Guest essay by Ed Hoskins
Using data published by the IPCC on the diminishing effect of increasing CO2 concentrations and the latest proportional information on global Man-made CO2 emissions, these notes examine the potential for further warming by CO2 emissions up to 1000ppmv and the probable consequences of decarbonisation policies being pursued by Western governments.
The temperature increasing capacity of atmospheric CO2 is real enough, but its influence is known and widely accepted to diminish as its concentration increases. It has a logarithmic in its relationship to concentration. Global Warming advocates and Climate Change sceptics both agree on this.
IPCC Published reports, (TAR3), 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) [1]. It is a crucial fact, but not acknowledged in the IPCC summary for Policy Makers[2].
 |
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 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.
Both sceptics and the IPCC publish alternate views of the reducing effect on temperature of the importance of CO2 concentration. These alternates are equivalent proportionally but vary in the degree of warming attributable to CO2.
The IPCC have published 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:
There are other views 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. Looking to the future in excess of 400ppmv, wide variation exists between the different warming estimates up to 1000ppmv, see below.
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 up to 1000ppmv that could be affected by worldwide global decarbonisation policies according to each of these alternative analyses.
Some of the IPCC data sets shows very large proportions of the temperature effect attributable solely to 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% up to 0.10% 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 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[3].
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. In any event at ~3% of the total[4] Man-made CO2 at its maximum is only a minor part of the CO2 transport within the atmosphere. The recent IPCC report now admits that currently increasing CO2 levels are probably only ~50% man-made.
On the other hand it is likely that any current global warming, if continuing and increased CO2 is:
§ largely a natural process
§ within normal limits
§ probably beneficial up to about a further 2.0°C+ [5].
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:
· concern over CO2 as a man-made pollutant can be mostly 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 excessive, it provides a more benign climate for the biosphere and mankind.
· any extra CO2 has already increased 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.
De-carbonisation outcomes
To quantify what might be achieved by any political action for de-carbonization by Western economies, the comparative table below shows the remaining effectiveness of each 100ppmv tranche up to 1000ppmv, with the total global warming in each of the five diminution assessments.
The table below shows the likely range of warming arising from these divergent (sceptical and IPCC) views, (without feedbacks, which are questionably either negative or positive: but probably not massively positive as assumed by CAGW alarmists), that would be averted with an increase of CO2 for the full increase from 400 ppmv to 1000 ppmv.
The results above for countries and country groups show a range for whichever scenario of only a matter of a few thousandths to a few hundredths of a degree Centigrade.
However it is extremely unlikely that the developing world is going to succumb to non-development of their economies on the grounds of reducing CO2 emissions. So it is very likely that the developing world’s CO2 emissions are going to escalate whatever is done by developed nations.
These figures show that whatever the developed world does in terms of decreasing CO2 emissions the outcome is likely to be either immaterial or more likely even beneficial. The table below assumes that the amount of CO2 released by each of the world’s nations or nation is reduced universally by some 20%: this is a radical reduction level but just about conceivable.
These extreme, economically destructive and immensely costly efforts by participating western nations to reduce temperature by de-carbonization should be seen in context:
§ the changing global temperature patterns, the current standstill and likely impending cooling.
§ the rapidly growing CO2 emissions from the bulk of the world’s most populous nations as they continue their development.
§ the diminishing impact of any extra CO2 emissions on any temperature increase.
§ normal daily temperature variations at any a single location range from 10°C to 20°C.
§ normal annual variations value can be as much as 40°C to 50°C.
§ that participating Europe as a whole only accounts for ~11% of world CO2 emissions.
§ that the UK itself is now only about ~1.5% of world CO2 emissions.
As the margin of error for temperature measurements is about 1.0°C, the miniscule temperature effects shown above arise from the extreme economic efforts of those participating nations attempting to control their CO2 emissions. Thus the outcomes in terms of controlling temperature can only ever be marginal, immeasurable and thus irrelevant.
The committed Nations by their actions alone, whatever the costs they incurred to themselves, might only ever effect virtually undetectable reductions of World temperature. So it is clear that all the minor but extremely expensive attempts by the few convinced Western nations at the limitation of their own CO2 emissions will be inconsequential and futile[6].
Professor Judith Curry’s Congressional testimony 14/1/2014[7]:
“Motivated by the precautionary principle to avoid dangerous anthropogenic climate change, attempts to modify the climate through reducing CO2 emissions may turn out to be futile. The stagnation in greenhouse warming observed over the past 15+ years demonstrates that CO2 is not a control knob on climate variability on decadal time scales.”
