What is one to make of a recent press release and submitted preprint blaming global warming on the Tunguska meteor event in 1908? Well, although it is not unknown for impact events to affect climate (the K/T boundary event springs to mind) there are a number of hurdles for any such theory to overcome before it moves into the mainstream from the wilder shores of unsubstantiated speculation.
Firstly, one would anticipate that immediate effects of the impact on climate would be strongest near the time of the impact (allowing for some inertia in the system) and decay away subsequently. Secondly, the timescales for any mechanism associated with the impact (in this case disruption of the atmopsheric water vapour) would need to be in line with the change one hopes to explain. And thirdly, one has to show that this explanation is better than the alternatives. Unfortunately, none of of these requirements are met by this hypothesis.
An impact hypothesis is usefully contrasted to the impacts of a large volcanic eruption like Pinatubo in 1991. There was a very clear dip in temperatures a year or so after the eruption and a subsequent relaxation back to normal. No such event (warming or cooling) is recorded in 1908 to 1910. The timescales for water vapour in the lower atmosphere is on the order of days (see our previous post on the subject), while in the stratosphere it is a a few years. But there are no reservoirs of climatically important water vapour amounts that could still be causing the impact effect to be felt (and to accelerate!) almost 100 years later. And finally, current theories based on greenhouse gas increases, changes in solar, volcanic, ozone , land use and aerosol forcing do a pretty good job of explaining the temperature changes over the 20th Century. It’s very hard to see what this idea has to add to that.
In an additional twist, it is suggested that atmospheric nuclear tests from 1940s to the 1970s masked out the effects of the impact due to the supposed mixing up of tropospheric water vapour into the stratosphere after every explosion. This is even odder since stratospheric water vapour is actually quite a significant greenhouse gas, and had this occured to any large extent, it would have been a warming factor, not a cooling one.
So while the physics being invoked here is barely worth discussing, a more interesting question might be why the University of Leicester thought that this was worthy of a press release in the first place, and why this got any traction in the media at all. True, it didn’t get much attention, so maybe there is some hope for science journalism after all…
Thank you.
The Leicester press release made it to the Science News section of the U.S. Google News today, and, based on what else was available on the web, it seemed plausible to me. Without your posting helping me through the thinking, I would have wasted brain space etc. on the idea.
just how often do Tunguska scale events occur anyway? I seem to recall that they occur every 100 years or so. And even if they were rarer, and the claimed effect were true, such events would coincide with warmings in even recent records which have nada to so with man and his CO2 and nukes and such.
I put the words in the title into google news, and I only got 1 dupe of the U Leicester report, and one other article , which is claiming the lack of press traction is a case of censorship. physorg, they claim, put it up briefly and then took it down.
It’s too bad physorg didn’t make the old link re-direct to an explanation of how unlikely it is that Tungaska 1908 caused global warming, but such things take time and energy.
The claim that ‘debunkings’ or ‘alternative explanations’ of global warming get censored seems to get an awful lot of traction, despite the seemingly obvious success of many denialist claims. That seems to me to be a more serious problem than one seemingly obscure article claiming Tungaska 1908 caused global warming.
Well I laughed out loud whilst reading it. Personally I think it’s a piss-take. In fact, I wish I’d written it. [ad-hom deleted – moderator]
Caramba! I just found it on the University of Leicester website – this is real!
[irrelevance deleted -moderator]
The author of the Tunguska theory, Vladimir Shaidurov, is the winner of the most prestigious scientific award in Russia for 2004, the State Prize, and he is the director of the Computer Modelling Institute of the Russian Academy of Sciences which itself makes the attempts to humiliate him slightly inappropriate.
[Response: This is let through in answer to previous comments. To all commenters, please, no ad-homs or diversions on to non-scientific topics. -gavin]
PhysOrg: http://www.physorg.com/news11710.html
PhysOrg comments: http://forum.physorg.com/index.php?showtopic=5407
ARXIV abstract, offering link to full text: http://arxiv.org/abs/physics/0510042
CiteBase: http://www.citebase.org/cgi-bin/citations?id=oai:arXiv.org:physics/0510042
The “story being censored” claim linked to above is from a secondary source — it’s repeating a claim blogger John Ray found, he says, on Free Republic. I left him the working links in his comment mailbox.
I’m intrigued to see that, following the failure of Russia’s “Academy of Sciences” to contribute to the unprecedented joint report by so many other major national academies prior to the G8 meeting, this kind of third-rate tabloid speculation is now coming out of that country.
This is not in any way to belittle the professional integrity of Russian climate scientists, several of whom I am honoured to call friends, but to wonder at the degree of callous control by politicians.
