Climate Sensitivity Considering Urban and Natural Warming
Guest Post
By Ken Gregory, P.Eng.
This blog post summarizes the paper Climate Sensitivity by Energy Balance with Urban and Natural Warming.
Climatologists Nicholas Lewis and Dr. Judith Curry published a paper in the Journal of Climate in (LC2018) that used the observationally-based energy balance method to estimate the Equilibrium Climate Sensitivity (ECS) and the Transient Climate Response (TCR). The ECS is the global average surface temperature change due to a doubling of CO2 after allowing the oceans to reach temperature equilibrium, which takes about 1500 years for the upper 3 km of the ocean. The TCR is more relevant to climate policy as it is the global surface temperature change at the time of the CO2 doubling.
Solar forcing may be several times larger than just that caused by the change in the total solar irradiance (TSI) as interpreted by the IPCC. A paper Scafetta et al 2019 shows that the TSI forcing was greater than that used in LC2018. The large variations of solar ultraviolet radiation affect ozone in the upper atmosphere which causes a significant solar forcing. High solar activity reduces cosmic rays entering the atmosphere, reducing lower cloud cover and causing warming by increased incoming solar radiation.
As it is difficult to quantify each of these forcings, temperature proxies are used to estimate the natural warming since the start of the base period by extrapolating the millennium scale temperature cycle. The surface temperature change should be revised downward to remove the natural warming from the Little Ice Age so that the temperature change used in the energy balance calculations includes only the portion that was caused by the change in anthropogenic forcing.
Fredrik Ljungqvist prepared a temperature reconstruction of the Extra-Tropical Northern Hemisphere (ETNH) during the last two millennia as shown in figure 1. Human-caused GHG emissions did not cause significant temperature change to the year 1900 because cumulative CO2 emissions to 1900 were insignificant. Extrapolations of the millennium cycle from 1900 to 2010 provide an estimate of the natural component of the temperature change.
The global temperatures changed by 75% of the ETNH temperatures from 1900-1919 to 2002-2015. The global natural temperature change between the base and final periods of the LC2018 analysis is estimated at 0.084 °C/century. The temperature changes used in the climate sensitivity calculations must be reduce by 0.114 °C to account for natural climate change.
Numerous papers have shown that the UHIE contaminates the instrument temperature record. Most long-term temperature records are recorded in or near cities which have gotten warmer as they grow. A study by McKitrick and Michaels 2007 showed that about half of the warming over land since 1980 in instrument data sets is due to the UHIE. The global UHIE is about 0.041 °C/decade. A paper by De Latt and Maurellis shows the global UHIE is 0.040 °C/decade. These studies are supported by numerous other studies. The temperature change used in the LC2018 climate sensitivity calculations must be reduce by 0.133 °C to account for the UHIE from 1979.
The millennium cycle natural warming and UHIE corrections reduce the temperature change between the two periods of the LC2018 analysis due to GHG by 0.247 °C. The best estimates of ECS and TCR are 1.04 °C and 0.83 °C, respectively.
The probability density functions (PDF) of the LC2018 ECS and TCR were replicated for this study. Standard deviations and CIs were assigned to factors used to calculate the millennium cycle and UHIE adjustments to determine a PDF for the corrected ECS estimates. Figures 2 and 3 show the LC2018 PDF and the corrected PDF of ECS and TCR, respectively.
The forecast of global temperature rise from 2019 due to anthropogenic GHG emissions assumes that atmospheric CO2 concentrations continue to increase at the current rate of 0.60%/year and that non-CO2 GHG continue to contribute 18% of the CO2 forcing.
This estimate includes the effects of increasing GHG concentration prior to 2019. Actual temperatures may rise or fall depending on natural climate change. Figure 4 shows the projected temperature response to continued exponential growth in GHG concentrations. The 2019-2100 temperature rise is 0.63 °C with a likely 17-83% range of 0.51 to 0.79 °C.
A paper published in Energies by Peter Lang and me shows that the impact of a 3 °C temperature rise from 2000 on USA energy expenditures would have a positive impact on USA economic wealth of +0.07% of gross domestic product (GDP). A paper by me (Gregory 2020) extends the analysis to global impacts. A paper by Dayaratna, McKtrick & Michaels recommends that the CO2 fertilization effect in the FUND economic model be increased by 30% due to recent studies of the effect. Incorporating these two changes in FUND and using an ECS of 1.0 °C shows that a 2 °C global mean surface temperature rise from 2000 would increase global wealth by 1.45% in 2147, equivalent to 2019US$1.26 trillion.
CO2 emissions have a large social benefit, so policies to restrict CO2 emissions are harmful and misguided. The paper contains more information, details of the calculations and a link to an Excel file.
This the Abstract of Ken’s paper:
Comments are closed.
NOT A LOT OF PEOPLE KNOW THAT 
It is not possible to understand or to study global warming in terms of both the ECS and the TCR because of a mathematical inconsistency issue.