Professor Richard Lindzen UK parliament committee testimony 28/1/2014 on IPCC AR5[8]:
“Whatever the UK decides to do will have no impact on your climate, but will have a profound impact on your economy. (You are) Trying to solve a problem that may not be a problem by taking actions that you know will hurt your economy.”
and paraphrased “doing nothing for fifty years is a much better option than any active political measures to control climate.”
As global temperatures have already been showing stagnation or cooling[9] over the last seventeen years or more, the world should fear the real and detrimental effects of global cooling[10] rather than being hysterical about limited, beneficial or now non-existent warming[11].
References:
[1] http://www.grida.no/publications/other/ipcc%5Ftar/?src=/climate/ipcc_tar/wg1/222.htm
[2] http://www.powerlineblog.com/archives/2014/05/why-global-warming-alarmism-isnt-science-2.php
[3] http://www.copenhagenconsensus.com/sites/default/files/ccctolpaper.pdf
[4] http://www.geocraft.com/WVFossils/greenhouse_data.html
[5] http://www.spectator.co.uk/features/9057151/carry-on-warming/
[6] http://hockeyschtick.blogspot.fr/2013/11/lomborg-spain-wastes-hundreds-of.html
[7] http://www.epw.senate.gov/public/index.cfm?FuseAction=Files.View&FileStore_id=07472bb4-3eeb-42da-a49d-964165860275
[8] http://judithcurry.com/2014/01/28/uk-parliamentary-hearing-on-the-ipcc/
[9] http://www.spectator.co.uk/melaniephillips/3436241/the-inescapable-apocalypse-has-been-seriously-underestimated.thtml
[10] http://www.iceagenow.com/Triple_Crown_of_global_cooling.htm
[11] http://notrickszone.com/2010/12/28/global-cooling-consensus-is-heating-up-cooling-over-the-next-1-to-3-decades/
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
“””””…..The entire debate should have ended with “CO2 is logarithmic”. It has remained alive by an elaborate shell game by the IPCC. They present facts which are utterly true, and completely irrelevant. When we apply THEIR math and THEIR sensitivity and THEIR calculations to the here and NOW, their argument goes “poof” and disappears in a puff of logic……”””””
If the CO2 effect (on surface / lower tropo temperature) is logarithmic, the going from 280 ppm to 560 ppm should give the same temperature rise, as going from 1 ppm CO2 to 2 ppm; or for that matter, from one molecule of CO2 per cubic meter, to 2 molecules of CO2 per cubic meter.
CO2 temperature response IS NOT logarithmic.
Maybe it id “non-linear” ; but it ain’t logarithmic.
The logarithm function is very specific.
There isn’t any CO2 / Temperature data, that differs in any statistical sense, from linear. They often even go in the opposite direction. What kind of logarithmic function is that.
Any data there is can just as well be fitted to the function: y = exp(-1/x^2). And moreover you can use either y or x for the temperature; or for the CO2 if you like.
That function goes from 0,0 to 1,1/e, and all points beyond (both ends) but at x = y = 0, dy/dx =0
And so does all the higher derivatives. So how the hell, does it ever get to 1/e if it can never get started ??
So don’t hang you hat on any supposed logarithmic dependency on CO2; there isn’t any.
[+emphasis]
Curt, to no avail in this and other WUWT posts, others (and I) have tried to show the emphasized concept to Kristian.
I do wish you all the best in trying to get him to understand.
🙂
Matthew R Marler says: August 10, 2014 at 9:30 pm
“Thanks to Ed Hoskins for a good essay.”
I asked above if anyone could explain the arithmetic expressed at many points in % – eg
“CO2 at 400pmmv is already committed and immutable. So CO2 has already reached about ~87+% of its potential warming effect in the atmosphere.”
That seems to me to be central to the essay, and also nonsense. Can you help?
richard verney says:
August 10, 2014 at 10:05 pm
My eyeball needs a power source too, but that doesn’t mean a photon doesn’t do work on the retina. It just has to be darker than the source.
“””””…..agfosterjr says:
August 10, 2014 at 7:38 pm
At room T my T gun can measure and compare fridge and freezer T. How can it do that if radiation can’t be transmitted from a cold to a hot place? –AGF …..”””””
Radiation can go anywhere.it darn well pleases; because radiation is NOT “heat”.
So splain me how the 2.7k BB microwave background radiation, can even be detected on earth if it can’t come here, because we are much hotter that 2.7 K.
