual sensitivity may be smaller than 1.4 °C. However, it may be larger than 1.4 °C, too – it is conceivable but less likely that we got a warming even though the natural contributions were working hard to cool the globe. They could have been beaten.There are many unknowns and only probabilistic claims may be made and even those are usually subtle. However, it’s still possible to rigorously prove some definite statements that are not of probabilistic nature. For example, the following statement follows from the assumption that the dependence is logarithmic and the warming between 1780 and 2014 was 0.7 °C:The temperature increase in 2014-2084 will be at most 1.4 °C – or most of the temperature changes between 1780 and 2084 are natural in origin.I could be more specific what I mean by “most” and which “temperature changes” are evaluated to decide whether “most of them” were of natural origin – there are many specific versions of this proposition that may be proven – but they share the general point and it is the following:Either you admit that the temperature changes caused by CO2 are negligibly small as the observations in 1780-2014 indicate; or you say that the period 1780-2014 only saw a negligible temperature trend because the CO2 effect was cancelled by natural factors. But if you say so, it follows that the natural factors are at least equally important to CO2 and they may decide about the future and beat CO2, too.You just can’t have it both ways! Observations show that the “global warming” is negligible and you can only argue that there “should have been much more” if you admit that there are other very strong factors unrelated to CO2 – but those will prevent you from predicting the future temperature change and even its sign.Alarmists, indefinitely trying to invent rhetorical tricks that would imply that a dangerous climate change is looming, find themselves in between a stone and a hard place. On one hand, they don’t want to admit that the climate sensitivity or the warming rate is negligible because they realize that such an admission would reveal that they are promoting an ant to a global problem. On the other hand, they can’t really claim that the underlying trend caused by CO2 is much faster because that would imply that their predictions have already failed, or they need to admit factors that are completely beyond their control.There is no way out. If your job is to sell a self-evident lie, you are in trouble. Different alarmists are leaning towards one side of the trade-off or another. Many of them are often changing the strategy. But almost all of them keep on denying the fundamental conflict between the observations and the very point of their ideology and let me phrase the conflict again, in slightly different words: The empirical data make it clear that there can’t be a predictable yet high global warming. Either the CO2-induced warming is predictable, in which case the negligible increase before 2014 must be a good estimate; or the CO2-induced warming is high in which case one needs other, equally large factors that were canceling it, and the future is unpredictable because of these factors!The climate hysteria has considerably weakened in the last 5 or so years. But it’s still around and most alarmists are working hard to obfuscate things, observations, arguments, and calculations that are obvious to the naked eye.

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