The Search for a Short Term Marker of Long Term Climate Sensitivity
By Dr. Roy Spencer. October 4th, 2009
[This is an update on research progress we have made into determining just how sensitive the climate system is to increasing atmospheric greenhouse gas concentrations.]
While published studies are beginning to suggest that net feedbacks in the climate system could be negative for year-to-year variations (e.g., our 2007 paper, and the new study by Lindzen and Choi, 2009), there remains the question of whether the same can be said of long-term climate sensitivity (and therefore, of the strength of future global warming).
Even if we find observational evidence of an insensitive climate system for year-to-year fluctuations in the climate system, it could be that the system’s long term response to more carbon dioxide is very sensitive. I’m not saying I believe that is the case – I don’t – but it is possible. This question of a potentially large difference in short-term and long-term responses of the climate system has been bothering me for many months.
Significantly, as far as I know, the climate modelers have not yet demonstrated that there is any short-term behavior in their models which is also a good predictor of how much global warming those models project for our future. It needs to be something we can measure, something we can test with real observations. Just because all of the models behave more-or-less like the real climate system does not mean the range of warming they produce encompasses the truth.
For instance, computing feedback parameters (a measure of how much the radiative balance of the Earth changes in response to a temperature change) would be the most obvious test. But I’ve diagnosed feedback parameters from 7- to 10-year subsets of the models’ long-term global warming simulations, and they have virtually no correlation with those models known long-term feedbacks. (I am quite sure I know the reason for this…which is the subject of our JGR paper now being revised…I just don’t know a good way around it).
But I refuse to give up searching. This is because the most important feedbacks in the climate system – clouds and water vapor – have inherently short time scales…minutes for individual clouds, to days or weeks for large regional cloud systems and changes in free-tropospheric water vapor. So, I still believe that there MUST be one or more short term “markers” of long term climate sensitivity.
Well, this past week I think I finally found one. I’m going to be a little evasive about exactly what that marker is because, in this case, the finding is too important to give away to another researcher who will beat me to publishing it (insert smiley here).
What I will say is that the marker ‘index’ is related to how the climate models behave during sudden warming events and the cooling that follows them. In the IPCC climate models, these warming/cooling events typically have time scales of several months, and are self-generated as ‘natural variability’ within the models. (I’m not concerned that I’ve given it away, since the marker is not obvious…as my associate Danny Braswell asked, “What made you think of that?”)
The following plot shows how this ‘mystery index’ is related to the net feedback parameters diagnosed in those 18 climate models by Forster and Taylor (2006). As can be seen, it explains 50% of the variance among the different models. The best I have been able to do up to this point is less than 10% explained variance, which for a sample size of 18 models might as well be zero.
Also plotted is the range of values of this index from 9 years of CERES satellite measurements computed in the same manner as with the models’ output. As can be seen, the satellite data support lower climate sensitivity (larger feedback parameter) than any of the climate models…but not nearly as low as the 6 Watts per sq. meter per degree found for tropical climate variations by us and others.
For a doubling of atmospheric carbon dioxide, the satellite measurements would correspond to about 1.6 to 2.0 deg. C of warming, compared to the 18 IPCC models’ range shown, which corresponds to warming of from about 2.0 to 4.2 deg. C.
The relatively short length of record of our best satellite data (9 years) appears to be the limiting factor in this analysis. The model results shown in the above figure come from 50 years of output from each of the 18 models, while the satellite range of results comes from only 9 years of CERES data (March 2000 through December 2008). The index needs to be computed from as many strong warming events as can be found, because the marker only emerges when a number of them are averaged together.
Despite this drawback, the finding of this short-term marker of long-term climate sensitivity is at least a step in the right direction. I will post progress on this issue as the evidence unfolds. Hopefully, more robust markers can be found that show even a stronger relationship to long-term warming in the models, and which will produce greater confidence when tested with relatively short periods of satellite data.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
To Bulldust and others:
Yes, I agree it is unsettling that I am using the climate models in the search for a marker, as if the models represent reality. But I do not know any other way to attack the problem.