Heat is (chaotic) mechanical kinetic energy. It IS NOT electro-magnetic radiation, which is a propagating field .
george e. smith says: August 10, 2014 at 10:08 pm
“CO2 temperature response IS NOT logarithmic.”
This goes back at least to Arrhenius. Or as he puts it
“Thus if the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression. “
@F. Ross: you have missed the key issue which is that heat transfer is not the difference in the ‘two flows’. There is only one ‘flow’ set by the integral over all wavelengths of Poynting Vectors of waves whose amplitude is the difference of the warmer and cooler amplitudes.
In simple terms, it takes two to tango. I’m glad that there is a critical mass of professionals writing on this thread who insist on this crucial bit of thinking. Climate Alchemists fixated on ‘back radiation’ have nowhere to hide because the Climate Models are classic groupthink fail.
In simple terms the heat generation rate in the atmosphere is 238.5 SW thermalisation + 333 ‘back radiation’ – 238.5 supposedly from applying Kirchhoff’s Law to the -18 deg C emitter at ToA.
The sum is 333 W/m^2, 140% of the real heating rate. That 40% is imaginary. The reason is that there is no single -18 deg C emitter. -18 deg C is the flux weighted mean emission temperature of IR sources at altitudes ranging from 0 to ~20 km. It is a virtual emitter with no physical existence.
It’s time we shut down departments which teach the false ‘back radiation’ concept, our era’s equivalent of ‘Phlogiston Theory’.
Excellent example! Wish I’d thought of it.
I didn’t see any mention of the “optical depth” of the atmosphere in the blog or comments. One can’t understand why increasing CO2 will increase warming without considering optical depth.
You still get an increase in greenhouse warming even if the atmosphere were saturated, because it’s the absorption in the thin upper atmosphere (which is unsaturated) that counts. It’s not even true that the atmosphere is actually saturated with respect to absorption by CO2.
Water vapor doesn’t overwhelm the effects of CO2 because there’s little water vapor in the high, cold regions from which infrared escapes, and at the low pressures there water vapor absorption is like a leaky sieve, which would let a lot more radiation through were it not for CO2.
@F. Ross: you detect the cosmic microwave background with a radio telescope. 2.72548 deg. K is equivalent to a peak 160.2 GHz radio wave.
davidmhoffer says:
August 10, 2014 at 7:20 pm
////////////////////
The oceans have thermal inertia, the atmosphere has thermal inertia, that is why the night time temps do not drop to say -155degC as seen on the moon (even the moon with its lengthy nights, its surface does not get down to 3K).
The difference between day and night temps, is essentially governed by the thermal inertia of the atmosphere, and where I am, even though it was clear skies tonight (thus completely open to the 3K of space) the night temp did not drop below about 24degC. If it had been a cloudy night, it would not have been any warmer (significantly warmer).
GHGs may alter the thermal inertia of the atmosphere. GHGs such as CO2 may delay surface radiated LWIR from going directly to space, bouncing it around a bit, or even a lot, thereby delaying the cooling process, but I am sceptical that they add anything of substance to the night time low.
On the other hand, when it is very humid and the atmosphere itself is carrying a lot more energy, night time temps can be kept up. In these conditions there is both more thermal lag and more energy in the atmosphere such that night time temps are kept up. In those conditions, where I am, it is possible for the nightime temps to drop not below about 28 or even possible about 30degC.
PS. I am only about 1000 metres from the sea, and the difference between high humidity and low humidity is stark. .
PPS. If the pause continues for an extended time (and even some warmists are suggesting that there may be no resumption of warming before 2030), I expect to see, not simply a re-assessment of the positive/negative feeback forcings that may amplify or attentuate the ghe of CO2, but also a re-evaluation of the basic physics underpinning the AGW theory, and one area that will get attention is the proper assessment of the GHE and wheher it truly is about 33degC, or whther it is less than that>
DWLWIR varies but is something in the order of 340 W/m-2, roughly. This value occurs at night as well. So if I walk out of my house at night into this downwelling infrared, it would seem like I should be able to feel it on my skin, since it is about the same intensity as regular sunlight at about 9 to 10 in the morning. Hmmm. I don’t feel a thing.
Paul 767:
At August 10, 2014 at 3:49 pm you write
Oh! So, Irenaeus,the 2nd century by Bishop of Lyon, was a “leftist”. And so was St. Augustine. And so was …
And you go on from that false premise about “leftists” to ascribe to them attributes which are not general to people of the left and are not unique to people of the left.
