From Watts Up With That?

The Global Emissions Experiment: A 33-Year Audit

By Christopher Monckton of Brenchley

Almost a third of a century has passed since IPCC issued its First Assessment Report in 1990. How, then, have the excitable predictions of the profiteers of doom panned out during the 33-year experiment in ever-increasing emissions of CO₂ and other greenhouse gases? Here is a brief audit of that continuing experiment.

First, how much global warming did IPCC predict in 1990? Its predictions were grouped under four emissions scenarios A-D. The anthropogenic forcings from 1990-2020 predicted under emissions scenario B in Fig. 2.4B of IPCC (1990) are very nearly identical to the forcings in Fig. A.15,in which IPCC assumed that annual anthropogenic emissions in each year from 1991-2020 would be equal to emissions in the year 1990:

In reality, however, anthropogenic emissions rose from 1991-2020 in line with IPCC’s CO₂ prediction for the business-as-usual emissions Scenario A, which is, therefore, the scenario closest to outturn.

Emissions rose very sharply from 32.5 billion tonnes CO₂ equivalent in 1990 to almost 50 btCO2e in 2019, as the global-emissions graph from Our World in Data shows:

Accordingly, scenario A, the business-as-usual scenario, is what has transpired since 1990. The reason is that some 70% of new emissions are arising in Paris-exempt developing countries (such as China and India):

IPCC (1990) predicted about 1.9 W m^–2 anthropogenic forcing on Scenario A, but little more than 1 W m^–2 has occurred in the 33 years since the prediction was made.

Here is a facsimile IPCC’s Scenario A global warming prediction made in 1990. Note in particular that the emissions scenarios are just that – emissions scenarios. Note also that IPCC made a prediction and not a projection.

However, since the observed 1 W m^–2 forcing was little more than half the 1.9 W m^–2 predicted by IPCC (1990) for emissions under Scenario A, the 0.13 K decade^–1 warming rate since 1990 (UAH) was well below half the 0.3 K decade^–1 midrange decadal warming rate predicted under Scenario A.

To summarize: IPCC correctly predicted the business-as-usual emissions in Scenario A, but predicted almost twice as much consequent anthropogenic radiative forcing as has occurred since 1990, and more than twice as much decadal warming as has occurred since.

IPCC’s original Scenario A prediction provides a useful rule of thumb: predicted equilibrium doubled-CO₂ sensitivity ECS (the standard metric for climate-sensitivity studies) is ten times the predicted decadal warming rate: 3 K ECS against 0.3 K/decade. Let us call this rule of thumb the tenfold rule.

Given the factor-2 excesses of predicted forcing and predicted warming compared with outturn since 1990, a scientific (as opposed to merely political) body could, should and would have reduced its ECS prediction in line with observation. Following the tenfold rule, instead of predicting 0.3 [0.2, 0.5] K decade^–1 warming and consequently 3 [2, 5] K ECS, IPCC should now be predicting 0.13 K decade^–1 warming and consequently 1.3 K ECS.

As I showed in a recent posting, Monte Carlo distribution based on mainstream values for the five variables informing the energy-budget method, which depends far less on models than IPCC’s method, indeed indicates 1.3 K midrange ECS, cohering with observed warming.

The first question arising is how climate scientists could have been so wrong in their predictions of the forcing arising from the business-as-usual emissions that have occurred since 1990, and in their predictions of the consequent global warming.

The second question arising is why, faced with the plain evidence set out here to the effect that the original predictions were grossly exaggerated, IPCC persists to this day in following the tenfold rule as applied to its 1990 prediction, in that it continues to predict 3 [2, 5] K ECS, in line with its 0.3 [0.2, 0.5] K decade^–1 business-as-usual prediction in 1990 for medium-term warming in the following decades.

The third question arising is why, given the above proof of the disastrous and costly failure of climatology’s original predictions, the models on which IPCC relies continue to predict even larger warming even than IPCC. The CMIP6 models predict 3.9 K midrange ECS, exactly thrice the rate they should predict in accordance with the tenfold rule.

The direct warming that the models predict in response to doubled CO₂ is just 1.2-1.3 K, which is consistent with the observed 0.13 K/decade warming. However, the models multiply that direct warming, or reference sensitivity, by about 3 to allow for temperature feedback, chiefly from more water vapor in warmer air. But, as Professor Lindzen says in his recent interview with Jordan Peterson (watch it now before the climate Communists in control of YouTube censor it), the le Chatellier principle would lead us to expect that under anything like modern conditions feedbacks would be more or less self-canceling.

Any rational government, on conducting a similar audit, would conclude that the original fears of rapid and catastrophic global warming have proven entirely groundless, and that, given the plummeting annual death rate from weather-related events, the mild warming we may well continue to cause will continue to be as net-beneficial as it has been until now. There is certainly no conceivable justification, on the evidence that has accumulated since 1990, for any action whatsoever to mitigate future global warming. There will not be enough of it to do anything but good.

Mathematical footnote

It is interesting to derive the interval of absolute feedback strength Λ₂ implicit in the projected ECS ΔE₁ on 3 [2, 5] K; doubled-CO₂ forcing ΔQ₁ on 3.93 [3.46, 4.4] K; and Planck parameter P on 3.22 [3.4, 3.0] W m^–2 K^–1 (IPCC 2021).

Where (1) gives doubled-CO₂ feedback response ΔB₁, and where (2) gives the total feedback response B₂ following a doubled-CO₂-equivalent forcing compared with 1850 given the fraction H₂ of equilibrium temperature represented by B₂, (3) gives the absolute feedback strength Λ₂, here derived by Monte Carlo distribution from IPCC’s intervals of ΔE₁, ΔQ₁, P, starting with the 287.5 K global mean surface temperature in 1850 (HadCRUT4) and the 20 K total feedback response B₁ in that year.

One final question arising. Does anyone seriously imagine that a feedback-strength interval as narrow as just 0.05 W m^–2 K^–1 can be reliably diagnosed from the outputs of the general-circulation models? All attempts at deriving ECS by feedback analysis, including all attempts at diagnosing feedback strengths and consequently ECS from models’ outputs, are doomed to failure, since the underlying data are far too uncertain.

That is why the energy-budget method, which is not dependent upon feedback analysis, is prefereable. However, in paper after paper it shows a far lower ECS than the models do – indeed, an ECS so low as to be, on any view, harmless to humanity and to the planet.

Is there not one single Western government scientifically literate and politically courageous enough to face down the climate Communists and to reject in toto and latae sententiae the egregiously exaggerated claims and manifestly bogus mathematics of the screeching profiteers of doom?