Conversation

between @BerkeleyEarth and @ncdave4life.

a year ago

Berkeley Earth@BerkeleyEarth

There has been a close correlation between changes in global temperature and the rise of carbon dioxide in the atmosphere during the last 170 years.

To limit global warming this century, we need to limit CO₂ emissions.

An animated history of temperature vs. carbon dioxide.

Berkeley Earth@BerkeleyEarth

Static plot showing the correlation between global mean temperature and carbon dioxide concentration in the atmosphere over the last 170 years.

Berkeley Earth@BerkeleyEarth

Final frame of the animation. If carbon dioxide concentrations keep rising at historical rates, global warming could more than triple this century.

We need to limit carbon dioxide to limit global warming. Even so, some further warming is already unavoidable.

Dave Burton ❌@ncdave4life

[1/11] BEST's figures imply MUCH LOWER climate sensitivity than IPCC claims.

You show, "About 2.3°C of warming per doubling of CO2 (ignoring the role of other greenhouse gases and forcings)."

But to deduce climate sensitivity (to CO2), you CANNOT ignore other GHGs.
[cont'd]

Dave Burton ❌@ncdave4life

[2/11] Even if we assume that none of the warming is natural, if 30% of the warming is due to increases in minor GHGs like O3, CH4, N2O & CFCs, then "climate sensitivity" from a doubling of CO2, according to BEST's figures, is only 0.7 × 2.3 = 1.6°C.
[cont'd]

Dave Burton ❌@ncdave4life

[3/11] That's a "practical estimate" of climate sensitivity, from surface station measurements. However, if the best satellite data were used, instead of BEST's surface temperatures, sensitivity would be almost 30% lower:
 https://woodfortrees.org/plot/best/from:1979/mean:12/plot/uah6/from:1979/mean:12/plot/best/from:1979/trend/plot/uah6/from:1979/trend 
 https://sealevel.info/BEST_vs_UAH_2020-06-14h_digitization_notes.txt 
[cont'd]

Dave Burton ❌@ncdave4life

[4/11] That makes climate sensitivity to a doubling of CO2 only 1.23°C.

Since that's based on real-world forcing (instead of the faster rise used for the TCR definition), the 1.6°C or 1.23°C per doubling is "between TCR & ECS" (probably about an average of TCR & ECS).
[cont'd]

Dave Burton ❌@ncdave4life

[5/11] ECS is usually estimated at 1.25× to 1.6× TCR. So:

If 1.6°C is avg of TCR & ECS, it means TCR is 1.23 to 1.42°C, and ECS is 1.77 to 1.97°C.

If 1.23°C is avg of TCR & ECS, it means TCR is 0.95 to 1.09°C, and ECS is 1.37 to 1.51°C.

See:  https://sealevel.info/BEST_vs_UAH_2020-06-14h_digitization_notes.txt 
[cont'd]

Dave Burton ❌@ncdave4life

[6/11] That gives an overall TCR range of 0.95 to 1.42°C, and an overall ECS range of 1.37 to 1.97°C.

Those sensitivities are obviously FAR BELOW the assumptions baked into most CMIP6 models and IPCC reports, which means their warming projections are much too large.
[cont'd]

Dave Burton ❌@ncdave4life

[7/11] You say, "About 1.1°C of warming has already occurred," and "if carbon dioxide concentrations keep rising at historical rates, global warming could more than triple this century."

That's wrong, for two reasons.
[cont'd]

Dave Burton ❌@ncdave4life

[8/11] 1. It assumes WILDLY accelerated warming, from an approx linear continuation of forcing, for which there's no basis. Even BEST's 0.192°C/decade yields only 1.536°C of add'l warming by 2100. UAH6's 0.134°C/decade yields only 1.072°C by 2100.
 https://www.sealevel.info/co2.html?co2scale=2 
[cont'd]

Dave Burton ❌@ncdave4life

[9/11] 2. It assumes an implausible continuation of exponentially increasing CO2 level growth (necessary for continuation of the linear trend in forcing). But resource constraints ensure the forcing trend will fall below linear long before 2100.
 https://www.researchgate.net/publication/303621100_The_implications_of_fossil_fuel_supply_constraints_on_climate_change_projetions-A_supply-side_analysis 
[cont'd]

Dave Burton ❌@ncdave4life

[10/11] Also, negative feedbacks (mainly terrestrial "greening," and oceans) are removing CO2 from the air at an accelerating rate.
 https://sealevel.info/feedbacks#greening 
So (unfortunately!) it's unlikely that mankind's use of fossil fuels can ever drive CO2 level above 700 ppmv.
[cont'd]

Dave Burton ❌@ncdave4life

[11/11] Since CO2 forcing trend log(level) is almost certain to fall below linear later this century, rate of temperature increase, which is already too slow to reach the temperatures you project, should slow BELOW even the current slow 0.134°C to 0.192°C/decade linear trend.
###

Dave Burton ❌@ncdave4life

do you not have have any comment on the fact that your data implies a much lower climate sensitivity to rising CO2 levels than the IPCC claims?

Dave Burton ❌@ncdave4life

are you there?

@RichardAMuller @stevenmosher @RARohde @hausfath @JudithSissener @BerkeleyPhysics

Dave Burton ❌@ncdave4life

will you please reply?

The temperature measurements imply TCR between 0.95 & 1.42°C, and ECS between 1.37 & 1.97°C. Will you at least acknowledge that your measurements imply climate sensitivity well below IPCC estimates?
 https://sealevel.info/twitter_BerkeleyEarth_1265595986942058497_screenshot03.png 

Dave Burton ❌@ncdave4life

team: @RichardAMuller, @stevenmosher, @RARohde, @hausfath, @JudithSissener

Will you please acknowledge that your data shows ECS climate sensitivity to a doubling of CO2 is <2°C, and TCR is <1.5°C?

@BerkeleyPhysics, how about a response?

 https://sealevel.info/learnmore.html 




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