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Goodbye to all that

Filed under: — group @ 1 December 2007

This post announces my (William Connolley’s) departure from RealClimate, and indeed from the professional climate field in general, in favour of the wide world of Cambridge software engineering. I’ve enjoyed my time with (Real)Climate, but now its time to move on.

Normally the career change of one minor scientist would be of little interest to the outside world, and perhaps this one will be too, but the climate arena does get rather highly charged. So perhaps a few words of explanation are in order.

This doesn’t represent any disenchantment on my part with the state of the science, or with IPCC, or with RealClimate – all of which continue to have my respect. I’m sure that RealClimate will continue to deserve its high reputation as a source of accessible explanation and comment on important climate issues. It’s more a reverse of that – in some senses, much of the main areas of climate science have now become much clearer than when I began to be interested; the obstacles to progress are now very obviously political not scientific.

I expect to continue my (now amateur) interest in climate; my pet blog will remain at least for a while – feel free to join me there.


130 Responses to “Goodbye to all that”

  1. 51
    Lynn Vincentnathan says:

    RE the theme here that the major part of the CC science has been done (more than enough to support vigorous action to mitigate CC), and the work now is on the details…and brushing away those pesky denialist arguments and theories…

    Here’s a recent detail that surprised me: harm to agriculture from GW may have been underestimated because studies failed “to account for seasonal extremes of heat, drought or rain, multiplier effects of spreading diseases or weeds, and other ecological upsets” (see http://www.climateark.org/shared/reader/welcome.aspx?linkid=89060 )

    It surprised me because I’ve been arguing for over 15 years it’s these extremes we have to keep our eyes on, not the averages — as in an extreme heat wave over several days can kill almost an entire crop, while the average weather conditions over the entire growing season may even look ideal. Or a deluge over a few days may do a lot of damage, while the same amount of rainfall spread more evenly over a few months may help crop production.

    I studied some ecological anthropology decades ago, and we were taught that when looking at the carrying capacity of, say, a pastoral tribe’s land, we had to look at the carrying capacity during that once in a hundred years drought, not the carrying capacity of the average year or the most productive year.

  2. 52
    Steve Reynolds says:

    I also want to thank William for his work.

    BTW, there is an interesting sea ice bet on Williams’s blog:
    http://scienceblogs.com/stoat/2007/12/betting_on_sea_ice_following_t.php

    I’m curious if anyone here thinks arctic sea ice will be below 10% by 2020.

  3. 53
    Geoff Wexler says:

    Best wishes. I hope you will take part in the politics in your spare time and perhaps appear in the media sometimes. I agree with George Marshall that many people don’t seriously really believe scientists although they may pay lip service to what they are told.

  4. 54
    Jon says:

    Best of luck!

    I’ll continue to look forward to your posts on Stoat. It was nice to see your continued ability to offer some alternative opinions to the more political/ideological aspects of the discussion while maintaining confidence in what I suppose could be called the “mainstream” of the science itself.

  5. 55
    Ike Solem says:

    Best of luck! A 90% reduction in fossil fuel use is indeed technically and scientifically possible, and so is halting the destruction of the world’s forests and other carbon stores. The lights will stay on (but the cars will all be smaller). Getting from here to there is the problem – but you’ve certainly contributed to the process. Congratulations. (Maybe you can help make some more positive contributions in the computer world” as well!)

  6. 56
    joel says:

    http://wattsupwiththat.files.wordpress.com/2007/11/ca_climate_variability_ladochy.pdf

    Is this paper OK?

    If so, this paper really reopens the UHI effect question. I would welcome comments on it.

    [Response: What UHI question? The issue is not whether it exists, but whether it contaminates the global temperature reconstructions despite, for instance, the avoidance of urban trends sites in GISTEMP. This paper doesn't address this. - gavin]

  7. 57
    Joseph O'Sullivan says:

    Its sad to see you leave RC, I hope you keep posting on stoat. At least you’re not becoming a fashionista i.e. comment #45 ;)

    I did get an undergrad degree in marine biology, but the career choices in a very crowded field and my time as a lab tech persuaded me to take a different career path. I never got to the point where I was a scientist, but I understand the urge to find a new path.