[gratuitous comment deleted – moderator]
regards,
Lewis
[Response: Minor correction. The Russian Academy of Sciences did sign on to the joint statement. -gavin]
Gavin – my apologies, I was misinformed on this.
For the record, and since the meteorite theory claims to make the G8 report wholly redundant, could you possibly list the national academies that did sign ?
regards,
Lewis
Every G8 nation and three large developing nations.
Brazil, Canada, China, France, Germany, India, Italy, Japan, Russia, the United Kingdom, and the United States of America
http://www.academie-sciences.fr/actualites/textes/G8_gb.pdf
Why Leicester?
In reading this and other “controversies” materials, it seems to me that there is a handful of agressive seats of learning, always eager for “scoops”.
To my mind the third of Gavin’s “three hurdles” has a whiff of begging the question. Imagine a creationist setting up some such hurdle to a Darwinian “… and thirdly, sir, your theory can’t be right as it implies the world was not made in seven days – which is patently absurd”. Moral: You can’t set up “agreement with (Gavin’s idea of) the current consensus” as a precondition for a competing theory! Unless of course you’re a paid up member of the “debate is over” school of climate change. In which case why carry on the discussion?
[Response: The current consensus has arisen because it does the best at explaining the observations and has been shown to have predictive power. New ideas need to do better than that in order to overturn current ideas. Pretty basic stuff really. – gavin]
(Re: response to 12) Perhaps we can agree with the proposition that the winning theory should be the one that “does the best at explaining the observations and has been shown to have predictive power”. Indeed Gavin claims that such a meta-scientific idea is “pretty basic” (if so, one wonders what Karl Popper et. al. found to do all day). Certainly we can tick off the cons (and, who knows, even the pros?) of theory A in contrast to theory B. But I am saying that I don’t think it should count as an additional con against A that, unfortunately, B has got there first and is “true” (whatever our meta-scientific view of that is). That would be begging the question surely.
[Response: No theories in earth science are ‘true’ in an absolute sense – they simply have more or less explanatory power. If theory B has more explanatory power than theory A it will be preferred regardless of which one got there first. Even if theory A is only a slight modification of theory B, it still has to explain more than it adds in complexity. In this case, theory A ‘Tunguska’ has very little explanatory power, and in many ways is inconsistent with observations that theory B (the ‘consensus’) explains quite handily. Even Popper would then reject theory A in such a case. -gavin]
No wonder action on reducing CO2 levels from human activities is very slow in coming. Why do Universities press release this stuff before it has been peer reviewed. Surely Peer review should decide before something is considered worthy of being published in respected scientific journals and hence seen as the truth by the public, the press and Governments around the world.
Something is wrong here surely when junk science once again is allowed to grab headline just because it sounds good and makes for a dramatic effect.
Dear realclimate
I know this is bit off topic but it is a genuine query. When GISS (or CRU) are calculating the monthly global temperature anomalies which stations do they use from South America. Presumably to qualify for the GISS record they would need to have a complete (or near) record for the 1951-1980 period (1961-90 for CRU) and one which runs up to the present day.
If you have a list I can reference I would be most grateful. It’s just that I’m struggling to find even one that fits the required criteria.
thanks
TIPPING POINTS —
First my reaction to such “not human sources” stories (since I’m not a climate scientist) is — even if that meteor were to have some impact on GW, we still have our GHGs that we are currently emitting. We can’t control meteors (unless we do some DEEP IMPACT thing), but we can reduce our GHGs, so lets get to it. We have to do what we can & reduce even more in the face of such uncontollable threats….which brings me back to:
RUNAWAY GW (as usual)
I read today that GW had reach a 2nd tipping point (see link), that the earth will continue to warm even if we completely stop emitting GHGs — and that we’ve already reached that point (I think this is not news, that we have 2 degrees in the pipes, but I didn’t read the sci jnl article mentioned in this news story): http://www.climateark.org/articles/reader.asp?linkid=53930
I’m thinking of a 3rd tipping point. Okay, there’s more warming in the pipes from what we’ve already emitted, and nature is also net responding to that warming by giving off more GHGs. A 3rd tipping point would be when really serious positive feedbacks start kicking in — like deeper & deeper melting permafrost releasing bigger pockets of methane, and melting ocean clathrates.
In other words, it could get worse, so we have to really really redouble our efforts to reduce GHGs. And with the additional future possibilities of those pesky meteors, volcanoes, increased solar radiation (& for heaven’s sake, let’s stop nuclear testing) — well, we’ve got to reduce our fossil fuel consumption by at least 90% just to offset those. Luckily Amory Lovins says we can do that. So let’s get to it.
