Bishop Hill A problem with the AGW hypothesis
Jun 21, 2012 Climate: MWP Climate: other A paper published in Nature last week claims that 12 million years ago the sensitivity of the Earth to carbon dioxide was profoundly different, with very high temperatures maintained despite very low levels of the bogeyman gas.
Deep-time palaeoclimate studies are vitally important for developing a complete understanding of climate responses to changes in the atmospheric carbon dioxide concentration (that is, the atmospheric partial pressure of CO2, pco2)1. Although past studies have explored these responses during portions of the Cenozoic era (the most recent 65.5 million years (Myr) of Earth history), comparatively little is known about the climate of the late Miocene (~12–5 Myr ago), an interval with pco2 values of only 200–350 parts per million by volume but nearly ice-free conditions in the Northern Hemisphere2, 3 and warmer-than-modern temperatures on the continents4. Here we present quantitative geochemical sea surface temperature estimates from the Miocene mid-latitude North Pacific Ocean, and show that oceanic warmth persisted throughout the interval of low pco2 ~12–5 Myr ago. We also present new stable isotope measurements from the western equatorial Pacific that, in conjunction with previously published data5, 6, 7, 8, 9, 10, reveal a long-term trend of thermocline shoaling in the equatorial Pacific since ~13 Myr ago. We propose that a relatively deep global thermocline, reductions in low-latitude gradients in sea surface temperature, and cloud and water vapour feedbacks may help to explain the warmth of the late Miocene. Additional shoaling of the thermocline after 5 Myr ago probably explains the stronger coupling between pco2, sea surface temperatures and climate that is characteristic of the more recent Pliocene and Pleistocene epochs11, 12.
If, as this report on the paper suggests, the Miocene was "a time of nearly ice-free conditions in the Northern Hemisphere and warmer-than-modern conditions across the continents", shouldn't all of those positive feedbacks have kicked in and fried the planet?
Reader Comments (17)
No you are missing the point. Positive feedbacks only become real if there is an incandecent bulb within 50 years. Outside of that time range positive feedbacks are just imaginary waiting to appear from the alternate reality upon the invention of the SUV
Positive feedbacks are an artefact of incorrect IR physics in the models.
These assume 100% direct IR thermalisation. However, Nahle's recent experiment shows that when you reduce the wall thickness of the 'PET bottle' by a factor of ~12 by replacing it with a Mylar balloon, there is no detectable warming: www.slayingtheskydragon.com/images/PDFs/BERTHOLD-KLEIN.pdf
Climate science was warned of its incorrect IR assumption in 1993 by Will Happer.
Partial pressure is expressed in parts per million? This oxfordshire housewife was expecting pressure untis, who knew?
But you must realise there is the same convertibility between partial pressure and concentration in ideal gases as there is between the standard housewife and the Ideal home......
Your Grace,
Did you check with the authors of the paper before posting this, just to make sure you have indeed got the right end of the stick?
If Huffman and Nicholov & Zeller are right then the partial pressure of CO2 wouldn't matter - just the total atmospheric pressure, regardless of chemical composition. Does anybody know if these techniques can estimate total pressure?
Tilting
No, I'm just relaying the paper to readers. Is there's something wrong in what I've said?
This is science, not exegesis. It is enough to consider whether an interpretation is right or wrong and the original authors' opinions , valuable as they may be, are not essential to understanding their work.
Only problem with this new paper is that it fails to acknowledge that not everybody agrees that late Miocene CO2 levels were low. For example, Pagani et al., Science 6 August 1999: Vol. 285 no. 5429 pp. 876-879
The global expansion of C4 grasslands in the late Miocene has been attributed to a large-scale decrease in atmospheric carbon dioxide (CO2) concentrations. This triggering mechanism is controversial, in part because of a lack of direct evidence for change in the partial pressure of CO2(pCO2) and because other factors are also important determinants in controlling plant-type distributions. Alkenone-based pCO2 estimates for the late Miocene indicate that pCO2 increased from 14 to 9 million years ago and stabilized at preindustrial values by 9 million years ago. The estimates presented here provide no evidence for major changes in pCO2 during the late Miocene. Thus, C4 plant expansion was likely driven by additional factors, possibly a tectonically related episode of enhanced low-latitude aridity or changes in seasonal precipitation patterns on a global scale (or both).