It has to be one or the other.
It can’t be both.
https://tambonthongchai.com/2020/08/26/a-mathematical-inconsistency/
Yes chaamjamal,
Mathematical and a physical inconsistency as they both rely on the idea that the climate has both constancy and consistency — neither is true.
Climate as the IPCC acknowledge in TAR Chap 14, Exec Summary “…we should recognise that we are dealing with a coupled non-linear chaotic system, and therefore that the long-term prediction of future climate states is not possible.”
– IPCC TAR Chap 14, Exec Summary
In trying to calculate Equilibrium Climate Sensitivity (ECS) and the Transient Climate Response (TCR) all parameters within the chaotic climate system would have to be known (known about its past and how all parameters are currently). None of this is possible, none of it is known to a level of completeness or accuracy to allow such calculations.
The ECS and TCR approximations that are done have within them huge error bars and many simplifications of climate parameters that are of dubious merit.
It is as if they can make a calculation of the average speed of a journey that they do not accurately know how it started and is still proceeding — it is irrational nonsense.
Well said. Good insights. Thank you.
ECS and TCR are not mathematical inconsistent. They are different metrics of climate sensitivity. ECS is the temperature change after a doubling of CO2, then waiting for thousands of years for the oceans to reach temperature equilibrium. TCR is the temperature change at the time of a doubling of CO2 where the increase is 1% per year, which is very close to the value where the increase is at the current rate of CO2 increase. You need to know both values to generate a temperature forecast.
Thank you for your comment sir. Agree to disagree I guess. Cheers.
ECS is a popular myth, based on false assumptions about the non-existent dominance of radiative properties of the atmosphere in determining temperature.
Why no interest in atmospheric pressure and the lapse rate, common to all solar system bodies with a significant atmosphere?
“CO2 emissions have a large social benefit, so policies to restrict CO2 emissions are harmful and misguided.”
Rapid restriction of fossil fuel emissions has already damaged global economies, as the pandemic travel lockdown demonstrates. But where does this leave all the efforts to capture and store CO2 by negative emission technology…the path to NET-zero? That entire CCS industry will not go quietly. Nor will the green deal zealots.
Their use of decimal points shows they have a sense of humour.
Humour is a good thing, and in a certain sense I agree.
However, doing things with numbers requires some degree of practicality and restraint.
Choices have to be made, for example, with something as seemingly simple as reporting the length of a coastline.
https://brilliantmaps.com/gb-coastline/
In the report of this post, give the author credit for NOT showing all the digits supplied by the computer doing double precision arithmetic. Three seems to be a practical choice.
If you wish to believe that any part of this:
‘The global natural temperature change between the base and final periods of the LC2018 analysis is estimated at 0.084 °C/century. The temperature changes used in the climate sensitivity calculations must be reduce by 0.114 °C to account for natural climate change.’
. . . bears any resemblance to reality, go right ahead.
I choose to smile.
The estimates of ECS, TCR and temperature change are all probabilistic estimates. They have wide 5 – 95% ranges due to uncertainty. Therefore the number of decimal points used to describe the median estimate of ECS and TCR is no practical relevance.
Natural climate change has a large chaotic component which makes an estimate of temperature change that includes natural factors problematic. ECS and TCR estimate do not have a chaotic component. The temperature forecast in the paper specifically excludes natural climate change so the forecast is not chaotic.
I am sure we will see a full and comprehensive discussion of this paper and it’s far from secret contents on the BBC given their “impartial” credentials…..
I have been looking at datasets obtained by separating rural and urban temperature measurements (pre or without hermogenization) including the NOAA USCRN data, JMA data covering Japan and Central China, and papers using raw data from Arctic and Antarctic, where of course urban heating is not a problem. All show that, without UH and homogenization, there have been long periods without warming. There are two exceptions, Greenland and the geothermal area of Eastern Antarctica. This implies no greenhouse warming at all.and suggests to me that the relevant windows of IR are saturated. I find it difficult to reconcile this with significant values of ECS in particular.
Incidentally it would be interesting to see Urban and Rural datasets of the UK. Has anybody done this?
Yeah, I get an ECS of about 0.7 C/doubling using HadCET…with the historical indirect solar influence based on Butler & Johnston 1996 (Amargh Observatory data).
The point is the climateers add in all the warming influences and say all of it is due to CO2. Whereas in reality a lot is due to the Sun, and some is due to the thermohaline cycle, since the IPCC cutely takes their model training century from the bottom of the cycle in 1906 and ends at the top of the cycle in 2005.
It’s a tell that the only model to roughly fit the AMSU satellite and radiosonde data is the Russian model, which includes the cycles. All the rest are ‘way too high because they have a ‘way too high 2XCO2 factored in them.
Of course the problem for the climateers is that any ECS less than 1 C/doubling is completely harmless, since it’s a logarithmic response. There isn’t enough extractable carbon to cause dangerous warming if ECS is below 1 C/doubling.