It’s a familiar story: An interesting paper gets published, there is a careless throwaway line in the press release, and a whole series of misleading headlines ensues.
This week, it’s a paper on bromine- and iodine-mediated ozone loss in marine boundary layer environments (see a good commentary here). This is important for the light that it shines on tropospheric ozone chemistry (“bad ozone”) which is a contributing factor to global warming (albeit one which is about only about 20% as important as CO2). So far so good. The paper contains some calculations indicating that chemical transport models without these halogen effects overestimate ozone near the Cape Verde region by about 15% – a difference that certainly could be of some importance if it can be extrapolated across the oceans.
However, the press release contains the line
Large amounts of ozone – around 50% more than predicted by the world’s state-of-the-art climate models – are being destroyed in the lower atmosphere over the tropical Atlantic Ocean.
(my highlights). Which led directly to the headlines like Study highlights need to adjust climate models.
Why is this confusing? Because the term ‘climate models’ is interpreted very differently in the public sphere than it is in the field. For most of the public, it is ‘climate models’ that are used to project global warming into the future, or to estimate the planet’s sensitivity to CO2. Thus a statement like the one above, and the headline that came from it are interpreted to mean that the estimates of sensitivity or of future warming are now in question. Yet this is completely misleading since neither climate sensitivity nor CO2 driven future warming will be at all affected by any revisions in ozone chemistry – mainly for the reason that most climate models don’t consider ozone chemistry at all. Precisely zero of the IPCC AR4 model simulations (discussed here for instance) used an interactive ozone module in doing the projections into the future.
What the paper is discussing, and what was glossed over in the release, is that it is the next generation of models, often called “Earth System Models” (ESMs), that are starting to include atmospheric chemistry, aerosols, ozone and the like. These models may well be significantly affected by increases in marine boundary layer ozone loss, but since they have only just started to be used to simulate 20th and early 21st Century changes, it is very unclear what difference it will make at the large scale. These models are significantly more complicated than standard climate models (having dozens of extra tracers to move around, and a lot of extra coding to work through), are slower to run, and have been used much less extensively.
Climate models today are extremely flexible and configurable tools that can include all these Earth System modules (including those mentioned above, but also full carbon cycles and dynamic vegetation), but depending on the application, often don’t need to. Thus while in theory, a revision in ozone chemistry, or soil respiration or aerosol properties might impact the full ESM, it won’t affect the more basic stuff (like the sensitivity to CO2). But it seems that the “climate models will have to be adjusted” meme is just too good not to use – regardless of the context.
Trrll, You have to start with a criterion for “better,” and depending on which criterion you choose, you will get AIC, BIC or some other metric/evidence function for deciding between theories. The nice thing about the information theoretic methods is that they start with concepts that are in some way fundamental–e.g. Kullbach-Liebler distance for AIC, or an optimial posterior probability distribution for BIC
RE: 51
Ray is right on with having to start with “a criterion” for “better” theory, but I imagine he wouldn’t disagree with me rephrasing that as “… a set of weighted criteria.”
Theories are evaluated against multiple criteria, which include not only the ability to predict, but also the ability to explain in the manner of feeling satisfying to a person (“explanatory power”); the ability to generate other, (possibly) better theories (“fruitfulness”); and so on.
There is diversity among scientists in how much they weight each of the criteria. Even a given scientist will weight the criteria differently at different times. There is no single, objectively correct, final-for-all-time set of weighted criteria. Often there is no single, objectively correct, evaluation of a theory’s degree of meeting even one criterion. Even the criterion of predictive power depends on precisely how you define the theory and precisely which observations you choose to compare to the theory.
Examples abound, of scientists whose personal judgment of a theory was doggedly more optimistic than the judgments of other scientists, but who turned out eventually to be correct. An example is plate tectonics. But the more (well-informed) scientists who agree in their evaluation of a theory, the higher the probability of that theory being correct.