Pali Gap –
there would appear to be a further requirement for theory A-Tungusta to gain credence over theory B-AGW, which is that theory A must also describe the mechanisms by which it prevents the demonstrable warming effects of recorded anthro-GHG outputs from causing the observed global warming.
regards,
While I agree, the theory of the Tunguska Event is far-fetched, I was under the impression that some kind of change has occurred in the mesosphere (thereby causing the noctilucent clouds) and that the exact mechanism creating them (dust, C02, methane, whatever), is still under investigation. My point is only to ask a question, not to refute AGW: Are we SURE that the changes to the mesosphere are DUE to Greenhouse Gasses?
Isn’t (hasn’t) NASA planning to send a satellite to investigate this anomaly (the Aeronomy of Ice in the Mesosphere satellite, or AIM for short)?
Perhaps the usual advice to fledgeling physicians is relevant here. “When you hear hooves, think first horses before you think zerbras.” It is certainly possible that there are zebras around affecting one or another aspect of climate, but greenhouse gases are rather obvious horses. The sceptic argument in these cases seems to be that I can explain observed warming by some rather obscure cosmic ray effect or meteor collision effect, so greenhouse gases must after all have had nothing to do with the matter. Such an argument by itself is insufficient. It must also be explained why greenhouse gas increases, the most obvious cause, have little or no effect. Either that, or the proposed obscure effect must be supported by overwhelming evidence.
The authors also appear to suggest that temperature is driving GHG concentrations, rather than the other way around:
…Therefore the rise of greenhouse gas concentration is more a consequence of warming but not a main reason.
Hypothesis 2: The above mentioned variant of self-stimulated process (with a permanent rise of average absolute humidity, and resulting concentration of carbon dioxide and other greenhouse gases) was launched in 1908 after the atmosphere reconstruction due to the Tungus meteorite. …
That’s hard to reconcile with the data, at least for CO2.
[Response: Excellent point. Anyone claiming that “the rise of greenhouse gas concentration is more a consequence of warming” must be very unfamiliar with the basic evidence. It is beyond reasonable doubt that the current rise in CO2 is anthropogenic – we have summarised the evidence here. Not only do we know how much CO2 we emitted (more than is now left in the atmosphere – which means that the natural reservoirs have taken up part of our CO2 emissions, rather than having released CO2 in response to a climate change). That the increasing amounts of CO2 in the atmosphere come from fossil fuels was already demonstrated by isotope analysis in the 1950s. CO2 increases not only in the atmosphere but also in the global oceans – this is documented by 10,000 measurements – and very likely in the biosphere. And it would be difficult to argue that through a natural climate change, CO2 has suddenly increased to values about 30% higher than at any previous time for the past 650,000 years, and that this occurred by chance just at the same time as humans released more than enough CO2 to explain the rise. -Stefan]
Here’s anaother good one:
“Global warming linked to cosmic rays”
http://www.canada.com/nationalpost/news/story.html?id=13ef7006-c549-4543-8ed8-89b8f4ca63d6&k=42927
“A prominent University of Ottawa science professor says what we know about global warming is wrong — that stars, not greenhouse gases, are heating up the Earth. …”
[Response: Sometimes it seems like people are desperate to find something, anything, other than GHGs to be responsible for GW. Maybe they should all get together and have their own mini-IPCC and see if they could get their story straight – William]
The article exaggerates the man’s statement — he’s just saying that variation in cosmic rays can affect cloud formation. Nothing outrageous there.
[Response:Indeed one should not judge what people said just on the basis of newspaper reports. But in this case, Veizer’s own writing goes even further than the newspaper report – see our analysis of his key arguments here. -Stefan]
All the natural forcings can change the Earth’s climate — looking at the record as it’s teased out by researchers, there’s a huge number of different things that seem to affect climate at one time or another.
It seems clear that when something like a change in the sun warms up the Earth, or the Earth’s orbital changes warm it up, that’s followed by an increase in carbon dioxide released.
Simply increasing carbon dioxide levels — by hitting the planet with a large rock and causing a massive dieoff, or exposing something like the US western deserts’ coal beds long ago and having them catch fire and burn off — also causes warming. The physics of atmospheric CO2 and warming seems inarguable — no one anywhere is claiming that Arrhenius was way wrong about the physics, right?
The desperation seems to be to find any way to claim that producing a huge pulse of carbon dioxide from fossil sources can’t be all that big a problem — but nobody who does math seems able to defend that argument, it’s just political handwaving claiming the little effects of other things must somehow be greater than the big effect we know is due to human activity, because, well, because they must, because they profit us.