In addition to being way off-topic, your troll comments are plain daft, but they are typical of ultra-right untruths as adopted, perfected and used by propagandists for the German ultra- right in the 1930s.
Richard
Nick Stokes: I asked above if anyone could explain the arithmetic expressed at many points in % – eg
“CO2 at 400pmmv is already committed and immutable. So CO2 has already reached about ~87+% of its potential warming effect in the atmosphere.”
That seems to me to be central to the essay, and also nonsense. Can you help?
That is an interesting question and I am glad that you have come back to it. I think that it is sloppy writing, like referring to the “equilibrium” temperature of a high dimensional dissipative system that never has an equilibrium. I think there is an implicit upper bound of about 3,200 ppm (never stated, hence implicit), and the claim is that we are about 87% of the way to the effect of that implicit likely upper bound on CO2. Starting at 400ppm (an idea I work with frequently), the next doubling is to 800 (adding 1 C, give or take); the next doubling is to 1600 (adding another 1 C, give or take), and the next doubling is to the extremely high and unreachable 3200 (adding another 1C, or whatever you prefer.) Thus, 3200, or whatever, is not an asymptotic value but a reasonably realistic upper bound, probably not a least upper bound. Whatever the unit increase per doubling is, we are about 90% as far as we are going to get if the atmospheric CO2 continues to double for the next 450 years at its present rate, since only 3C (or 3 times your favorite value) will be added in 450 years.
Analogously, if I say that the scientific publications and in-house techreports are “uncountable”, I do not mean the mathematical uncountable, only that there is not likely to be sufficient manpower invested in counting them ever to come up with more than upper and lower bounds.
The asserted doubling of CO2 concentration is hypothesized to result in an increase of 3.8W/m^2 downwelling radiation, and the hypothesized increase in temperature comes from considering only the equilibrium radiative effects on a planet with a uniform surface and uniform temperature. If you consider the effects of that increased radiative energy impinging on the non-dry regions of the Earth surface, and that it takes about 660 more energy to vaporize a kilogram of water than to raise its temperature 1C, then I think it becomes clear that ignoring the evaporation effects in the non-equilibrium system leads to a serious overestimation of how much warming can be produced by a doubling of CO2. The cloud responses, not agreed upon in the peer-reviewed literature, make the idea of a constant sensitivity to doubling of CO2 a dubious concept anyway.
@richard verney: 33 K GHE is bad physics from 1981_Hansen_etal.pdf. That paper, which should never have passed peer review, claimed with no evidence that OLR comes from a single 5 to 6 km upper atmosphere IR emitter at -18 deg C in radiative equilibrium with Space.
-18 deg. C is the flux-weighted virtual temperature of a virtual emitter. Real GHE is obtained by calculating no cloud or ice albedo, 341 W/m^2, mean surface temperature and subtracting that 4 to 5 deg C from present ~15 deg C, ~ 11 K. Lindzen has come up with about 16 K GHE.
Hansen et al claimed GHE = lapse rate warming from 4 or 5 km to the surface. However, this temperature change arises purely from gravity. The 40% extra energy which comes from assuming atmospheric emittance is a real energy flux is supposedly used to increase latent and sensible heat as surface temperature rises, thereby moving upwards the -18 deg C virtual emitter. However, this assumes there are no atmospheric mechanisms bypassing the ‘CO2 – bite’ in OLR.
The real climate system keeps SW thermalised = OLR whilst minimising diurnal variation of surface temperature. The atmospheric processes mean near zero surface temperature change from well-mixed GHGs concentration change. GHE variation is solely from cloud and ice albedo change.
Scott says:
(August 10, 2014 at 5:20 pm)
“”Re The logarithmic response means that we need to add twice as much CO2 again to create the same amount of warming we created with the initial increase…..”
I think you mean 10 times the amount based on a Log base 10 effect to get twice the temp.”
_____________________
Hi Scott.
I mean in terms of doubling concentrations of CO2. If CO2 doubles from 280 to 560ppm and this causes, say, 2 deg C warming, then in order to get a further 2 deg C warming you’d need to double from 560 to 1120ppm.
The point is that just because the impact on temperature of increasing CO2 concentrations is logarithmic, this doesn’t mean that further increases in CO2 won’t cause further. They will.
James Abbott:
At August 10, 2014 at 5:19 pm you ask
Nobody suggested that the sea level rise should be greeted with anything; you introduced that red-herring.