People who are not actively engaged in the practice of science often react badly to what I’ve just written, because it makes science seem so subjective, arbitrary, random, and untrustworthy. The missing piece is what you can understand only by actively practicing science. The processes, rules, and rules of thumb all work together quite well, in a sometimes unnervingly non-waterfall way, to converge the conclusions on good theory and good observations. An example is plate tectonics.
Well not exactly spot on the subject but I have a question about Joyce E. Penner who recently some how made a science journalist on the Swedish Radio believe that the IPCC report Chapter 3 and 9 say that increased solar irradiance not greenhouse gases has contributed to most of the energy to the climate system since 1990. I have looked thru the chapters and briefly though her publications but really can’t find support for there claims. Any one know what they are on about? (changes in low cloud cover?)
(and that the recent “dip” in temperature could be due to low sun activity or changes in clouds)
Hmm… I know: http://www.skepticalscience.com/solar-activity-sunspots-global-warming.htm
(apparently she also suggested that the sensitivity probably could be less then 1,5)
Best Regards
[Response: This sounds confused. Joyce Penner is one of the top aerosol people and I doubt that she would have got the IPCC report so wrong. I would look to a mistake by the journalist in interpreting her remarks. Without a transcript it’s hard to say what was meant. – gavin]
Re 53, Solar irradiance or GHG’s being responsible for warming since 1990’s: My guess would be that what was meant is the global dimming – global brightening issue (but I could be way off the mark here):
The hypothesis is that an increase in aerosols (and subsequent decrease in solar radiation reaching the earth’s surface, hence “global dimming”) has masked some of the warming up to the 1980’s, but since then the aerosol loading has largely stabilized or even decreased, thereby having added to the warming by allowing more sunlight to reach the earth’s surface (global brightening). At some point the aerosol loading will stop decreasing further, and then the extra warming that the decrease in aerosol has caused will also stop. There were some interesting presentations about this at the EGU in Vienna. See eg this recent paper: http://www.agu.org/pubs/crossref/2008/2008GL034228.shtml. I do expect some discussion about these results though…
Hi again,
Yes that is what it mostly is about I guess, I only have second-hand information by mail exchange with the journalist. I have mailed Gavin some details I don’t know if he have time over to look at it but it would be interesting to here what he have to say about it… I have seen earlier comments from him on that area. http://www.giss.nasa.gov/research/news/20070315/
Well the Journalist claims:
That chapter 3 page 277 and 278 in IPCC and chapter 9 (3?) page 277 (278) say that the forcing from less particles is bigger then the forcing from greenhouse gases.
Chapter 9 page 674 and beyond, page 676 figure 9.3. shows that the decrease in reflected radiation is significantly less then what the models show. The numbers for the forcing for this he say is significantly bigger then the forcing from CO2 (during that time I guess) and that the numbers is in the text and that he thinks it is weird that it did not make it to the summary.
He further states that Penner had a poster at AGU 2007 about the fact that the models did not consider the increase in radiation.
Then he mentions Pinker et al in Science 2005 that supposedly show that radiation at the surface (less particles) have bigger forcing then the greenhouse gasses. Wild et al had an article on the same theme… there.
Chylek et al he also say have after IPCC published a report that said that the greenhouse effect at least should be half of what is supposed today.
He also mentions the “problem” with the models for the tropics that “should” increase 3 times more “a bit up” then on the ground if it is greenhouse gases that stands for the increased temperature… and that chapter 9 page 267 and past don’t show that.
I just got his reply to my mail so I haven’t had time to look at it but will try to do it later… thanks for the response.
Well just to let you know, I sent a short reply to the reporter when I got his mail mainly just stating that if you read the IPCC report you also se that there are lots of uncertainties around this and I also sent the article from NASA. And also said that I can’t find any published support for the claims that are made in the program. He then sent me this reply late in the evening.
