A low estimate of Climate Sensitivity


This note carries out simple “back of the envelope calculations” for Climate Sensitivity, the Global temperature effect of doubling of atmospheric CO2 concentration from the current 410ppmv up to 820ppmv. 


The calculation takes no account of any possible feedbacks, which might enhance but may even reduce the temperature effect of added CO2:  the value for feedback is indeterminate.

This posts assesses CO2 as being ~10% of the greenhouse effect, Climate Sensitivity results in a value, (~+0.35°C), this is a value within the bounds of error of any temperature measurement.  This low result is about 1/3rd of other more mainstream Climate Sensitivity values.

However, if this result is anywhere close to reality, or even at 3 times that level (~1.0°C) this result means that:

  • there is no real overheating problem with the further Man-made emissions of CO2 from the continued burning of fossil fuels.
  • the whole Global Warming / Climate Change agenda is a fabrication supported only by quasi-religious beliefs in the evils of industrial society and / or a political agenda intended to undermine Western capitalism.



The assumptions used to make these “back of the envelope calculations” are as follows:

  • the Earth’s Greenhouse effect sustains Global temperature by ~+33°C
  • CO2 is considered to be responsible for roughly 10% of the total “Greenhouse” effect or about +~3.3°C:  IPCC authors quote the range to be from 2% – 25%, so 10% is a reasonable median value
  • CO2 is a significant “Greenhouse Gas”, even though it is still only present in trace amounts, now ~410 parts per million by volume, (ppmv)
  • at 400ppmv CO2 concentration is about an order of magnitude lower than its earlier values when plants evolved
  • logarithmic diminution operates for CO2 doubling concentration across the full range of CO2 concentration values
  • the resulting increase due to doubling CO2 concentration is about +~0.35°C

This diagram, in 20ppmv increments, indicates that:

Screenshot 2020-09-10 at 10.40.33.png
  • there is not a direct, straight-line relationship between atmospheric CO2 concentration and its influence on temperature
  • accordingly, the “Greenhouse” warming effectiveness of CO2 diminishes logarithmically with increasing concentrations, which implies as a result:
    • at 20ppmv, ~42% of CO2 warming effectiveness is already taken up
    • at 100ppmv, ~67% of CO2 warming effectiveness is taken up
    • at 150ppmv, the CO2 level of plant / planet viability, ~72% of CO2 warming effectiveness is taken up
    • at 280ppmv, the approximate long-term pre-industrial CO2 level, ~82% of CO2 warming effectiveness is taken up
    • at the current level of atmospheric, CO2 410ppmv ~88% of CO2 warming effectiveness is already taken up
    • any doubling across the logarithmic diminution scale results in the same temperature effect of ~+0.35°C.
  • Equilibrium Climate Sensitivity, (ECS), is assessed as the further temperature increase that arises from a doubling of CO2 in the atmosphere
  • the logarithmic diminution graph shows that a doubling of CO2 from 410ppmv to 820ppmv should result in a temperature increase of about ~+0.35°C, because the warming capability of CO2 is now so close to saturation
  • at the current CO2 rate of emissions growth, ~2.5ppmv/year, this transition to doubling present CO2 concentration could take ~150 years.
  • this “back of the envelope calculation” takes no account of feedbacks



CO2 in the atmosphere

Take note of the history of the Earth’s atmosphere over 4.6 billion years:

  • the maximum CO2 concentration experienced on Earth was ~ 35%, 350,000ppmv, about 3.3 billion years ago.  The CO2 level is now reduced to a mere 400parts / million by volume, 0.04%
  • any temperature comparisons between the growing bu still trace levels of CO2 on Earth and the atmosphere of Venus, at virtually 100% CO2 and being much closer to the sun are erroneous
  • from 3.5 billion years ago onwards, that high level of CO2 atmosphere has progressively reduced, with CO2 both being absorbed by the Oceans to be sequestered as limestone by Ocean life or later converted into fossil fuels from luxuriant plant growth
  • nonetheless, even at its current low level, 400ppmv, Life on Earth is still entirely dependent on atmospheric CO2, used by plants via photosynthesis to release oxygen and generate organic compounds
  • photosynthesis stops and plants and thus Life on Earth can no longer survive if atmospheric CO2 concentration falls below 150 ppmv
  • only 20,000 years ago, in the depths of the last ice age, all Life on Earth came close to total annihilation when atmospheric CO2 concentration fell to 180 ppmv, only ~15% above the terminal value of 150 ppmv:
    • this process is driven by colder Oceans absorbing more atmospheric CO2 and that carbonate being progressively sequestered over millennia by marine life as limestone.
    • this is the way that all Life on Earth will be extinguished in some future ice age due to atmospheric CO2 starvation.
    • so, all extra CO2 in the atmosphere has the potential to slow these processes and extend the viability of Life on Earth.
  • in the recent past, in the last 12,000 years, as the present Holocene interglacial epoch has advanced, Earth warmed, so warmer Oceans out-gassed CO2 to approach a pre-industrial level of ~300ppmv
  • that slow and deferred CO2 out-gassing process from warming Oceans is continuing and has been supplemented by Man-made CO2 emissions since the 1850s from the burning of fossil fuels
  • with these two CO2 sources in combination, CO2 level has now reached ~410ppmv
  • when plants evolved, atmospheric CO2 levels were very much higher and no runaway Global warming occurred
  • the logarithmic diminution effect is confirmed by the absence of any runaway warming at much higher previous CO2 levels
  • plant productivity improves radically with increasing atmospheric CO2 and NASA has already reported ~+15% more green growth Globally over the last 50 years, enhancing agricultural productivity and enabling the food supply for a growing World population
  • plant productivity is hampered in colder weather: any cooling would lead to agricultural losses
  • with cooling, the temperature differential between the tropics and the poles increases and with that greater energy differential Weather will deteriorate
  • the only way that atmospheric CO2 levels will ever reduce is by the cooling of the Oceans, again being able to re-absorb CO2 from the atmosphere: that can only occur in some coming ~100,000 year glacial period.
  • as the undeveloped world advances its level of development with coal-firing for electricity generation and more mobility, atmospheric CO2 levels will increase and whatever actions are taken in the Western World will be overtaken by their release of CO2.

Quantifying Futility: 2020 estimate of future CO2 emissions

  • all efforts by the West at CO2 reduction are thus futile, inducing massive economic self-harm.


Climate Models

This arithmetic shows that Man-made additions of CO2 to the atmosphere can only have very marginal further temperature raising effect into next century and beyond.

Climate modellers assert that there is very substantial positive temperature feedback from the warming induced by added CO2, which could increase the level of water vapour in the atmosphere, inducing secondary warming from the added effect of additional Water in the atmosphere. This assertion is unproven.

On this basis in order to reach their much feared +2°C temperature increase that feedback from water vapour and clouds would have to be more than 5-fold or even greater to achieve their higher predictions.  There is no evidence of such positive feedbacks and observations show feedback is likely to be marginally negative. 

IPCC / Academic climate models, presently used to set climate policy, are misleading for policy makers because they consistently overestimate the effects of further added Man-made CO2.

The remaining warming effect from Man-kind’s CO2 emissions may well be as low as is shown here.  The level of their potential error should at least give policy makers pause for thought, whilst mandating their destructive attempt to eliminate the use of Fossil fuels, particularly in the Western world.




If this low estimate of Climate Sensitivity is anywhere close to reality, it should give Policy Makers real cause to question their draconian reactions to the Man-made Climate Change problem:  it shows that Man-made CO2 emissions is not an existential problem for Man-kind at all.

So any further Man-made CO2 emissions are probably a non-problem for increasing Global temperature.  And those added CO2 emissions are inevitable as the undeveloped world progresses.

All levels of future of atmospheric CO2 increased by Man-kind’s burning of fossil fuels will be virtually immaterial for Global Temperature, when all added Man-made CO2 emissions can only ever cause slight further Global Warming. 

This trivial maths and the fact that the temperature enhancing effect of added CO2 is so close to being exhausted means that further Man-made CO2 emissions are virtually ineffective temperature-wise.

Now any CO2 heating effect is likely to be subsumed this century by the current ongoing reduction of Solar activity and the later coming but inevitable end of our current warmer and benign Holocene interglacial. 

In the meantime Man-made emissions of CO2 bring positive advantages:

  • In Mankind’s history warmer periods have always been times of growth and prosperity, whereas colder times have lead to pestilence and starvation.
  • Added minor warmth is advantageous to the biosphere and to Man-kind: cold deaths are much higher than deaths from overheating. 
  • Additional atmospheric CO2 is very beneficial for plant growth and thus agricultural productivity:  horticulturists use concentrations of 1200 parts / million or more for better productivity in their heated greenhouses.
  • Any extra CO2 from Man-made emissions from burning Fossil Fuels may even extend the viability of all Life on Earth by deferring the CO2 starvation, that is likely to occur in some future 100,000 year glaciation.