  8. 58
    Eachran says:

    All those years ago, it seems, I sent you an e-mail to ask where I should start to understand climate science better. I tracked you down after reading some of your stuff on the exchanges on the wikipedia pages. I quite liked your style : you seemed to be knowledgable honest and dogged.

    You were kind enough to put me on the right path and from there, which included IPCC, to RC and to a large number of links provided by the posters here.

    I now feel very comfortable with the science and I can hold my own in conversations with the sceptics more often than not.

    It wouldnt have happened without you, so thanks and good luck for the future.

  9. 59
    pete best says:

    A report today in the Independent makes some statements about our local star (the Sun) and cycle24 and how in the coming decades there is a strong possibility of a 1.5C temperature drop in earths (it does not say global) temps which would give us more time to deal with CO2 emissions. Apparantly the Sun was very active during the 20th century but far less so now.

    I am presuming that this would not necessarily be a good thing as it if was colder in Europe and the USA then more fuel would be used to keep warm and keep pur industry moving.

  10. 60
    Alan says:

    CS-SE101: “Leading a team of programmers is like hearding cats” – But I can understand why it’s appealing… :)

  11. 61
    Decca says:

    Luft. 0,81Kg/m3 og inneholder 0,038% CO2

    Propan. 1,83Kg/m3 legger seg i bunnen av båtskrog ved lekkasjer og er eksplosjonsfarlig.

    CO2. 1,98Kg/m3 stiger til “himmels” og danner varmeskjold og global oppvarmning.

    Hvor er logikken? En gass som er over dobbet så tung som Luft, stiger i luft, men Propan stiger ikke

  12. 62
    Ray Ladbury says:

    Hi Pete,
    The idea is that we’re due for a decrease in solar activity, leading to lower temperatures. The thing is there’s no model for predicting how much or how long it will last. The longest grand minima last of order 200 years, while the effects of CO2 persist for centuries to millennia. Moreover, historically, given the nearness of peak oil, we are currently deciding on infrastructure for the future. If we opt for coal (the cheapest option) we will manage to restore Earth to a Jurassic atmosphere, completely different from the one we know today. There seem to be some who are confident of our ability to put the carbon back in the ground after we release it. All I can say is that if we have done as poorly with mercury as we have, it doesn’t inspire confidence.

  13. 63
    Martin Vermeer says:

    #61 decca

    Hvor er logikken? En gass som er over dobbelt så tung som Luft, stiger i luft, men Propan stiger ikke

    At snakke Norsk gør ikke logikken betre… ;-)

    So the question asked is, how can CO2 being twice as dense as air, nevertheless go up to the heavens, when also heavy propane leaking inside a boat, stays on the bottom of the hull.

    I think it is simply a matter of the speed of becoming “well mixed”. Inside the boat, the air is standing still. The only process to mix the propane with the air is gas diffusion, which is slow. The CO2 however becomes part of atmospheric circulation. And even then, full mixing takes a little while (months). CO2 released in stagnant air also stays at the bottom and may become a lethal suffocation trap.

  14. 64
    Hank Roberts says:

    > CO2 being twice as dense as air

    According to what source? Why do you consider this reliable information?

    I’m always interested in where people get their beliefs underlying their reasoning. This has fooled some well known people.

    But you can look it up, for example http://www.uigi.com/air.html

    the molecular weight
    -of dry air 28.98
    -of nitrogen 28.01
    -of oxygen 32.00
    -of argon 39.95
    -of carbon dioxide 44.01

  15. 65
    Martin Vermeer says:

    > CO2 being twice as dense as air
    According to what source?

    Good point! I didn’t even see anything wrong with the figures :-)

    (You don’t happen to have propane do you?)

  16. 66
    pete best says:

    Re #62, I sent the article off to realclimate and Gavin informed with with a nice reply (thanks for that btw Gavin) that it was nigh on impossible for the Sun to cause a temperature drop by 2020 of 1.5C so either the journalist got too excited when interviewing the astronomer or the astronomer was exagerating. But it just goes to show the need for RC and I for one am very glad that they are here and that why its a shame that someone is leaving the field to do software development although I am sure that it will be some decent scientific related development and not business related .NET or JAVA.

