The first modern theoretical estimates by ECS were published in 1979 in the so-called "Charney Report" (Charney et al., 1979). They reported on page 2 about a theoretical ECS of 1.5 ° C to 4.5 ° C per doubling of the atmospheric CO2 concentration. This estimate included an estimate of the water vapor feedback, the impact of ice, and their assumed uncertainties. Without water vapor feedback, their calculated value was 1 ° C per doubling of CO2. They also give a likely value of 2.4 ° C on page 9, although they give a value of “close to 3.0” on page 2. The value on page 9 is not far from the empirical estimate of 2 ° C by Guy Callendar in 1938, but is well above the stated value of 1.2 ° C to 1.95 ° C (range 17% to 83% , best estimate 1.5 ° C) by Nic Lewis and Judith Curry (Lewis & Curry, 2018).
The IPCC estimates in its AR5 report (Bindoff & Stott, 2013) that the ECS is between 1.5 ° C and 4.5 ° C and does not provide a best estimate. This area corresponds exactly to the Charney report drawn up 34 years earlier. While the empirical, observation-based estimates have decreased significantly, the theoretical range has not changed, despite the fact that thousands of government-funded scientists have spent billions of dollars on it. The data is very similar today and it doesn't seem to matter to process it with more powerful computers and billions of dollars faster. It works the same way with manure.
Dive deep into the AR5 internals as Monckton et al. In MSLB15, an article titled "Why Models Run Hot: Results of an Irreducibly Simple Climate Model" (Monckton, Soon, Legates & Briggs, 2015), we see that the elements of the theoretical AR5 calculations suggest that the range is equal is narrowing down. Given the political environment at the IPCC, it is easy to assume that politicians are unwilling to admit that the theoretical risks of CO2-induced climate change are diminishing. As more empirical estimates of the CO2 effect emerge and more theoretical work is done, one wonders how long politicians can support the well-inflated 1.5 ° C to 4.5 ° C range.
ECS's estimates have long been in decline, as Nicola Scafetta and colleagues demonstrated in 2017. Figure 1 comes from their paper:
The decline in ECS estimates from 2000 to 2015. Source: Scafetta, Mirandola and Bianchini, 2017.
In the 1980s, the idea of a man-made (or anthropogenic) global warming disaster (CAGW) was developed. Since then, the alarmists have been beating the drum year after year. In the United States, a Senate committee meeting was held in the Dirksen Senate office building in Washington, DC on June 23, 1988, hosted by Senator Tim Wirth through CAGW. It was a hot and humid day in swampy Washington, DC. The meeting was a turning point, not least thanks to Dr. James Hansen from NASA. In his presentation to the Congress Committee, he said:
"1988 is warmer than ever in the history of instrument measurements."
“Overall, the evidence that the earth is warming by an amount too great to be a random fluctuation and the similarity of warming to that expected from the greenhouse effect is a very strong case. In my opinion … the greenhouse effect has been detected and is now changing our climate. "
“The currently observed global warming is close to 0.4 ° C, based on the“ climatology ”, which is defined as the mean value for 30 years (1951 – 1980). … We can state with 99 percent confidence that current temperatures represent a true warming trend rather than a random fluctuation over a 30 year period. "(Hansen, 1988)
ExxonMobil believed the natural variability was ± 0.5 ° C. They thought that a change had to be bigger to be significant. Obviously, Hansen somehow narrowed this natural area. The world cooled globally from 1944 to 1977 and began to warm in 1978. A rise of 0.4 ° C is not much. If you find that the "greenhouse effect" has been detected after a long period of cooling, your eyebrows should be raised. Notice that Hansen says "greenhouse effect" when he means "man-made greenhouse effect" or "enhanced greenhouse effect". There is a natural greenhouse effect caused by natural CO2 and other greenhouse gases, especially water vapor. This is the beginning of a misleading tactic often used by alarmists. In order to ignore the natural causes of climate change, they equate the “greenhouse effect” with the “man-made greenhouse effect”. They also use "global warming" as a synonym for "man-made global warming" and "climate change" is synonymous with "man-made climate change". This type of deceptive and manipulative language is still used today.
