Following Arrhenius on global warming

But he did change his mind …

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This 1912 newspaper article (right) shows that a century ago the worthy citizens of Warkworth were followers of Svante Arrhenius’s new theory that global warming would be caused by mankind’s emissions of greenhouse gases.

Forty years earlier Tyndall had identified CO2 as a greenhouse gas. Arrhenius followed up with newly available data in 1896 and calculated that doubling CO2 would increase temperatures by 5°C or 6°C. In 1906 he reduced it to 4.0°C.

Arrhenius is frequently cited by warmsters chiding sceptics for their lack of belief, telling them, “Science has known about dangerous warming for 120 years.” But science knew nothing of dangerous warming, because Arrhenius showed none. He was free of the modern pathological aversion to carbon dioxide (the gas of life) because he saw no reason to object to it.

Benefits from CO2 indisputable

Tyndall and Arrhenius were drawn to investigating ice ages and thought CO2 could trigger them, while man-made emissions might also prevent them. He knew that CO2 was necessary for plant growth as well, so he had no concerns about the gas and thought whatever warming ensued would be beneficial.

Much scientific discussion took place after 1896 and some rejected any effect of CO2. Arrhenius published a paper in German amending his view of increased CO2 on climate, lowering his estimates by several degrees and saying any warming would be beneficial. It was not translated at the time though it was widely known by European scientists.

Since Arrhenius’s paper in 1896, man-made emissions of carbon dioxide have increased 18-fold, from 2 billion tons a year to 36 billion tons, yet global temperatures have barely moved — about 0.8°C, much of it from natural variability. Successive IPCC Assessment Reports have moved the warming steadily downwards as earlier forecasts proved too hot.

Planning an electricity substation near the coast or a stormwater outfall on the beach must be a nightmare for engineers. They have to redraw their plans every few years to accommodate the changing predictions of sea level. Meanwhile, the rate of sea level rise has remained unchanged for a hundred years. Anyway, here is the predicted 2100 warming from the Executive Summaries in the five assessment reports.

Note

The first assessment report (FAR) used the term “prediction” to describe the model outputs, but that was the first and last time. Scientists complained about the use of unverified computer models being treated as data. Extrapolation from observations might correctly be called predictions, but unvalidated model output, which may be well informed, is yet no better than a guess. Strong criticism by an expert reviewer, the late New Zealand scientist Vincent Gray, restrained the IPCC’s use of the term “prediction” rather than the proper term “projection” — as, he told us, they had agreed.

All five Assessment Reports

FAR – 1990

Under the business-as-usual scenario (Scenario A), the IPCC predicted warming of 3°C before 2100.

SAR – 1995

Under the mid-range scenario (IS92a) the IPCC projected warming of about 2°C by 2100.

TAR – 2001 (the Hockey Stick on page 3!)

IPCC said warming would be up to 5.8°C by 2100. Big jump, this.

AR4 – 2007 (no Hockey Stick, not seen again)

The IPCC’s “best estimate” of warming was up to 4.0°C by 2100.

AR5 – 2013

The IPCC forecasts up to 4.8°C from the ludicrous RCP8.5 scenario because it assumes we burn all the coal the earth contains, which is preposterous. Besides that, they expect warming of up to 3.1°C by 2100. – Table TS.1 p. 90

Lingering ambiguities

In the translation of Arrhenius’s 1906 Amended View of The Probable Cause of Climate Fluctuations are several mutually contradictory statements of warming. I couldn’t fully discriminate between them, so perhaps you can help. Page 6 says:

I calculate that a reduction in the amount of CO2 by half, or a gain to twice the amount, would cause a temperature change of – 1.5 degrees C, or + 1.6 degrees C, respectively.

Further, pages 7 & 8 have these contradictory statements.

one finds that with a change in the quantity of CO2 in the ratio of 1:2, the temperature of the Earth’s surface would be altered by 2.1 degrees.

the total temperature change induced by a decrease in CO2 in the air by 50% is 3.9 degrees (rounded to 4 degrees C).

The topic is fascinating and shows that after a hundred years we pesky sceptics are still unconvinced. If only they’d throw us some evidence, we could go away!

 

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