“If you don’t find support for it blame IPCC they only use published data”
“the satellite measurements are global the increase in radiation mainly comes in 20n to 20s where most of the energy comes in but this is also evident for 60s to 60n figure in chapter 9”
“An interesting thing is that this manly is evident over the ocean which could point on an other explanation then clean air.”
“the “radiation balance” (sorry for the bad translation but I think you understand) there are a number of articles that backs up that it increases and there is no as direct measurements that couples greenhouse gasses to the increased to the increased energy in the system.”
“It also is interesting that the LW “radiation” have increased not directly what you would expect from an increase in greenhouse gasses.”
He then say that he wants to take a brake in the communication… (I made sure I had his boss on the mailing list).
But my complain is not that they talk about uncertainties of clouds or aerosols but the claims that where made in the program. This is one of maybe three really trusted science news sources in Sweden, so I think they should try to build the news on published articles…
1. The higher degree of radiation that got through in the 90s made it hotter and a decrease now lowers the temperature.
2. It’s not the last years lack of warming that is most troublesome, satellite measurements show that it’s not the greenhouse gasses that mainly have increased the energy in the system it’s the increased radiation from the sun (that get in due to clouds or less aerosols). The IPCC report chapter 3 and 9 say this, but it is not mentioned in the summary.
3. the models predicts the recent warming but that the large increase in radiation is not accounted for in the models.
4. the models say that it more or less is the greenhouse gasses alone that stand for the increased temperature when they really have had a large help from increased radiation.
5. if it is reported in the IPCC report that the climate models is wrong and that it is increased radiation and not greenhouse gases that could have the biggest effect on the last decades warming should it not have said so also in the summary that was presented for the politicians and public?
6. among other things the summary sais that the increase in temperature during the 90s was 0,2 and it lies between the modelled ranges 0,15-0,3 /decade but according to David Parker in the British whether service the last years cooling have decreased rate of the change to 0,13 i.e. lower then what the models show, ad to this that if about half of the increase in the 90s is due to change in radiation the carbon dioxide effect is far smaller then what the models are programmed for.
They then speculate abut how low the sensitivity could be.
So I objected against the jump in conclusions that this is well supported and said I think that it is up to debate what effect this have on the temperatures and that there also are other things pointing in the other direction of higher sensitivity, we just don’t know. And that it then is wrong by a respected science channel to extrapolate and guess what might happen. And then express it as very probable… So I asked fore published articles that supported what he said and I really cant say that I got any… will reed them closer later.
So any one that can help me whit what kind of conclusions that could be drawn from what the published literature says on the subject is most welcome. For example how much lower sensitivity or forcing could one expect or is it lower at all?
Best Regards
Magnus, Where on Earth (or elsewhere?) is your journalist getting his information? Chapter 3 doesn’t even address cosmic rays! It sounds as if he is just spouting denialist talking points. And for
God’s sake, the radiation actually reaching the ground has decreased by nearly 3%. This is what happens when you let ignorant food tubes report on science!
yes, well that is one of his points… also I think. That it increased during the 90s and then now is decreasing… so he thinks that less aerosols in the 90s contributed to the warmer climate then in the 2000s he say that the radiation decreased (due to less active sun?) and that this is why we se a “lack” of warming now. this would lead to the conclusion that CO2 forcing is much smaller then in the models because they “follow” the temperature without accounting for the “increased inlet of radiation” (clouds or aerosols)…
Now I could not understand where he got the info from and it seams to me that most of this is cherry picking and extrapolating and i don’t know what Penner actually told him but he said that she said that a doubling of CO2 could be much less then 1,5…
So this is why I want to know if there exist any publications that put any strength behind the low sensitivity…
I also want to apologise for my sometimes bad translations, hope that it doesn’t confuse you to much…
I’m also sorry that i haven’t had time to look closer in to this myself… looking up if the decrease in radiation during 2000 could explain lower temperature e.g. as I understood it before it was more likely to come from la nina or something combined, and why such a decrease would occur 2000 if aerosols really have that big effect, could it all be clouds and if so why? and how much of the aerosol effect is in the models… and so on.