That’s why economics isn’t a dismal science, it’s a happy-face science — because it’s always possible to put costs off the budget (externalize them) and show a profit on paper.
But as to the various identified causes of warming:
“There are nine and sixty ways of constructing tribal lays,
And every single one of them is right!”
http://whitewolf.newcastle.edu.au/words/authors/K/KiplingRudyard/verse/volumeXI/neolithicage.html
Shaidurov is interested in the surface temperature trend decrease just prior to 1906 that is followed by a steady increase to about 1940 (and offers Tungusta). Then he notes the oscillating period from 1945 to 1976 before another steady increase starts again (I think he believes nuclear tests dampened down the Tungusta effect). Is there an AGW alternative explanation for the features on the graph that catch Shaidurov’s eye?
It’s not an either-or question. Theorists need to put numbers on their contributions, to make them possible for scientists to think about!
The sum total of all the different things that are happening — known and unknown — results in the changes (including changes we don’t yet know about — like what’s happening to temperature and dissolved CO2 in the deep ocean over recent time — we don’t have good data yet on that huge volume).
Shaidurov needs to come up with numbers people can do math with, to get his idea into the large group that are included in models and weigh this possibility along with others — correlation is not causation, they tell me.
Hank – that sounds right! “correlation is not causation, they tell me“. Yet isn’t that pertinent to this link of Gavin’s?
I’m interested in this comment by Gavin – “current theories based on greenhouse gas increases …do a pretty good job of explaining the temperature changes over the 20th Century“. Also the comments by Lewis and Leonard setting conditions on competing conjectures. Is it fair to say that Shaidurov is attempting to explain something (in a challenging and bold way) that is possibly an anomaly for the accepted AGW consensus?
Re #21: It is also somewhat deceiving of Canada’s National Post to present this as some sort of new hypothesis. In fact, Veizer’s work has been out there for a few years now…and long enough to be pretty much debunked (at least as an explanation of the current warming): http://www.bbsr.edu/Press_and_Pubs/pr2004/prjan2904/prjan2904.html
[Response: Also by RC: https://www.realclimate.org/index.php?p=153 :-) -William]
Re Pali Gap, 22:
What follows are the best guesses of this non-climatologist. (Corrections appreciated!)
The steady increase to 1940 is partly due to increases in human-emitted greenhouse gasses, but also partly due to increases in solar radiation. The fluctuations between 1945 to 1975 are due to mostly human-emitted sulphates blocking sunlight (thus counteracting the still-rising GHGS), and also due to fluctuations in solar radiation. Post 1975, human-emitted GHGs rise so fast they overwhelm all else.
See this graph (and then hit the ‘back to text’ link at the bottom for context). It graphs the forcings which have acted as heating or cooling forces on our climate. Note the graphs do not all have the same scale on the left side; solar, which has the least variation since 1750, ranges from maybe -0.37 Wm^2 (depending on reconstruction), to +0.35 Wm^2 . Well-Mixed Greenhouse-Gasses (WMGG) starts at 0 and ranges up to almost 2.5 Wm^2. Also, the 0 axis on each graph is relative to an appropriate historical average, not absolute. Compare to the Gisstemp or CRU temp graphs. The steady temp increase to about 1940 matches up well with the rise in the solar radiation shown graph 6.8 (d), and also with the similar-sized rise in WMGGs, shown in graph 6.8 (a). I believe that explains said rise (and also the many reports of warm temps in the 1930s).
From 1945 on, notice the solar radiation fluctuates rather than rising. WMGGs continue to rise. Now look at graph 6.8 (b), look at the sulphates line. Starting at about 1945 is a strong increase in the cooling effect of sulphates (negative numbers on the graphs indicate cooling effect). The increasingly negative sulphate forcing counteracts the rising WMGGs, and then some, resulting in weak cooling from 1945 to about 1975 . Past 1975, rising WMGGs nearly overwhelm all else.
One feature you refer to, which I haven’t explained, is the cooling which ends in about 1906 or so. 6.8 (c), the solar radiation graph, seems to show a weak decrease in solar forcing from about 1898 to about 1906. That may be the explanation.
A similar graph, which sorts the forcings differently, is here.
Please note that above, I intend to speak only of forcings resulting from various factors, not raw amounts, although my phrasing is admittedly ambiguous. Also, forcings are enhanced by positive feedbacks (like water vapor), dampened by negative feedbacks. and modulated by natural cycles of various lengths.