And the economic cost of defending “major coastal cities from such a sea level rise” would be zero because any needed alterations to sea defences would be obtained as part of the normal maintenance of sea defences.
Richard
Nick Stokes: A parabolic reflector focusses a parallel beam.
Yes, and if you put an IR source at the focal point the mirror will create a parallel beam of IR.
george e. smith: Heat is (chaotic) mechanical kinetic energy. It IS NOT electro-magnetic radiation, which is a propagating field .
The concept here is that the energy in the electro-magnetic radiation can be converted to kinetic energy (and vice versa) through interaction. Two examples: radiation from the sun is absorbed by the electrons in orbits around the nuclei of diverse atoms, raising the energy levels of the orbits of the electrons, and through inter-atomic collisions the energy is transferred into the kinetic energy of the surrounding atoms; electrons in energetic “orbits” can decay into lower energy orbits, and thereby give off energy in the form of electromagnetic radiation.
Attempts by people to deny these basic concepts are astonishing. Kristian has argued that when the electrons transition from higher energy level orbits to lower energy level orbits and generate IR that way, the energy of the electrons disappears (or at least goes somewhere other than the radiation that he has not told us about.) Other people have argued that the radiant energy from CO2 molecules in the lower troposphere can’t go toward the surface because the CO2 molecules somehow know that the surface has a higher mean kinetic energy than the surrounding air; without explaining to us how the radiant energy emerging from the CO2 molecules knows that.
IF CO2 concentration is a cause of temperature, not an effect. There is nothing to support this.
“The recent IPCC report now admits that currently increasing CO2 levels are probably only ~50% man-made.”
Link with direct quotation (or chapter and page from AR5 WG1) would be very much appreciated if someone could provide this. Thanks.
F. Ross says:
August 10, 2014 at 10:27 pm
///////////////////////
I have never seen anyone argue that DWLWIR does not exist at all, ie., it is not even a signal capable of measurement. I do not consider that an issue raised by sceptics, but rather, one or more of the following:
The issue is what does DWLWIR actually do? Does the 2.7K DWLWIR from space help maintain the surface of planet Earth at its about 288K temperature? Does the 255K DWLWIR from about 17,000ft help maintain the surface of planet Earth at 288K? Etc.
Does increasing the amount of CO2 in the atmosphere actually increase DWLWIR? See: http://wattsupwiththat.com/2014/08/05/bombshell-study-shows-greenhouse-gas-induced-warming-dropped-for-the-past-14-years/ That was just one study, from which it would be wrong to seek to extrapolate a global wide effect, but the study does raise an interesting point upon which further research would be useful.
Is the radiative effect of CO2, at around today’s level of circa 280 to 400ppm, completely dwarfed by the water cycle? See the comment of E.M.Smith at August 10, 2014 at 1:03 pm.
What is the correct assessment of the GHE on planet Earth? See: AlecM at August 10, 2014 at 8:36 am. What is the evidence of a GHE on any planet/body in the Solar System?
What are the feedbacks, their correct assessment and are these positive or negative?
The fact that it appears that CO2 lags temperature change, on every time scale, and the 18 year pause seem to suggest that CO2, at a level above about 200ppm, may do little.
Whilst I understand that most people have a desire to argue from within the ‘consensus’ science, no doubt because they consider that they will be taken more seriously, or at any rate, not simply ridiculed, but it is worth rembering that history shows that consensus science is usually wrong.
Any objective observer would recognise that the AGW hypothesis has many problems with it. To what extent these are fundamental is yet to be revealed, but it may well be the case that in the next 20 or so years, scientists will have a very different take on it going beyond the climate sensitivity issue.
Cost to Europe 165bn a year for rest of this century. Wouldn’t be surprised, but where does this figure come from?
Matthew R Marler says: August 11, 2014 at 12:06 am
“I think there is an implicit upper bound of about 3,200 ppm (never stated, hence implicit), and the claim is that we are about 87% of the way to the effect of that implicit likely upper bound on CO2.”
Well, thanks, that sounds dodgy, but still doesn’t elucidate the arithmetic. What is the numerator, and what the denominator, in the 87%?
Richard
I made the observation way above that I thought 280ppm was the probable limit for an effect
http://wattsupwiththat.com/2014/08/10/the-diminishing-influence-of-increasing-carbon-dioxide-on-temperature/#comment-1706343
Can I get you to raise your estimate to that from 200ppm then we will have a 100% consensus on those that expressed an opinion? We might get it tweeted by Obama….
tonyb