Also see Pearson and Palmer, Atmospheric carbon dioxide concentrations over the past 60 million years
Since the early Miocene (about 24 Myr ago), atmospheric CO2 concentrations appear to have remained below 500 p.p.m. and were more stable than before, although transient intervals of CO2 reduction may have occurred during periods of rapid cooling approximately 15 and 3 Myr ago.
Both these papers are extensively cited (771 citations for Pearson and Palmer) so it is difficult to imagine the authors of the new paper were unaware of them.
No, your highness, positive feedbacks do not "fry the planet". They just warm it up faster than without them. You are perhaps confusing "positive feedbacks" with "positive feedbacks above 1.0", which would mean a "runaway greenhouse effect". The difference is subtle but very important.
Present issue is if whether the warming we will have is sufficiently high so that it will pretty much change too many things on our ecossystem for us to cope with. And by "cope with", one can mean many things. To me, I think, the question is if our economies and general happiness (which may include our fondness for this planet we inhabit) will be or not severely hurt or not.
Luis; there is probably no net CO2-AGW. so positive or negative feedback means nothing.
The key argument is whether it's because the experimental absorptivity/emissivity of CO2 in air levels off at ~200 ppm for an infinite physical optical path. Hottell's and Leckner's work is explained by the IR phenomenon of 'self-absorption' reducing absorptivity facing the IR source, hence no possible CO2-AGW.
The alternative argument is that the IR energy, which has been exaggerated five-fold anyway by the heat transfer mistakes in the models, is pseudo-scattered to be thermalised at clouds and that accelerates the water cycle as [CO2] increases, the explanation of Miskolczi.
So, spoilt for choice I'm afraid, none of it IPCC-approved, but who cares?
I don't understand the grammar of this sentence. What do you mean by "no net"? The CO2 effect is real, it's not an "illusion". You might want to discuss how the general atmosphere reacts to it, if it amplifies its effect, if it dampens it, or if it "changes it" to another thing altogether or all of the above (depending on the situations), etc. But the effect itself is simple, and I'd cross-check your sources on this matter. Urgently.
Alex,
"Only problem with this new paper is that it fails to acknowledge that not everybody agrees that late Miocene CO2 levels were low. "
Is it necessary that everyone agree? Who is "everyone"?
Hi Luis; GHGs absorb IR energy but there is no experimental proof of direct thermalisation by collision, as claimed in climate science. Firstly, there is no mechanism for this to happen, quantum exclusion means it has to be indirect via GHG-GHG collisions. Secondly, the Tyndall and 'PET bottle' experiments have been disproved by Nahle using a Mylar balloon, detecting no warming.
This has to be replicated but the probable explanation is from classical statistical thermodynamics. Climate science fails to understand the Principle of Indistinguishability, molecules have no memory. A photon emitted at the same time as the original photon is absorbed, thermally transfers that energy elsewhere, so no change in local temperature.
This occurs throughout the atmosphere with the energy spilling over into heterogeneous interfaces, indirect thermalisation. or to space. Hence the warming in the PET bottle is conversion to heat in the PET, not the gas, plus constrained pressurisation. I could be wrong but no-one has so far shown why apart from trotting out assumptions unproved by experiment. Single molecule data do not count.
Your Grace,
Relaying such papers to your readers is a valuable service for which we are grateful - thank you.
But in addition to simply relaying, you provide comment that this is 'a problem for the AGW hypothesis' - indeed this seems to be the very reason you chose to share the paper, although I am happy to be corrected on this point if necessary.
Let's say your comments are true and the paper really does make a mess of AGW theory by implying that the planet would fry. This is a fundamental enough implication that the paper would mostly likely be written in a very different way to make this more explicit. It would also be picked up much more than it has been by other sources (yes, I know non-consensus studies generally get less air time, but the GWPF and Daily Mail would still be delighted to take up the cause).
Given all this hasn't happened, maybe the paper doesn't imply what you suggest? A very simple way to find out would be for you to check with the authors before blog posting. That way we could all have a more informed discussion...
AR4 already indicates that higher temperatures have existed in periods of lower CO2 levels as recently as 100,000 years ago in the last interglacial. Their graphs in the paleoclimate section show temperatures apprx 3degC higher than today at CO2 levels of 250 ppm. Some recent papers suggest the difference might be as much as 6degC.
tilting
Bish qualifies his ‘frying’ remark with: “If, as this report on the paper suggests..”.
He’s being careful, as usual.