    As for mitigating CO2, 1000 coal fired power stations are slated to be built globally in the coming 5 years. CCS will not be available by then and it is difficult to retrofit to I have read. As Kyoto will not run its cause until 2012 and has been a failure anyway due to the fact that economic growth is more important that climate security and Bali talks and any decisions will more than likely meet with the same results.

    IF 400 ppmv does turn out to mean a 2.0C rise in global temps then James Hansen has it right. bulldoze all coal fired power stations not fitted with CCS.

  17. 67

    Carbon dioxide doesn’t stay near the ground because Earth’s air is turbulent. Convection mixes it. If it were stratified by layers, we’d all suffocate, since CO2 and Argon would hug the ground.

  18. 68
    Lynn Vincentnathan says:

    RE #65, I did look up propane molecule (3 Cs & many Hs) and totalled the atomic weights yesterday, and I believe it came out about the same as CO2, but I can’t find those webpages again.

    I’m also thinking that those Hs didn’t seem strongly bonded, not nearly as much as O in O2 or CO2. So it really does seem CO2 can persist a lot longer.

    Well folks, that’s the extent of my chemistry knowledge :)

    Thank goodness for William and all the real scientists to do the work and summarize the results for us!

  19. 69
    Hank Roberts says:

    Google propane “molecular weight”
    * Molecular weight : 44.096 g/mol

  20. 70

    I think you’re right Lynn, it is 44 just like carbon dioxide.

    Barton #67: turbulence mostly only makes it go faster. In a stagnant atmosphere, every gas would eventually be distributed exponentially with height, according to its own scale height (inversely proportional to molecular weight). But it would take a lot of time to get there. In the real (turbulently mixed) atmosphere, there is only one scale height (only water vapour is special) related to mean molecular weight.

    The explosiveness of propane is precisely due to its diffusive mixing with air: a pure layer of the gas overlaid by air would burn at the interface, just like a liquid fuel.

  21. 71
    Tom says:

    Propane is a hydrocarbon, C3H8, with an atomic weight of 3×12 + 8 or 44. It does, coincidently have the same atomic weight as CO2 (12 + 2×16).

    Thanks William, and sorry for all the distractions in the emails.

  22. 72
    catman306 says:

    Students of rapidly melting Arctic Ice and the shutdown of the Atlantic currents will want to take a peak at this:
    http://environment.newscientist.com/article/dn13013-ancient-flood-brought-gulf-stream-to-a-halt.html

    [Response: Oh dear. A perfectly good scientific study (appearing in Science Express this week), ruined again by the headline writers. The Gulf stream did not grind to a halt, not even the thermohaline bit. This might be useful background: http://www.giss.nasa.gov/research/briefs/legrande_01/ - gavin]

  23. 73
    Jim Cripwell says:

    Ref 66 Pete writes ” I sent the article off to realclimate and Gavin informed with with a nice reply (thanks for that btw Gavin) that it was nigh on impossible for the Sun to cause a temperature drop by 2020 of 1.5C so either the journalist got too excited when interviewing the astronomer or the astronomer was exagerating.” This statement is absolutely correct, if the table of forcings in the IPCC SPM AR4 WG1 is correct. That is, only TSI affects climate, and is the only extraterrestrial forcing. Proponents af AGW are unwilling to accept the idea that the sun affects climate in ways which we simply do not understand.

    [Response: Why do you persistently invoke such ridiculous straw man arguments? Think about what it would take in terms of radiative forcing to cool the planet 1.5deg in 13 years. Pinatubo remember only managed 0.5 deg C for a couple of months, and so you'd need at minimum a sustained Pinatubo for years - and that is around -3 to -4 W/m2 of forcing - which is more than an order of magnitude larger than anything even the most far out solar enthusiast has suggested. And in a decade! The statement was/is/remains ridiculous - and it has nothing to do with my lack of an open mind. - gavin]

  24. 74

    All —

    Ross McKittrick appears to have just published a study saying urban heat islands account for the surface warming trend — in JGR-Atmospheres!!! How did that happen?

