Bishop Hill Shaviv on models and sensitivity
Jan 11, 2012 Climate: Models Richard Betts joined in the conversation about climate models today, making some interesting comments on validation:
As I've mentioned before, the earlier climate models used in the 1970s were used to make estimates of warming over the next 30 years which were fairly close to what happened ... BH asks for tests of the projections made 10 years ago, but the problem is that with internal variability in the system you need longer than that to test the models, unless you specifically initialise the models with the conditions of (say) 2001 using data assimilation techniques, and that kind of thing was not available then, we only started doing it 5 years ago.
So yes, out of sample testing on timescales relevant to GHG rise is an important point but by definition difficult with the latest models!
One minor point is that I had said I would have been more convinced had the story of model versus data in the last ten years been different - I agree with the 30 years figure for falsification. However, more interesting is a point made in a recent post by Nir Shaviv:
From the first IPCC report until the previous IPCC report, climate predictions for future temperature increase where based on a climate sensitivity of 1.5 to 4.5°C per CO2 doubling. This range, in fact, goes back to the 1979 Charney report published by the National Academy of Sciences. That is, after 33 years of climate research and many billions of dollars of research, the possible range of climate sensitivities is virtually the same! In the last (AR4) IPCC report the range was actually slightly narrowed down to 2 to 4.5°C increase per CO2 doubling (without any good reason if you ask me). In any case, this increase of the lower limit will only aggravate the point I make below, which is as follows.
Because the possible range of sensitivities has been virtually the same, it means that the predictions made in the first IPCC report in 1990 should still be valid. That is, according to the writers of all the IPCC reports, the temperature today should be within the range of predictions made 22 years ago. But they are not!
Go and take a look at the graph at Nir's site. This seems a reasonable point to me.
Reader Comments (130)
mdgnn
This is becoming hard to follow. You are now apparently arguing that (in the bigger picture) increased cloud albedo (from the liquid water path) and warming can occur simultaneously. Remembering that Stephens cannot find evidence for a climatologically significant effect for the low cloud LWP there are far too many ifs and buts.
Also, I find your posts barely comprehensible and suspect that this is far from accidental. For the benefit of others (eg SSAT), please explain, without recourse to jargon, why If the aerosol optical physics is 'wrong' as you claim, the upward radiative flux would be reduced. Not increased as is in fact observed.
Nonsense above should read:
"Also, I find your posts barely comprehensible and suspect that this is far from accidental. For the benefit of others (eg SSAT), please explain clearly why, if the aerosol optical physics is 'wrong', the upward radiative flux from cloud formations above phytoplankton blooms is increased and not reduced."
BBD, you reference Vernier et al. 2011 as evidence that Hansen is right about the recent flat trend in GAT and aerosol negative forcing. However, when I read this reference I find that it only talks about aerosol levels and says nothing quantitative about their impact on GAT.
You then go on to say that relationship between solar cycle, GCR flux at surface and OHC is far from clearly established, which I cannot disagree with but then again I never said it was. After this you then try to undermine Dr Shaviv's objectivity by saying he made a 'gross overstatement' about OHC, so I guess I'd be quite within my rights to question Hansen's objectivity when he starts talking about CAGW causing the oceans to boil...
http://wattsupwiththat.com/2012/01/12/quote-of-the-week-dr-james-hansen-of-nasa-giss-unhinged/
...or would that be an unfair comparison?
I hope this is the right place and not too far down the thread to get an answer.
I am interested in the concept that the models which predict CAGW are tested twice a day by producing the weather forecast
- I think that is what is claimed?
This of course hinges on what constitutes an "accurate" forecast. The forecast I am most familiar with is the Inshore Waters Forecast, which I use to attempt to plan sailing trips (an excercise in frustration). These forecasts are issued twice a day for 24 hours and 48 hours ahead. My impression is that the 24 hour is sometimes accurate and the 48 almost never, clearly this is a lot less accurate than the Met. office claim. This is probably down to the definition of "accurate". I understand that a forecast is deemed accurate for wind if the actual was within +/- 1 Beaufort force of the prediction. This isn't great to start with, but when you consider that a Beaufort force is a range of windspeeds it gets worse. Where it really falls down is the fairly common forecast which says something like "Winds force 4 -7". As I understand it this will be counted as accurate if there are winds between F3 - F8, which isn't much use as a forecast!
By the same token it doesn't offer a great deal of validation to a model if it can only predict within such broad bounds.
I think the Met. office claim something in excess of 90% accuracy; I found several small scale studies on the web where people had compared forecast to actual and they all seemed to converge to something around 50% accuracy - can any statisticians confirm my impression that this means they are random?
