Here’s another guest post from Ed Hoskins. This one deals with the IPCC’s own figures fro the effect of CO2 on global tamperature, demonstrating that due to the logarithmic limitation as this trace gas increases, future warming will be limited to within beneficial limits.
The diminishing influence of increasing Carbon Dioxide CO2 on temperature
Ed Hoskins MAarch (Cantab) BDS (Lond).
The temperature increasing capacity of atmospheric CO2 is theoretically plausible, but its influence is known and widely accepted to diminish as its concentration increases. It diminishes logarithmically with increasing concentration.
Global Warming advocates and Climate Change sceptics both agree on this. IPCC Published reports, (TAR), acknowledge that the effective temperature increase caused by growing concentrations of CO2 in the atmosphere radically diminishes with increasing concentrations. This information has been presented in the IPCC reports. It is well disguised for any lay reader, (Chapter 6. Radiative Forcing of Climate Change: section 6.3.4 Total Well-Mixed Greenhouse Gas Forcing Estimate) [i].
It is a crucial fact, but not acknowledged in the IPCC summary for Policy Makers[ii]. The rapid logarithmic diminution effect is an inconvenient fact for Global Warming advocates and alarmists, nonetheless it is well understood within the climate science community. It is certainly not much discussed.
This diminution effect is probably the reason there was no runaway greenhouse warming caused by CO2 in earlier eons when CO2 levels were known to be at levels of several thousands ppmv. The following simplifying diagram shows the logarithmic diminution effect using tranches of 100ppmv up to 1000ppmv and the significance of differing CO2 concentrations on the biosphere:
- Up to ~200 ppmv, the equivalent to about ~77% of the temperature increasing effectiveness of CO2. This is essential to sustain photosynthesis in plants at all and thus the viability of all life on earth.
- A further ~100 ppmv was the level prior to any industrialisation, this atmospheric CO2 made the survival of the biosphere possible, giving a further 5.9% of the CO2 Greenhouse effect.
- Following that a further 100ppmv, (certainly man-made in part), adding ~4.1% of the CO2 effectiveness brings the current level ~400 ppmv.
- CO2 at 400pmmv is already committed and immutable. So CO2 has already reached about ~87+% of its potential warming effect in the atmosphere.
- 400-500 ppmv 3.23%
- 500-600 ppmv 2.64%
- 600-700 ppmv 2.23%
- 700-800 ppmv 1.93%
- 800-900 ppmv 1.71%
- 900-1000 ppmv 1.53%
So now at 400ppmv only ~13% of the effectiveness of CO2 as a Greenhouse Gas now remains even up to the level of ~1000ppmv.
Both sceptics and the IPCC publish alternate views of the reducing effect on temperature of the importance of CO2 concentration. These alternates are proportionally equivalent but vary in the degree of warming attributable to CO2. The IPCC have published the following views of the total effect of CO2 as a greenhouse gas up to ~1200ppmv, they range in temperature from +6.3°C to +14.5°C, shown below:
Other views are presented both by sceptical scientists and CDIAC, the Carbon Dioxide Information and Analysis Centre. What these different analysis show the is the amount of future warming that might be attributed to additional atmospheric CO2 in excess of the current level of ~400ppmv is truly marginal.
Looking to the future in excess of 400ppmv, wide variation exists between the different warming estimates up to 1000ppmv. A comparison between these estimates are set out below in the context of the ~33°C total Greenhouse Effect.This graphic shows in orange the remaining temperature effect of CO2 that could be affected by worldwide global decarbonisation policies, from 400ppmv up to 1000ppmv, according to each of these alternative analyses.
Some of the IPCC data shows very large proportions of the temperature effect attributable solely to the currently existing levels and any extra CO2. The concomitant effect of those higher levels of warming from atmospheric CO2 is that the proportion of the total ~33°C then attributable the water vapour and clouds in the atmosphere is displaced so as to be unrealistically low at 72% or 54%. It has to be questioned whether it is plausible that CO2, a minor trace gas in the atmosphere, currently at the level of ~400ppmv, 0.04% achieves such radical control of Global temperature, when compared to the substantial and powerful Greenhouse Effect of water vapour and clouds in the atmosphere?
There are the clearly divergent views of the amount of warming that can result from additional CO2 in future, but even in a worst case scenario, whatever change that may happen can only ever have a marginal future effect on global temperature.
Whatever political efforts are made to de-carbonize economies or to reduce man-made CO2 emissions, (and to be effective at temperature control those efforts would have to be universal and worldwide), those efforts can only now affect at most ~13% of the future warming potential of CO2 even up to the currently unthinkably high level of 1000ppmv.
So increasing CO2 in the atmosphere can not now inevitably lead directly to much more warming and certainly not to a catastrophic and dangerous temperature increase.
Importantly as the future temperature effect of increasing CO2 emissions can only be so minor, there is no possibility of ever attaining the much vaunted political target of less than +2.0°C by the control of CO2 emissions.
Global Warming advocates always assert that all increases in the concentration of CO2 are solely man-made. This is not necessarily so, as the biosphere and slightly warming oceans will also outgas CO2 over the long term. In any event at ~3% of the total[iii] Man-made CO2 at its maximum is only a minor part of the natural CO2 transport within the atmosphere. The recent IPCC report now admits that
currently recently increasing CO2 levels temperatures are probably only ~50% [or more] man-made.
“It is extremely likely [95 percent confidence] more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in greenhouse gas concentrations and other anthropogenic forcings together.”
This leads us to the bizarre conclusion that the IPCC is 95% certain that 50.001% of the warming is due to humans, and equally it is 95% certain that 100% of the warming is due to humans.
On the other hand, the data tells sceptics it is likely that any current global warming and increased CO2, if it is continuing, is:
- largely a natural process
- within normal limits
- probably beneficial.
It could be not be influenced by any remedial decarbonisation action, however drastic, taken by a minority of nations. In a rational, non-political world, that prospect should be greeted with unmitigated joy. If it is so:
- all concern over CO2 as a man-made pollutant can be entirely discounted.
- it is not essential to disrupt the economy of the Western world to no purpose.
- the cost to the European economy alone is considered to be ~ £165 billion per annum till the end of the century, not including the diversion of employment and industries to elsewhere: this is deliberate economic self-harm that can be avoided: these vast resources could be spent for much more worthwhile endeavours.
- were warming happening, unless extremely excessive, it provides a more benign climate for the biosphere and mankind.
- any extra CO2 is already increasing the fertility of all plant life on the planet.
- if warming is occurring at all, a warmer climate within natural variation would provide a future of greater opportunity and prosperity for human development, especially so for the third world.