The IPCC reports
The first IPCC report (FAR), chaired by Bert Bolin, found that until 1992, when the report was published, global warming fell within the range of "natural climate variability" and was not necessarily due to human activity (IPCC, 1990 , P. 1) XII). They thought that definite identification of human influence was "unlikely for a decade or more". Bert Bolin believed James Hansen's 1988 congressional statement exaggerated the importance of recent global warming.
The second report, SAR, published in 1996 found that "the balanced evidence points to a discernible human impact on global climate" (IPCC, 1996, p. 4). However, this was based on unpublished and unverified work by Benjamin Santer and colleagues. His study suggested that climate model predictions of warming in the troposphere and cooling in the stratosphere were similar to what was going on. He called this a "fingerprint" of human impact on the climate (Santer et al., 1996a). After the paper was published, it was found that Santer had chosen his fingerprint (Michaels & Knappenberger, 1996). The study was dismissed and the IPCC humiliated. This humiliation was exacerbated by the fact that the politicians in charge of the IPCC were caught adapting the scientific reports within the SAR to their policy summary for policy makers (Seitz, 1996).
The third report, TAR, released in 2001, found that "most of the warming observed over the past 50 years is likely due to increases in greenhouse gas concentrations". (IPCC, 2001, p. 10). They based this decision on the "hockey stick" which later turned out to be flawed. At the time the fourth report (AR4) was published in 2007, numerous studies of the hockey stick showed that it was wrong and had too little variability. This was recognized in the fourth report AR4 by Keith Briffa, who wrote somewhat euphemistically that the hockey stick was too sensitive for certain proxies (tree rings) and the statistical methods (main components) with which it was created (IPCC, 2007b) p. 436 ). Willie Soon and Sallie Baliunas showed that the hockey stick did not reflect the data it was built with (Soon & Baliunas, 2003). The hockey stick turned out to be an elaborate fiction made up entirely of a flawed statistical process and a poorly selected set of temperature proxies (National Research Council, 2006, pp. 112-116) and (Wegman, Scott & Said, 2010, p. 112) 4-5, 48-50).
By the time AR4 was released in 2007, the leadership of the IPCC had given up on finding direct evidence that humans dominate climate change. They tried Santer's "fingerprint" and Michael Mann's "hockey stick" and couldn't convince the public either. In AR4, they tried to use climate models to convince the public that “most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations”. (IPCC, 2007b, p. 10). They do not present any observation results, only model results. The fifth report, AR5, was just a replica of AR4. Same two models, same result. As mentioned earlier, MSLB15 (Monckton, Soon, Legates, & Briggs, 2015) showed, deep within the AR5 internals, that the more recent AR5 model results suggest IPCC headlines overestimate climate sensitivity to CO2, but that finding became not explained or confirmed in the report.
While empirical calculations of the climate sensitivity to CO2 now show that the ECS is between 1.1 ° C and 2.45 ° C (see Table 1), the theoretical estimates remained 1.5 to 4.5, with the exception of AR4, as it was changed to 2.0-4.5. The ranges in Table 1 are all ranges from 5% to 95% as far as I can tell.
Table 1. Various estimates by ECS. All are theoretical calculations except for Lewis and Curry, whose estimate is based on observation.
Thousands of scientists and billions of dollars later, we still have the same theoretical uncertainty about the effects of CO2 on the climate. The one empirical estimate of the ECS shown is around 1.5 ° C. Most of these empirical estimates are below 2 ° C and are between 1.5 ° C and 1.6 ° C (Lewis & Curry, 2018). Guy Callendar's empirical estimate was 2 ° C (Callendar, 1938) and Arrhenius' theoretical estimate (Arrhenius, 1908) was 4 ° C. So it can be said that all the work and money that has been expended since 1938 has gone to attributing climate change to humans were wasted.
Is it getting better? What about the latest generation of theoretical models, CMIP6? Early signs suggest results are getting worse, not better, as reported by Ron Clutz and John Christy. While most of the new models have absurdly inflated ECS, it is interesting that the latest version of the Russian INM-CM4 model referred to in my previous post now predicts an ECS of 1.83. With the exception of INM-CM4, we haven't seen any progress since 1938. As my late grandmother Marie McCartney would say, "Now this ain't just dandy."
This is a condensed excerpt with minor changes from my new book "Politics and Climate Change: A History".
Click here to download the bibliography.