  25. 75
    Jim Eager says:

    Re Jim Cripwell @ 73: “Proponents af AGW are unwilling to accept the idea that the sun affects climate in ways which we simply do not understand.”

    Without compelling evidence that these “ways which we simply do not understand” even exist or how they work, why would they?

    Why would ANYONE accept the idea that UNKNOWN solar forces that “we simply do not understand” are the cause of the current observed warming when the KNOWN physics of greenhouse gasses explain it perfectly well?

    Unless they have already decided that AGW is not happening and are desperately searching for some other–ANY OTHER–explanation for the observed warming, that is.

  26. 76
    Ray Ladbury says:

    Re: 73. Gavin, I think that you have hit the problem squarely–most people have no idea of the actual numbers involved. It is easy for them to think that somehow we’ll get a big cooling from solar fluctuations because 1)they don’t understand how much TSI fluctuates, 2)They don’t understand how much this is modulated by clouds and how much that fluctuates (and is uncertain), 3)They don’t understand how much energy would be involved in a 1.5 K temperature change.
    This also makes it possible to suggest that 1)Warming is occurring due to massive outpourings of magma hidden beneath the oceans (yes, I have seen this in the denialosphere), 2)Ocean circulation drives climate change, and so on and so on. What all of these fallacies have in common is that they appeal to ignorance–that there must be something we don’t know or that we must not know what we in fact do know. Science is the activity of gaining knowledge; anti-science is the activity of preserving ignorance.

  27. 77
    Phil. Felton says:

    Re #67
    “Carbon dioxide doesn’t stay near the ground because Earth’s air is turbulent. Convection mixes it. If it were stratified by layers, we’d all suffocate, since CO2 and Argon would hug the ground.”

    Not to mention diffusion (although convection certainly speeds things up).

  28. 78
    Chris C says:

    Indeed, and it must account for glacier melt and ocean temperature rise and TOA radiative imbalance as well. I do think gavin and Ray Pierrehumbert are on to something in the “phenomenlogical sequel” thread- something fishy going on with peer review

  29. 79
    SecularAnimist says:

    Jim Cripwell wrote: “Proponents af AGW are unwilling to accept the idea that the sun affects climate in ways which we simply do not understand.”

    It strikes me that this brief comment perfectly encapsulates an entire line of denialist argument:

    “Proponents of AGW — who can point to a mechanism that we do understand, namely the well-established basic physics of greenhouse gases, the indisputable anthropogenic increase in the atmospheric concentration of these gases, and the empirically observed warming of the Earth that is entirely and sufficiently explained by the increase in greenhouse gases — are unwilling to accept the idea that the warming might be caused by some unknown, unobserved, entirely speculative agency such as [fill in the blank with any of several notions that are not even established to exist, whose effects would not well explain the empirically observed changes if they do exist, and are moreover unnecessary to explain the observed warming which is entirely and sufficiently explained by the anthropogenic increase in GHG concentrations].”

    Why do denialists ask the entire scientific community to throw out well-understood and empirically validated science and turn instead to entirely speculative notions about unknown phenomena that have no empirical basis … and expect to be taken seriously?

  30. 80
    Ray Ladbury says:

    Barton and Chris, Not to worry. Peer review is a threshold. I would imagine that the reviewers merely thought it was not so flawed that it was completely uninteresting, and so acquiesced to publication. I’d be interested in the “date received” and “date published” difference as well, as this might indicate how many cycles the manuscript went through. Now that it has been published, it can be given the reception it deserves (Pull!) and then sink into the obscurity it so richly deserves.