Finally, a realclimate decade-by-decade re-hash of the effect of various forcings on the climate, from about 1880 to the present, would be much appreciated. :-)
21:
What may be instructive is to read some of the comments and discussion on Shaviv and Veizer’s GSA paper.
I heartily recommend those seeking:
to read the discussion. Hmmm. That covers about everybody, I guess…
Best,
D
Shaidurov won! He wrote exactly: “The purpose of this report is to open the debate and to encourage discussion among scientists.” Scientists are discussing. Shaidurov achieved his purpose, at least, partially. Most of the statements of his opponents are of the type “we know the truth.” My congratulations! I am not an expert, but have PhD in Data Mining. The only question I would like to ask you is: is your climate model the result of fitting? How many parameters did you find by fitting? Is there a small place for doubt? (This is, of course, one question.)
[Response: Let’s not mince words here. There is not anything of scientific interest to discuss in Shaidurov’s paper. The errors he made in his argument were very elementary. He completely failed to understand the time scales involved in the atmospheric hydrological cycle, or the processes governing atmospheric water vapor. He also blundered by failing to realize that the mesosphere has so little
mass that it is very optically thin, so that mesospheric water vapor has an essentially negligible effect on climate. He failed to understand that there is abundant independent evidence that CO2 increase is due to human activities, and cannot be regarded as a consequence of warming. There is a bizarre claim about the pressure dependence of the freezing point of water at low pressures, for which the only support given is a reference to the general home page of the University of Waterloo science departments. The discussion in the paper (which I just wasted about 20 minutes reading) is full of other elementary misconceptions about the physics of climate, and for that matter, about basic physics as well. The interesting thing about the affair doesn’t reside in any scientific issues raised. The two questions are these: How could somebody like Shaidurov with a basically sound scientific training fall prey to so many elementary errors when a brief consultation with a basic text, the most cursory discussion with a colleague who knows the subject, or even with a reasonably well-educated undergraduate, would have made the fallacies evident? How could a reasonably respectable University like Leicester issue a press release involving such a supposedly revolutionary result without screening it with an independent party who knew the subject? Among the many egregious faults of the press release is its misquote of Dessler’s book; the quote seems to imply that water vapor changes are not incorporated in models (something also implied in Shaidurov’s manuscript), and that human activities can’t change water vapor. Dessler, of course, says nothing of the sort. As all regular RC readers know, anything that warms the climate (e.g. CO2) has an indirect effect on water vapor, through the water vapor feedback. Peer review will weed out Shaidurov’s not even half-baked idea before it gets much farther, but what surprises me is that Leicester’s public relations department was so sloppy. –raypierre]
Re #29
Bayesian reasoners always attach probabilities to hypotheses and often to data. Hypotheses are compared by the probability that they explain the data. The hypothesis which best explains the data is that supported by the weight of the evidence. Here are some of the details: Given data D, treated as certain for simplicity, suppose there are two competing hypotheses, H and K, to be compared. Determine the probability of the data D given H, p(D | H). The same for K, p(D | K). Now compute
10 log( p(D | H)/p(D | K) ), decibans.
If this exceeds 1 deciban, the weight of the evidence supports hypothesis H. If less than 1/2 deciban, the weight of the evidence is inconclusive.
So for the baysian there is always room for doubt. The chosen hypothesis is simply the best (so far). We all do, in an intuitive manner, what I have described above, say some bayesians. From the original posting by Gavin and the subsequent discussion in the comments, my reading is that the weight of the evidence strongly favors the standard GHG theory over the Tunguska theory, by an estimate of many, many decibans.
Zhenya, see this glossary of model types from the Hadley centre. To put it another way, modern climate models are simulations of physics – thermodynamics, fluid dynamics, some chemistry, and in some cases a little simulated biology. They are not the result of a ‘fitting’.
There is also a theory that the real cause of global warming is extraterrestrial beings who have for over a century systematically manipulated the development of human technology to ensure that its waste products would alter the composition of the Earth’s atmosphere, e.g. increasing the levels of CO2 and methane, to make it more hospitable to their alien biology, in preparation for a large scale invasion. The paper under discussion here has got it right, except that the Tungaska 1908 event was not caused by a “meteor” but by an alien weapon that was exploded to “jump start” the process of transforming the Earth’s atmosphere. This has been known since documents describing the extraterrestrials’ plan were recovered following the crash of an alien spacecraft near Roswell, New Mexico in 1947, however this theory is being censored by a worldwide conspiracy of climate scientists to cover up the existence of the extraterrestrials. I have to go now; the men in black are at the door.
