Assuming the logarithmic diminution premise to be appropriate, this diagram indicates:
- there is no direct, straight-line relationship between atmospheric CO2 concentration and its influence on temperature
- 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 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 taken up.
- 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: this calculation takes no account of feedbacks, which are undeterminable
- a rise of +0.35°C would be so marginal as to be undetectable within the noise of Global temperature measurements
- such a further doubling of atmospheric CO2 to ~820ppmv would take more than 150 years at the present rate of CO2 emissions
- cooling of the Oceans, again re-absorbing CO2 from the atmosphere is the only way that atmospheric CO2 levels will reduce: that can only be in a coming ~100,000 year glaciation.
- life on Earth is dependent on its atmospheric CO2 used by plants via photosynthesis to release oxygen and generate organic compounds
- as the present Holocene interglacial epoch advanced the planet warmed, so warmer Oceans out-gassed CO2 to reach a pre-industrial level of about 280ppmv
- that slow CO2 out-gassing process from warmer Oceans is continuing and has been supplemented largely by Man-made CO2 emissions since the 1850s from the burning of fossil fuels: the measured CO2 level has now reached about 410ppmv
- Water vapour and clouds in the atmosphere are responsible for the greatest part of the Greenhouse effect
- CO2 is a significant “Greenhouse Gas”, even though it is only present in trace amounts, (now ~410 parts per million by volume)
- CO2 is considered to be responsible for roughly 10% of the total +~33°C “Greenhouse” effect or about +3.3°C
- plant productivity improves radically with increasing atmospheric CO2 and NASA has reported ~+15% more green growth worldwide over the last 50 years, enhancing agricultural productivity and enabling the food supply for a growing Global population
- plant productivity is hampered by colder weather and any cooling will lead to agricultural losses.
- photosynthesis stops and plants and thus life on Earth can no longer survive if atmospheric CO2 concentration falls below 150 ppmv
when plants evolved, atmospheric CO2 levels were very much higher than at present (~10-20 times) and no runaway Global warming occurred.
- those high levels of CO2 atmosphere have progressively been reduced, with CO2 both being absorbed by the Oceans to be sequestered as limestone by Ocean life or converted into fossil fuels
- only some 20,000 years ago, in the depths of the last ice age, Life on Earth came very close to total annihilation when atmospheric CO2 concentration fell to 180 ppmv, only ~15% above its terminal value:
this process is driven by colder Oceans being able to absorb more atmospheric CO2 and that carbonate being progressively sequestered 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 extends the viability of Life on Earth.
This arithmetic shows that Man-made additions of CO2 to the atmosphere can only have very marginal further temperature effect into next century and beyond.
Climate modellers assert that there is substantial positive temperature feedback from the warming induced by added CO2 which could increase the level of water vapour in the atmosphere. In order to reach the much feared +2°C temperature increase that feedback from water vapour and clouds would have to be more than 5-fold or even more to achieve their higher predictions. There is no evidence of such positive feedbacks and observations show feedback is likely to be marginally negative.
This simple maths and the fact that the warming effect of CO2 is close to being saturated shows that any level future of atmospheric CO2 increased by Man-kind’s burning of fossil fuels can never cause Catastrophic Global Warming.