  31. 81
    Jim Cripwell says:

    I hope Gavin will allow this lengthy post in answer to Ref 75 by Jim Eager. So far as I can see the case for AGW rests on two pillars. First, that the characteristics of CO2 explain the correlation between the rise in CO2 concentration, and the recent rise in temperature. This argument has been done to death, and I cannot contribute anything new to it. The second pillar is that there is no other explanation for the recent rise in temperature. I think this is false, but if I put my ideas on CS all I get is “Jim, you are preaching to the choir”. Here on RC, any post like this one is looked at in detail, and if there are any mistakes, they are, quite rightly, exposed, and the logic torn to shreds. That way, I learn.
    I am writing this from memory, so I hope you will forgive any errors in minor details. The case that nothing else can affect climate seems to be based on the table in IPCC SPM AR4 WG1, which details all forcings. There is only one extraterrestrial forcing, TSI, or solar constant. When the text of the report is read, Chapter 2.7, one finds two and a half pages of discussion. Two of these pages are devoted to the solar constant, and conclude, with conviction, that the solar constant is indeed constant, and cannot possibly explain the recent rise in the earth’s temperature. The other half page deals with all other extraterrestrial effects. I find this discussion to be totally inadequate and an example of sloppy science. Merely half a page out of thousands of pages, on this absolutely vital issue. There are relatively few citations, and those that are there seem to fall into two categories. Those that support the idea there are no other extraterrestrial effects exist, and those that oppose the idea, but can be easily disregarded. In this latter category we find Svensmark and Marsh 2000, and 2001. However, Svensmark et al Proc. Roy. Soc A October 2006 is omitted; As is any mention of Rhodes Fairchild. I simply cannot be convinced by this part of AR4 that no other extraterrestrial forcings exist. I am no expert on this issue, but if I can easily find relevant citations that are omitted, it is understandable that I find myself unconvinced. Please note I am not claiming that there are unknown extraterrestrial forcings; merely that the IPCC claim that no such forcings exist is totally inadequate,
    We know that in past history, the earth’s temperature has changed markedly; e.g. LIA and MWP. When one asks what caused these periods, the answer seems to be changes in the solar constant. If true, this really does explain everything. Since the solar constant has not changed in recent times, it cannot explain the recent rise in temperature. But if it changed in the past, it explains everything. Is there any evidence that the solar constant has changed sufficiently to affect the earth’s temperature in past times? When I read how the solar constant is measured, I find that earth based measurements are not sufficiently accurate to do the job.. Changes in the earth’s atmosphere have too much effect. One needs satellite observations to do the job. So it was impossible to measure the solar constant prior to satellite technology with the required accuracy. So we have no measurements of what the solar constant was in past eras. Only the usual computer simulations.
    So we have the usual problems with AGW. There is no experimental data, and no convincing arguments that there are no other extraterrestrial forcings except for TSI. Add to this that on a routine basis satellite and other observations are producing more and more solar effects we knew nothing about. We don’t understand how the solar wind, etc. produces aurora. Our models of how the sun works are in disarray, with none of them accurately forecasting the start of solar cycle 24. Dr Hathaway states that the sun is sending “mixed signals”, which really means that his idea of how the sun works is not right. So I am simply not convinced with the IPCC claim that there are no other extraterrestrial forcings except for TSI. Until there is solid scientific information as to what caused the earth’s temperature to vary in past history, and an adequate

  32. 82
    George Robinson says:

    Pete Best, whos this guy James Hansen, who has got it right, got what right??

  33. 83
    Nick Gotts says:

    RE #81 (Jim Cripwell) “I hope Gavin will allow this lengthy post in answer to Ref 75 by Jim Eager.”

    But Jim, your subsequent long post does not even attempt to answer the points made by Jim Eager.

  34. 84
    Hank Roberts says:

    Models underestimating the problem?

    Elements; June 2007; v. 3; no. 3; p. 171-178; DOI: 10.2113/gselements.3.3.171 © 2007 Mineralogical Society of America
    Confronting the Climate-Energy Challenge
    Daniel P. Schrag, Harvard University

    … A brief review of the history of Earth’s climate puts the next hundred years in its natural context, suggesting that most predictions based on climate models may be underestimating the problem. Reducing risks of future climate change requires changes in existing energy systems.

  35. 85
    SecularAnimist says:

    Jim Cripwell wrote: “The case that nothing else can affect climate …”

    There is no “case that nothing else can affect climate” nor does anyone contend that “nothing else can affect climate”. Why do you keep bringing up this strawman?