Dear llewelly,
I apologize so much, but you (and your link) did not answer my question at all. You write, for example, “some chemistry.” It is nice, but where your take the kinetic constants, for example? From the first principles? I don’t trust. It in not a detailed model. There is a hierarchy of fitting, and you change your model after any significant event. Please ask any chemical engineer (real engineer, not a “paper” one) about models of a catalytic reactor “from the first principles.” We cannot produce a model for so simple device without fitting, and you SERIOUSLY tell me about your simulation that is “not the result of fitting.” Let us be modest, please. (And about simulation biology, again, is is even more vague. It gives nice qualitative picture, helps us to understand reality, but ability of quantitative prediction… Let us be modest, please.)
Stefan’s argument:
“CO2 has suddenly increased to values about 30% higher than at any previous time for the past 650,000 years, and that this occurred by chance just at the same time as humans released more than enough CO2 to explain the rise”
misses one possibility.
The nuance he misses is that we started using fossil combustion because other resource limits, related to climate and population, limited our choices.
For example, if the receding ice no longer offered enough land for a growing population, then we would have to resort to higher efficiency conversion to extract more productivity. England was hit hard by the little ice age and the depleting forests, they adapted to coal and the industrial revolution was born.
Was this pattern local? Yes, but it gets duplicated. The rise of oil combustion in the U.S. concided with the completion of our expansion west.
So, the question that I always ask is. If we had kept our population limited and used available surface energy, then when would the real ice age start? The Vostok co2 measuremns seems to show that a rise on co2 was well under way by 8,000 bp, and had reached nearly ice age levels by 1930.
Re #30
Dear David,
Perfectly! Your “decibans” are very good, thank you, I really enjoy.
The only thing, finally, just now I read the Shaidurov paper (not only the abstract and this PR). It seems unbelievable, after all our discussion, but he did not object the GHG arguments. He just told: Look, so perfect piecewise-linear trend. And where are the break points? This mysterious Tunguska Event is at the first? Strange… Let us discuss. This coincidence may be not by chance. There were many atmospheric anomalies fixed after this event… and so on. As I understand, he is absolutely not sure in his explanations, did not call them explanations or theories, just a hypothesis.
Have a nice day, I should leave (a train, sorry).
Zhenya, here are some RealClimate articles I should’ve linked in my earlier post: Modeller vs. modeller and Chaos and Climate which I found helpful, especially the former. Unfortunately, they are not exactly what you are looking for.
Note, at one point you refer to ‘your simulation’. I don’t have a simulation – as I have explained in previous posts, I am not a climatologist. My reply was simplified in part because your post was vague, and in part because my knowledge of climate models is limited. What you meant by ‘fitting’ was not at all clear. In many past discussions I have had, various people (not you) have used ‘fitting’ to mean a pure statistical fit. I assumed – unjustly, it now seems – that by ‘fitting’ you meant a pure statistical fit. When I said ‘They are not the result of a fitting’, I should have said: ‘They are not the result of a pure statisical fit’. Pardon my oversimplification! Unfortunately, I have niether the time nor the understanding to give a complete explanation of the relationship between models and statistics. I don’t even have any good links. :-(
Hopefully Gavin will speak up; he’s done climate modeling, with the GISS GCM .
Pali –25 –I don’t think so, no. Read the response Llewelly posted in 27, he points to the method for figuring out how much effect a given process has, and adding them up. There are a lot of things going on. Tunguska happened to hit at a particular date, but one about the size that made Tunguska comes along every 100 to 300 years or so, on average. Not all that big a deal compared to the strength of other forces, unless someone can come up with a mechanism. That’s the difference here — coincidence is “at the same time” but doesn’t imply any causation.
Now, CO2 and warming, there’s good physics and math explaining how changing CO2 levels causes Earth to retain heat, and it’s not new either.
See this example of how the math is done for CO2:
http://www.aip.org/history/climate/Radmath.htm
To nail down whether something like Tunguska can make a big difference, you’d want to come up with estimates for the corresponding numbers for how much dust the meteor left at what altitudes, what the chemistry was that would affect the high clouds, how the nuclear tests would have affected them, and what the result would be. Sum that with all the other known forces acting on climate (some plus, some minus).
Note that the USSR did a very large number of high altitude nuclear bomb tests in the far north. Someone ought to come up with a mechanism for how those changed the climate, if we’re going to take those into account.
Nice idea, nice coincidence, now someone needs a physical mechanism that would explain causation and some numbers to calculate the likelihood.
There’s no big unexplained problem that this new notion would satisfactorily explain — it’s simply another possible idea to which support will or won’t be discovered.