Dave Salt
Yup.
DS
I didn't you did - I said Shaviv did. More precisely, he said that it was 'unequivocally demonstrated' in his 2008 paper. It isn't, hence my comment above. I didn't try to 'undermine' Shaviv - he has done that himself.
DS
Sorry - missed the Vernier question. The cooling effect of stratospheric aerosols is uncontroversial. What surprised people was that there were more aerosols than expected and the source was mid-scale equatorial eruptions 'boosted' by equatorial convection into the stratosphere. It very much looks as if Hansen was right though (boo, hiss): aerosols are offsetting the warming from CO2 more than previously thought.
BBD,
Is Hansen correct about the oceans boiling?
BBD, my point was that if Shaviv has undermined his position by making such a statement then, by your own criteria, Hansen has done the same, only more so. However, whether this undermines peoples trust in their scientific output (i.e. are they fudging the data to support their personal objectives?) is something for the reader to decide.
I note that you're quick to criticize people like Shaviv, Soon and Lindzen for their beliefs and actions but remain silent on the behavior of people like Hansen and Mann... I believe this tells us more about your objectivity than theirs.
Dave Salt; Roger Longstaff
My take on this is that Hansen is speaking about hypothetical extremes. He is clear that while there have been Snowball Earth episodes there has never been a runaway greenhouse. His position is no different from most climatologists: the current climate state is at the bottom of a U-shaped curve of responses - push it hard enough in either direction and you will get a Snowball or a Venus.
I doubt that we are capable of triggering a chain reaction leading to a PETM/end-Permian clathrate eruption that ultimately boils the oceans. The Venus outcome is the hypothetical bookend to the Snowball Earth but I suppose Hansen's point is that if we do somehow manage to release enough CO2 rapidly into the atmosphere it -could- perhaps drive the climate system into a unique hot state.
Discussing hypothetical outcomes is not the same as making a statement (as Shaviv does) that OHC increases and decreases by a far larger amount (>6x) than currently estimated in phase with the Schwabe cycle.
I don't think Hansen's statements are at all helpful, but DS is seeking to establish a false equivalence with Shaviv. That's not helpful either.
Thanks BBD,
I agree with you that: "Hansen's statements are (not) at all helpful", but not that: "His position is no different from most climatologists". I think that most sensible scientists would run a mile......
In my opinion Hansen, Mann and Jones, by their outrageous behaviour, have damaged the reputation of science in a most disgraceful way.
Listing to Hansen's words from 02:00 onwards, he clearly says that the runaway greenhouse "can" happen to Earth, so he's not just musing about hypothetical extremes; his words are meant to really scare people!
I remember walking away from my first exposure to Gore's video with the words "the prostitution of science in order to justify a political agenda" running through my mind. In the five years since then I have not read/seen/heard anything to change that opinion but have read/seen/heard much to reinforce it.
BBD, you're right to chastise me for trying to establish a false equivalence with Shaviv... his words are merely those of an inquiring scientist where as Hansen's are those of a political zealot!
Mydog at 12:37pm, you refer to a post at WUWT, about the physics of CO2 and thermalisation. I'm sorry, but I don't find that post at all convincing. Basically, as it explicitly states, it assumes that the atmosphere is at local thermal equilibrium at all times, even after a hypothetical step jump in the concentration of CO2. This is not correct. Such a rise in concentration would lead to an increase in absorption of IR, and the emission that otherwise maintains thermal equilibrium would lag behind until the temperature had risen a little bit. Roy Spencer, not the most slavish devotee to the consensus, said as much, in different words, in one of the first comments.
Like with the issue of back-radiation, the point is that the atmosphere is a heat engine, heated at the earth's surface, by the sun's visible radiation, and cooled at the top by IR emission to space. It is not overall at thermal equilibrium, and not all perturbations leave it at even local thermal equilibrium. The post at WUWT is wrong.
BBD is not a troll. He (she?) has always had an aggressive style and is now reflexively contrarian about pretty much all sceptical opinions expressed here, but just as the consensus is not wrong about everything ;-) nor is BBD.
Shaviv, to return to the original post, is not claiming that the climate models get the chemical physics of CO2 interaction with IR wrong. He's saying they seem to - consistently - overestimate sensitivity.
BBD, concerning the Vernier question, I'm not arguing cooling effect of stratospheric aerosols. I simply pointed to the fact that the Vernier paper says nothing 'quantitative' about their impact on GAT; something you seemed to be implying in order to support Hansen's hypothesis. Moreover, the logarithmic scale of Figure 5 shows explicitly how small the recent rise is compared to Pinatubo, so the idea that "aerosols are offsetting the warming from CO2 more than previously thought" seems not to be supported by this analysis.