    The well-understood physics of atmospheric CO2 and other greenhouse gases, and the indisputable empirically observed anthropogenic increase in atmospheric CO2 and other greenhouse gases, are sufficient to explain the current, ongoing, empirically observed, rapid warming of the Earth. There are no other known, observed mechanisms to account for it, nor is there any need to invoke other mechanisms since the well-understood, empirically verified anthropogenic GHG mechanism is sufficient to explain it. There is certainly no need to invoke the various speculative, unobserved “something elses” that you keep handwaving at to explain it.

    You are asking the entire community of climate scientists — hundreds of scientists who have studied this issue for decades — to throw out well-understood, empirically validated and very successful science in favor of hypothetical, speculative, unknown “something elses” … which, moreover, you yourself say you are “not claiming” even exist although you keep talking about them.

    It is remarkable that you receive polite, patient and informative responses to this sort of thing from the climate scientists who post here.

    Jim Cripwell wrote: “So we have the usual problems with AGW. There is no experimental data …”

    That is false no matter how many times you repeat it.

  36. 86
    Majorajam says:

    Jim C,

    Let me see if I have this straight. On the one hand you have a known, experimentally demonstrable radiative forcing increasing in measurable quantities commiserate with the temperature record, and on the other you have mystical, unobserved, unexplained and unidentifiable cosmic forces, and you’re undone because the mainstream scientific community doesn’t assign each causal explanation the same credibility? One wonders how you get out of bed in the morning, what with all we don’t know about potential consequences.

  37. 87
    Nigel Williams says:

    Jim Cripwell – You don’t by any chance drive a Prius do you? How big is your footprint? What social and global outcome are you striving for with your proselytising?

    George 82. Please Google Dr James Hansen to check his creds;
    Then:
    http://www.columbia.edu/~jeh1/
    Then:
    Go quite for a few weeks while you read and digest.
    Then:
    Come back soon y’hear!

    Pete Best 66, Yes bulldoze the CO2 emitters. Agree but only after they have powered the production and distribution of five square metres of photovoltaics per person on earth; only after they have run the motors at the cement plant to build the foundations of the wind turbines; only after we have extracted enough copper for wires and windings stored in the shed on the top of the hill to last us a thousand years; only after they have powered the crushers and conveyor at the mines for the steel to build the new harbours and factories above the 100 metre line..

    We need our present global production capabilities to build our life-boats – only then can we afford to transition to the new way. It’s going to get very messy.

    Any other approach will see a total collapse. No CO2 emitters = No food distribution, no food production, no people, no emissions. Problem solved, mother nature’s way. CO2 trundles up to a peak someplace through 500ppm as we fade away, and Earth swings on thru space unobserved and uncaring. All sorted.

    I cannot see any way ‘economic forces’ are going to solve this – its going to take top-down decision making. The assumption of war-powers on all production. The conversion of plants making TVs to making PVs; making toys to making domestic-scale wind turbines; from golf-links to intensive hands-on efforts – possibly using un-employed professional sports people! ;) to make food grow on unsuitable soils under elevated CO2 and low water regimes; from Christmas lights to solar-powered farm robots – what ever it takes but the entire focus has to change to building Life-Boat Earth or we are gone.

    Only when we have our new world floating safely along side the old can we afford to blow out the smoking stacks of CO2 emitters and jump for our lives!

  38. 88
    Paul Middents says:

    Re: # 81 Who is Rhodes Fairchild?

  39. 89
    Ron R. says:

    William, I remember you from years ago at sci.environment. Along with others: Halpern, Ball, Taylor? Lloyd? etc. You were right in the thick of it and you’ve fought well. But often it’s just hard to keep fighting the same old battles day after day, week after week, month after month, year after year. I myself gave up around 2002. On the other hand the forces of disinformation never seem to tire. Why should they, it’s their job. Anyway, take a break long as you need, you’ve earned it.

  40. 90
    RomanM says:

    Re #75: Jim Eager

    “Without compelling evidence that these “ways which we simply do not understand” even exist or how they work, why would they?