Note he has stated assumptions for the altitude, the mass and the composition of the meteor, for example. Those are assumptions. Compare those to other people’s estimates of how high it exploded, into what sort of material — you can come up with a wide range of possibilities (“error bars” around an estimate). What difference would it make if the assumptions differed? We have no idea ’til he comes up with a mechanism and some numbers. Hope he does. But I suspect this is a ‘talking point’ article not one that’s going to show up in a refereed science journal.
Just my hunch. Look at those links in 27, they ought to answer your question.
[Response: It’s not a “nice idea,” and it’s not even a “talking point” article. There is no data analysis in the paper other than the author’s rambling on about the the shape of the well-known graph of instrumental temperature records. The physics behind the supposed mechanism is ill-informed (at best). It doesn’t have a prayer of a chance of being right. Any attempt to follow up this idea more scientifically would just be a waste of time. –raypierre.]
Re 23,25,27
Eyeballing Shaidurov’s graph, it strikes me how small the oscillations he describes are. That brief episode strikes me as well within natural variability and error bounds; I’d be OK with calling it a wiggle, but to see “oscillatory behavior” takes a leap of faith. Humans are good at pattern recognition, but also good at spurious pattern recognition.
The difference between the model fit Gavin linked and Shaidurov’s verbal explanation of the temperature trajectory is that the former represents output of a model that embodies a physical explanation of the phenomenon and integrates as much information (e.g. other forcings) as possible. Assuming it also passes basic tests like robustness in extreme conditions, one could start to have some confidence that the fit is more than coincidental. Shaidurov has a long way to go to reach that level – but then he did say “The purpose of this report is to open the debate and to encourage discussion among scientists.”
Pali, here’s another good example of why it’s important to check the actual math before relying on pictures. Pictures have to have some math behind them if they’re telling us anything. As Ronald Reagan memorably said: “Trust, but verify.”
Here’s a classic example, for solar effects, from
http://stephenschneider.stanford.edu/Publications/PDF_Papers/DamonLaut2004.pdf
“Analysis of a number of published graphs that have played a major role in these debates and that have been claimed to support solar hypotheses [Laut,2003; Damon and Peristykh, 1999, 2004] shows that the apparent strong correlations displayed on these graphs have been obtained by incorrect handling of the physical data.The graphs are still widely referred to in the literature,and their misleading character has not yet been generally recognized. Readers are cautioned against drawing any conclusions, based upon these graphs ….”
Here’s another peculiar thing about the press release. The press release claims that the work is under consideration for publication in the journal Science First Hand. However, a search on Google and on a number of University library catalogs doesn’t reveal any trace of a journal by this name. The closest thing I found on Google was a newsletter about an NSF-sponsored program to help Middle-School students with science projects (goodness I hope Shaidurov’s project wasn’t one of those!)
So, has anybody located a journal called Science First Hand?
It’s a Russian journal. I had assumed http://www.sciencefirsthand.ru was it. They have an English version, but not all the text is translated.
[Response: Thanks for that information. Google finds it if you search “sciencefirsthand”, but not if you put spaces between the words, which is what I was doing. If this is indeed the journal in question, it appears to be a popular science magazine rather than a professional journal. That means that the idea isn’t even being submitted to peer review in the usual sense. –raypierre]
Tunguska, estimated at somewhere in the range of 12 to 15 megatons and exploding somewhere around 5000 to 8000 meters elevation, would show as a new dot on this chart — a bit higher, and not the largest of the explosions charted here:
http://www.johnstonsarchive.net/nuclear/tests/hob.gif
I got curious about what in the world Shaidurov might have meant by his mesospheric freezing point graph. Just as an exercise, by playing around with Clausius Clapeyron (once I looked up the conversion factor from mm Mercury — the units used by Shaidurov — to Pascals) I figured he was actually trying to talk about the saturation vapor pressure, not the freezing point. If this is what he meant, he seems to have confused partial pressure of water with total atmospheric pressure. Even correcting for this, the graph only shows what is standard knowledge in mesospheric thermodynamics — the mesosphere rarely gets cold enough to make water clouds. Shaidurov seems to be trying to argue that since water doesn’t condense easily in the mesosphere, it can stay around for a long time. His argument falls apart, though, because the partial pressure of water vapor in the mesosphere is so low that it has almost no effect on the radiation budget. Hence, it wouldn’t even make any difference if Tunguska could affect the mesospheric water vapor content on the centennial time scale. (Not that Shaidurov has supported such a long residence time for mesospheric water vapor either.)
