A new Pause? – Watts Up With That?

By Christopher Monckton of Brenchley

At long last, following the warming effect of the El Niño of 2016, there are signs of a reasonably significant La Niña, which may well usher in another Pause in global temperature, which may even prove similar to the Great Pause that endured for 224 months from January 1997 to August 2015, during which a third of our entire industrial-era influence on global temperature drove a zero trend in global warming:

As we come close to entering the la Niña, the trend in global mean surface temperature has already been zero for 5 years 4 months:

However, the new Pause is at a surface-temperature plateau 0.3 C° above the old Pause:

That is equivalent to a not particularly terrifying centennial warming rate of 1.25 C° over the 19 years covering the two pauses and the warming in between.

Since the projected net anthropogenic radiative forcing over the 21^st century is approximately equivalent to the 3.5 W m^–2 forcing from doubled CO₂, the indications are that equilibrium sensitivity to a CO₂ doubling, known as equilibrium CO₂ sensitivity (ECS) or Charney sensitivity, is a great deal smaller than the 3 C° originally estimated by Charney in 1979 and the 4 C° projected by models. Let us test that proposition not with models but with data.

It is possible to derive ECS directly from observational data, with the help of the following handy equation. The anthropogenic equilibrium sensitivity ΔE_t over a given period from time t to time t +1 is the product of the anthropogenic fraction M of observed period global mean surface warming ΔT_t and the ratio of the period anthropogenic forcing ΔQ_t to the difference between ΔQ_t and the period anthropogenic fraction M of the Earth’s observed energy imbalance ΔN_t.

From 1850-1980, net anthropogenic forcing ΔQ₁ was 1.25 W m^–2 (IPCC 2013, fig. SPM.5). The Planck sensitivity parameter for 1850 was about 0.3 C° W^–1 m². Their product was the 0.37 C° period anthropogenic reference sensitivity ΔR₁ (i.e., the direct warming before adding feedback response). By coincidence, ΔR₁ was equal to the observed period warming trend ΔT₁ (HadCRUT4). Wu et al. (2019) give the anthropogenic fraction M of observed global warming as 0.7. Using the equation, period equilibrium sensitivity ΔE₁ was 0.39 C°. The system-gain factor A₁ = ΔE₁ / ΔR₁, which allows for feedback response, was just 1.005.

From 1980-2020, net anthropogenic forcing ΔQ₂ was 1.65 W m^–2 (NOAA AGGI index, 2020, adjusted for ozone, aerosols and black carbon). The product of that value and the Planck sensitivity parameter was the 0.49 C° period anthropogenic reference sensitivity ΔR₂. The observed period warming trend ΔT₂ (HadCRUT5) was 0.7 C°. For M = 0.7, the equation gives period equilibrium sensitivity ΔE₂ as 0.54 C°. The system-gain factor A₂ = ΔE₂ / ΔR₂ was 1.1.

Given the 3.5 W m^–2 radiative forcing ΔQ₃ equivalent to a doubling of CO₂ concentration (Zelinka et al. 2020) compared with that year, the reference sensitivity ΔR₃ to doubled CO₂ is 1.05 C°. Finally, to allow for nonlinear growth in feedback response with temperature, we need to know the approximate rate at which the system-gain factor increases over time. That is why we studied the two recent periods which, taken together, constitute the climatological industrial era. From 1850-1980 the system-gain factor was 1.05; from 1980-2020 it was 1.1. Therefore, a respectable approximation for the period following 2020 is 1.15.

Accordingly, midrange ECS – currently imagined to be 3.7 C° (Meehl et al. 2020) or even 3.9 C° (Zelinka et al. 2020), is actually 1.05 x 1.15, or 1.2 C°, very much in coherence with the 1.25 C° centennial-equivalent warming rate of the past 19 years.

Why, then, is the world panicking about global warming? The reason is that climatologists imagined that the 32 C° natural greenhouse effect, the difference between the 255 K emission temperature that would obtain in the absence of greenhouse gases and the 287 K surface temperature in 1850, comprised 24 C° preindustrial feedback response entirely attributable to the 8 C° reference sensitivity forced by the preindustrial noncondensing greenhouse gases.

They had not appreciated that most of the 24 C° preindustrial feedback response was not driven by the 8 C° preindustrial noncondensing greenhouse gases but by a quantity 30 times larger: namely, emission temperature itself. The feedback response to those gases was thus minuscule: probably less than 1 C° of the 24 C°. Sure enough, the feedback responses from 1850-1980, from 1980-2020 and from 2020 to doubled CO₂ work out at just 0.02 C°, 0.05 C° and 0.16 C° respectively. End of climate “emergency”.

It will be interesting to see how long the current Pause will endure. At the moment, we are not quite in formal La Niña conditions. In the table below, warm periods (shown in red) and cold periods (blue) are based on a threshold of ±0.5 C° in the Oceanic Niño Index, which is the three-month running mean of the ERSST v. 5 sea-surface temperatures in the Niño 3.4 region of the equatorial eastern Pacific from 5° North to 5° South of the Equator and from 120° to 170° West of the universal meridian.

Technically, a full-on El Niño (warming period: red) or La Niña (cooling period: blue) is only declared after five consecutive three-month periods above or below the ±0.5 C° threshold. So far, there have been four months below the lower threshold. If, as seems likely, the period from November to January also crosses the lower threshold, we shall be in a proper La Niña, which may endure for another few months, lengthening the Pause perhaps until the Glasgow climate conference this December. Watch this space.

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