I'll admit that quantitative impacts cannot be directly inferred from such graphs, so I'd be interested to see how such trends manifest themselves when you plug them into the models. However, if Michaels' is to be believed...
http://wattsupwiththat.com/2012/01/10/the-climate-science-peer-pressure-cooker/
...the results suggest a much reduced CO2 sensitivity, which tend to makes Hansen's hypothesis look even less believable.
Jeremy Harvey; thanks for your input. However, I have seen no definitive view on the thermalisation of the absorbed IR energy that fully convinces me of what is happening.
It seems the BBC PET bottle experiment, essentially the same as 19th Century experiments does not prove the point. One issue is that between 250 and 350 K, Cp for CO2 increases by 13.1% as the longer wavelength absorption bands develop. Happer resigned his job as Director of Research for the US DoE because of the liberties being attempted for this part of the science.
Nahle is looking at partial molar Cp data for mixtures of CO2 with the other gases. As one who was trained in this area of thermodynamics, it is the best way of getting data. I would not be surprised if direct thermalisation is quite low in which case all the IPCC's bets are off even without considering the new Phlogiston of 'back radiation'.
BBD: the palaeo evidence point clearly to extra warming of the Southern ocean when vast phytoplankton blooms occurred due to Milankovitch triggering instability of the ice sheet, hence dispersal of vast quantities of dust/Fe.
The one instance of modern research where higher albedo was apparently observed over much smaller phytoplankton blooms [the Antarctic is in Fe deficit] may be spurious.
Are you misrepresenting Stott et al. again?
Stott et al. (2007), concludes that slight changes in austral Spring insolation reduced SH sea ice extent. Consequent reduction of ice-albedo feedback (the dominant feedback in glacial climate states) amplfied the warming.
BBD,
Vernier shows the exact opposite of what you claim.
Here's his equatorial numbers (where most of the aerosols are) versus GISS's global average:
http://i43.tinypic.com/24p9g0y.jpg
There's not "more aerosols than anyone expected" you clown. Pinatubo's cooling was even overblown. It's worse than anyone thought James Hansen thought it was.
FergalR
Of course it does dear. That's why the paper is tagged:
And the abstract states:
May I ask for the source of the graph you link?
And can we have less of this 'you clown' crap? It's unnecessary. And in your case, unwise.
BBD,
Check the graphs on the GRL page where the abstract is.
My graph is digitized from figure 5 which has a logarithmic scale on the y axis. The recent aerosol peak is at 0.005 so you can see my digitization is correct. It's insignificant for global climate.
I'd advise you to check what the sources you cite actually say because you don't have a clue.
FergalR
It's odd how the graph you link to is rather different from the one presented by Vernier et al:
http://www.agu.org/journals/gl/gl1112/2011GL047563/2011gl047563-op05-tn-350x.jpg
How do you explain that?
BH - why do comments keep disappearing into moderation? It's... unsettling.
Squarespace have changed a setting on the spam filter. I am...communicating with them!
BBD,
Once again, the y scale is logarithmic in that graph otherwise it'd need to be printed on a billboard to show the detail Vernier found. Look at figure 3 which has a liner scale like my graph and you can clearly see it peaks around 0.005 - and far less at higher latitudes. I'm correct. It's insignificant.
You just fundamentally don't understand what you're waffling on about.
FergalR
Oh, I have a rough idea.
So, did -you- prepare the graph you link?
And - just by the by - how do you determine the aerosol loading found by Vernier to be 'climatologically insignificant'? Can you be rather more precise about this?
BH - thanks for the information. I wish you rapid success ;-)
BBD,
You clearly don't have any idea. Are you sitting on your elbows? To answer your questions:
Yes, I'm very proud of myself.
Mount Pinatubo is generally credited with temporarily causing about 0.2°C of cooling with 30 times as much SO2 as Vernier found in recent years. It's insignificant. Case closed.
FergalR
You have not answered my question: how do you determine that the aerosol loading observed by Vernier is climatologically insignificant?
I only mention this because Solomon et al. (2011) differs with you rather strongly.
BBD
I have a bad feeling about this.
[BH - fair enough; I'll leave it but might I be permitted a final question?]
FergalR
One other thing. You say:
I was under the impression that Pinatubo is generally credited with lowering GAT by about 0.8C (remember that the 1991-1992 El Nino would normally have raised GAT by 0.2C).
However I may be mistaken. Since the 0.2C estimate is generally accepted it must be widely supported. You will have no trouble in providing exhaustive references for it but in this case I will settle for five.