Gavin says,
“In an additional twist, it is suggested that atmospheric nuclear tests from 1940s to the 1970s masked out the effects of the impact due to the supposed mixing up of tropospheric water vapour into the stratosphere after every explosion. This is even odder since stratospheric water vapour is actually quite a significant greenhouse gas, and had this occured to any large extent, it would have been a warming factor, not a cooling one.”
Does this mean that the hypothesis of nuclear winter does not survive testing by modern climate models?
Re 34,
According to d13C evidence, the pre-industrial holocene climate and CO2 levels are caused by natural causes, not anthropogenic ones; see Broecker & Stocker 2006, EOS 87,3. http://www.agu.org/journals/eo/eo0603/2006EO030002.pdf (AGU membership required)
[Response: Nuclear winter is not supposed to have been caused by water vapor, but rather by soot injected into the upper atmosphere from secondary fires caused by nuclear war. It’s certainly true that a high soot layer distributed globally would shut off the hydrological cycle and tropospheric convection, and cause the surface temperature to go down to -20C or so for however long it took the soot to settle out of the atmosphere. Where nuclear winter petered out, as a major threat was in the question of how global the soot distribution would be, and how much soot would be injected by firestorms, vs how much would be rained out locally. With realistic assumptions about soot injection, it doesn’t seem that nuclear winter significantly alters the already grim calculus of nuclear warfare. It’s a moderate additional stress on society, but basically not such a big deal in comparison to the enormous direct impacts of blast and long-lived radioactive fallout. By the way, the story of nuclear winter provides an excellent example of how good science is at weeding out “alarmist” predictions that aren’t supported by science. In this case, liberals and pacifists had every reason to believe in the validity of the nuclear winter theory, as it provided additional arguments against strategic doctrine based on pre-emptive nuclear strikes. Nonetheless, the scientific community evaluated the idea very fairly, and in the end came to the conclusion that the initial predictions of nuclear winter did not hold up against more detailed examination. This contrasts with the situation of global warming, in which scientists have become more alarmed the more they have studied the problem. –raypierre]
http://physicsweb.org/articles/news/10/3/13/1
Looks like increased Hurricane intensity is being caused by higher sea surface temperatures.
And now.. “Global warming linked to cosmic rays”
http://www.canada.com/nationalpost/news/story.html?id=13ef7006-c549-4543-8ed8-89b8f4ca63d6&k=42927
Maybe Realclimate team has already begun writing about that.
“…Jan Veizer says high-energy rays from distant parts of space are smashing into our atmosphere in ways that make our planet go through warm and cool cycles..”
Not an easy situation this one about understanding Global Warming precise culprits, when everyday there are new hypotheses about this most important situation.
Madre MÃa!!
Re, grundt, 46:
Veizer’s claims have already been analyzed here, and rejected. I can’t tell from the various popular news reports whether or not he’s added anything new that would affect the previously linked realclimate analysis. Regardless, the modern climate record contains very little variability that is not confidently explained by the forces outlined in articles like this . Several RealClimate articles spend at least a few paragraphs on this; see here, and here. Also, see my earlier post, if you’ll accept the arguments of this non-climatologist.
Re#47. Thank you, you are absolutely right. Sorry I have not had the conditions nor time to read all the articles and previous posts.
Of course I accept all arguments form people who are reasonable and cautious. No matter if they are or not climatologists. I am not.
Almost everything is important. For example, sometimes some chemical reactions cannot be reproduced because the initial obtained had a few molecules which acted as never recognized catalysts (unnoticed “dirt”).
I am sorry to comment things that have been already well discussed, because I also do not like when people makes comments over and over again about well discussed points. (example you point, 6.11.2.2 Cosmic rays and clouds, from http://www.grida.no/climate/ipcc_tar/wg1/212.htm )
I wanted to express it is overwhelming to deal with so many interpretations. I am aware too many variables are involved, and believe we are in a chaotic system. And, of course, it will never reach steady state. I can be always wrong.
Thank you again, regards,
G.
Hi grundt. Good to see your comments again & hope you are doing well. llewelly covered it aptly, but I like the link I provided in 28 above, as it is an interesting discussion that more should read. :o)
Best,
D
Hi,Dano. I am happy to talk to you again too!
Yes, yours is a good link. Mein Deutsch ist nicht gut.
But at least I can read the English links and translate some German text with help.
I have to take time to read it well. The cosmic rays subject was in the past (and is still now) very interesting to me.
Some physical and chemical reactions take place all the time due to these rays. Some reactors must be highly shielded due to their penetration . Very sensitive chemical reactions in labs are thought to have been influenced every now and then by them, leaving scientists without an easy explanation.
The last years events in my life made me lose so much information..
Thank you for your support, Dano,
Best regards,
G.