    Why would ANYONE accept the idea that UNKNOWN solar forces that “we simply do not understand” are the cause of the current observed warming when the KNOWN physics of greenhouse gasses explain it perfectly well?”

    In the history of science and philosophy, there have been numerous cases where claims that something was NOT the case turned out to be false due to the lack of understanding the complete mechanism or the consideration of other concurrent factors.

    On July 15, 2007, during a discussion of (the lack of) solar effect on the current temperature in a paper by Lockwood et al., I posted a comment about the substantial changes in global cloud cover over the past several decades.

    http://www.realclimate.org/index.php/archives/2007/12/goodbye-to-all-that/index.php?p=459#comment-37275

    This comment contained a link to a graph on the giss nasa web site:

    http://isccp.giss.nasa.gov/zD2BASICS/B8glbp.anomdevs.jpg

    To my knowledge there was no reply to that post. Since you seem to think that the resultant modulation of solar insolation had no role in the rise in global temperature over this period, perhaps you could point me to an analysis in the climate science literature of how much (if any) of the increase was due to the cloud cover changes.

  41. 91
    Ray Ladbury says:

    Jim Cripwell,
    You claim we have no evidence that the current warming epoch is greenhouse driven. Well, let us review: We have the very deep absorption line at the CO2 absorption band, which interestingly enough actually radiates about at the temperature you’d expect for a greenhouse mechanism. We have the fact that a greenhouse mechanism can explain the qualitative aspects of the current warming–shorter Winters, warmer nights… We have the fact that we know it is operative. We have the fact that it can be explained in terms of known and understood physics. We have multiple, independent lines of evidence that fix CO2 forcing at its current level. Shall I continue? What exactly are you looking for in the way of evidence? If you don’t know what specific piece of evidence would convince you, how can you consider yourself a skeptic and not a denailist?
    In contrast, you posit some unknown forcing that may or may not be operative, that depends on unknown physics and that even if present and significant probably would not affect our estimates of greenhouse gas forcing, since this would require radical explanations of the multiple lines of evidence that fix that quantity. GCMs are not a Chinese menu. It is not a menu where you pick one from column A… Rather, anthropogenic ghg forcings are your vegetables. You can’t leave them on your plate and expect to get dessert.

  42. 92
    Jim Eager says:

    Re Jim Cripwell@ 81: “The second pillar is that there is no other explanation for the recent rise in temperature.”

    Jim, aside from the fact that you’ve left out several other “pillars,” this particular one is not quite correct as you’ve written it.

    To make it correct you would have to change it to read: “No other physical mechanism has yet been shown to be capable of explaining the recent rise in temperature.”

    Elsewhere, you have it backwards when you write that there are “no convincing arguments that there are no other extraterrestrial forcings except for TSI.”

    It’s not up to anyone to offer convincing arguments that there are no other extraterrestrial forcings except for TSI. It is up to those who contend that there ARE other extraterrestrial forcings to not just offer convincing arguments, but to offer convincing EVIDENCE that said extraterrestrial forcings exist and are capable of explaining the recent rise in temperature in whole or in part.

  43. 93
    Jim Cripwell says:

    Ref 91 Ray writes “You claim we have no evidence that the current warming epoch is greenhouse driven” Wrong. I claim there is no EXPERIMENTAL data. There is no hard, measured independently replicated experimental data that shows a connetion between the increased level of CO2 in the atmosphere and the global temperature warming in recent times; i.e. since 1979.

    [Response: Last chance. Describe the experiment that you think will satisfy you. - gavin]

  44. 94
    Jim Eager says:

    Re RomanM @ 90: “In the history of science and philosophy, there have been numerous cases where claims that something was NOT the case turned out to be false due to the lack of understanding the complete mechanism or the consideration of other concurrent factors.”

    Please note that I did not assert that there are NO unknown solar or other extraterrestrial forces that “we simply do not understand.”
    What I asserted is that there is as yet no compelling evidence that these unknown solar or other extraterrestrial forces are capable of explaining the current warming in whole or in part.
    It is up to those advocating these unknown solar or other extraterrestrial forces as climate forcers to provide that evidence for verification and debate.