This did help me with the chylek publication:
http://julesandjames.blogspot.com/2007/12/chylek-on-sensitivity.html
Magnus, Look here:
https://www.realclimate.org/index.php/archives/2007/11/global-dimming-and-global-warming/
The changes in the 90s were tiny–way too small to explain the temperature change unless you have significant positive feedback. And if there is a significant feedback that applies to insolation, it must also apply to CO2. Thus, trying to explain warming with only solar changes would–if it were possible at all–could actually result in a higher sensitivity to CO2.
There are >20 GCMs out there. Not one of them has a sensitivity less than 2 degrees per doubling–that ought to give an indication of the difficulty. Now consider that if someone actually accomplished this, they would probably become the most famous climate scientist on Earth! Must be damn hard!
It sounds like the journalists are definitely extrapolating too much, but the research that they seem to base their opinions on is not necessarily from the skeptical point of view. The effects of aerosols are very uncertain, and the global dimming – global brightening issue is one that could have a significant effect indeed, and it is undertaken by serious scientists. The journalists taking such research out of context and extrapolating wildly is off the mark though.
Some of the points you raise, Magnus: The SPM is a synthesis, and thus not all individual pieces of research need or should be mentioned there. Climate models take all known forcings into accoutn, not just greenhouse gases. See eg Hansen et al Science 2005.
Magnus Westerstrand (59) — In he second paragraph of
http://en.wikipedia.org/wiki/Climate_sensitivity
there are links to two important (IMO) papers on the determination of climate sensitivity and a discussion paper. I encourage you to start there.
[Ray Ladbury Says:
27 June 2008 at 7:00 PM
Mark and Guenter, Actually, there are several versions purporting to be what William of Occam actually said–and of course he said it in Latin, but I think the closest to the recognized form (translated) is: “Entities should not be multiplied beyond necessity.”]
Aye, my sister did Latin and Greek, but that’s the closest I got to it.
And I’d peg my version fairly close to that one:
“do not multiply the number of entities in an explanation needlessly”
Which is (as far as I can see) just saying WHAT constitutes an entity.
So if you have your pink unicorn theory then someone says “well, what about poink unicorn poo” and you have to then say “it evaporates”, you’ve added another entity in your explanation.
Having to add more and more codicils to your explanation is often a sign you have it wrong. Which is why “Dark Matter” is a hypothesis (at best): because we keep having to fiddle what it does to keep it fitting.
Problem is, we don’t have anything better, which is a downer. But that may show some more basic assumption is untrue (and that constitutes the reasoning for MOND et al).
(see, I’m not a climatologist, I did physics with astrophysics, but I’ve had to do numerical modelling using fluid dynamical questions, so I know how hard it is to get even an answer, never mind manipulate it so it gets a pre-determined answer…)
> “If you don’t find support for it blame IPCC
> they only use published data”
and
> … he said that she said …
I think this journalist has just illustrated _why_ the IPCC use only published data. Because gossip isn’t easy to peer review. Duh.
I hope you contact Dr. Penner directly and invite a response, now that you have the journalist on record in email about what he attributed.
Back on topic, this press release continues to pop up as news at various place I read.
They make the point that direct observation studies are useful — in later news I see mentions of science budget decisions being made. Was the timing and PR language related to
I thought I could blame the journalists but the actual press release says “chemicals … attack the ozone, breaking it down. As the ozone is destroyed, a chemical is produced that attacks and destroys the greenhouse gas methane.”
Chemically imprecise: “breaking … destroyed … attacks ….”
Is the paper any better about mechanisms and results? Or did they just observe less ozone and methane and say it is going missing?
Reporting from the bush…
I got a reply from Penner while I was away and she have bean “misinterpreted” so it’s the reporter trying to push his own agenda.