    Furthermore, the existence of these hypothetical unknown forcings will in no way negate the physics of known greenhouse gasses.

  45. 95

    [Response: Last chance. Describe the experiment that you think will satisfy you. - gavin]

    What about the ongoing experiment? Should be very satisfactory from an evidential viewpoint if nobody stops it :-(

    Last chance indeed.

  46. 96
    Philippe Chantreau says:

    Jim Cripwell: I’ll add that whatever else than GHG forcing is causing the warming would have to also explain the stratospheric and tropospheric changes that have been observed. From what I read, the tropospheric changes correspond exactly to what atmospheric physics says would be expected from GHG warming. So not only would you have to find another plausible source of warming, but you would also have to find one that is going to mimic “side effects” of GHGs.

  47. 97
    Philippe Chantreau says:

    And also: Good Bye, good luck and thanks to William. Just looking at how this thread has drifted, perhaps he won’t miss it all so much…

  48. 98
    RomanM says:

    Jim Eager@94

    “What I asserted is that there is as yet no compelling evidence that these unknown solar or other extraterrestrial forces are capable of explaining the current warming in whole or in part. It is up to those advocating these unknown solar or other extraterrestrial forces as climate forcers to provide that evidence for verification and debate.”

    You are right in saying that the onus is on anyone advocating a specific hypothesis to provide scientific evidence and justification for the truth of that hypothesis. However, in this thread, there seems to be a tendency for some posters saying solar forcing is not active to be very dismissive of a possible effect when it is not clear that they have considered those possibilities in sufficient depth. That was the point I was making in the statement that you quoted. I raised the cloud issue whose possible ramifications on temperatures by varying the amount of solar insolation reaching the earth’s surface, IMO, do not need a “theory”, even though the causes for the formation of those clouds at present do not seem to be well understood, as an example of a reasonable possibility which seems to be a counterpoint to the posters I refer to above.

    “Furthermore, the existence of these hypothetical unknown forcings will in no way negate the physics of known greenhouse gasses.”

    It won’t “negate the physics”, but if such forcings exist, they could certainly affect our knowledge of the quantitative level of the effect of greenhouse gasses. If, as you say in #75, that “… the cause of the current observed warming when the KNOWN physics of greenhouse gasses explain it perfectly well?”, then it would indicate that the amount which now works perfectly well must be an overstatement.

  49. 99
    Jim Cripwell says:

    Gavin writes “Response: Last chance. Describe the experiment that you think will satisfy you. – gavin]” This is the equivalent of the classic “When did you stop beating your wife?” What I was taught when I studied science, was that experimental data and theory were one ball of wax. In true science, experimental data and theory are inseperable. Experimental data by itself is all well and good, but if you dont have a theory or hypothesis to explain it, you dont make progress. By the same token, having a hypothesis or theory with no experimental data to support it, is simply not science; it is at best, pseudoscience. To me the onus is on the proponents of AGW to provide the experimental data to support their hypothesis. How this is done is not my problem. But until it is done, AGW has no scientific basis; it, quite simply, is not science. I am reminded that when I first read about AGW I was amazed to find that the measure of greenhouse effectiveness, namely radiative forcing, can never be measured, and the main greenhouse gas, water, can never be ascribed a value.

    [Response: Thank you. You make it abundantly clear that no amount of evidence will satisfy you. Conversation over. - gavin]

  50. 100
    Ray Ladbury says:

    RomanM–another advocate of the Chinese menu school of Global Climate Modeling? Many have pointed out repeatedly that ghg forcing is constrained by multiple lines of evidence independently of the current warming. It’s not a matter of fitting the forcing to the effect. Rather, it is a matter of fitting the forcings independently of current trends and seeing how well the models do at reproducing them. Since GHGs are among the best known forcings, it is unlikely that they would move much if another mechanism were magically to appear. Rather, if cloud trends were to be responsible for more forcing, aerosols (equally uncertain) would likely change in response.
    This is quite independent of the problems your pet theory would face–like how you can get a cosmogenic forcer to be operative during the day to warm Earth, but not at night, when decreased clouds would tend to cool things.


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