-Roy
to Frank Lansner:
Yes, I agree that the NCEP reanalysis data going back to 1940 are intriguing. Actually, the reanalysis plots you refer to DO show an increase in total atmospheric water vapor (most of it is in the boundary layer, below about 900 mb, where it HAS increased)…but the fact that it has decreased above 700 mb is more important for water vapor feedback. If those data reflect reality, then water vapor feedback probably has been negative during the warming of the last 50 years.
-Roy
oMan (02:12:53) :
Anthony: your troll policy is remarkably enlightened. Another reason why this blog is so productive and congenial. Thanks.
Regarding the “mystery index” that shows 5x previous correlation with models– I humbly await further revelation. I imagine it’s a blend of things: “take 2 pinches of albedo, mix in 0.6 of average tropopause temperatures, allow to marinate overnight with average velocity of jetstream, subtract the square root of Michael Mann’s credibility, and serve hot.”
Can’t see the last term of this equation making much difference. A bit like the sprig of parsley on your fish dish.
Maybe it’ll be in a variation of the trade winds, the boundary between the tropics and the northern ocean gyres and the distributive westerlies.
=======================================
David Alan (00:57:53) :
I can’t wait for Dr. Spencers official unveiling of his secret marker.
Perhaps Piers Corbyn will beat him to it 🙂
I generally think it is a bad idea to conduct science by press releases or hints or teasers. If you got something, say it, or wait until you feel you can. In the computer industry there is the concept of Vaporware. This is Vaporware. Nobody is going to steal your marker and run with it to publish when it is clear that you announced it first. A blog can serve as a sounding board for new ideas [at least you might find many hostiles so you’ll learn how to deal with those]. But this way [giving us a teaser] does not serve that purpose.
I must have missed something along the way. Where might I find the Arctic ice measurements of “volume” I’m seeing so confidently referenced in some of these responses? We know “extent” from the satellite readings, but all I’ve seen on “thickness” has been a bit a core sampling here and there, a few U.S.Army buoy readings and the results of a radar skid recently flown over a swath of the ice.
In all cases of which I’m aware, the actual readings were reported as either “thicker than expected” or “thinner than expected”. The reason “expected” was the best the reporters could do was that there was no historical base of “thickness” against which to compare these readings.
The absence of an inventory of historic Arctic ice thickness renders any discussion of “volume” an exercise in speculation. Common sense would infer that cooling waters and cooling air should dictate “thickening” as well as “broadening”. However, even that inference can be thwarted by the truly determined with endless arguments about the behavior of “new ice versus old ice”, “clean ice versus dirty ice”, etc.
In the end, “There is none so blind as he who will not see.”
jon (04:47:10) :
RR Kampen: all of the ice that is in the Arctic today will be a year older and much thicker after this winter is over?
—
It might and it might all disappear next year and more, just like 2008 saw more than half of the multiyear ice from previous year disappear.
About two thirds of melting happens from below. Right now, even.
Peter Taylor (04:20:34) :
the work of Drew Shindell at NASA (I keep mentioning this but nobody seems to know what happened to the line of research) showed was correlated with a variable of solar output (UV light)
Shindell’s work was based on the obsolete Hoyt-Schatten TSI reconstruction and cannot be considered to be valid; perhaps that is why it is quiet around that line of research.
Maybe he’s looking for further pointers, as do you, Leif.
=================================
Hmmm. Water vapor feedback perhaps negative. I’ve long thought the water vapor feedback to CO2 forcing is variable, depending upon need. I base that thought on the long term stability of the system, its self-centeringness. But how, and why? Oh, my.
================
I’ve also wondered about the 800 year lag in the ice cores. First temperature rises, then CO2 rises, then at some later time, temperature falls, as does CO2. Is it possible the net effect of CO2 is cooling? Or at the very least, ameliorating warming? I know, the ice cores are not precise enough to say much about causation. But if water vapor feedback is some degree of negative, then the CO2 forcing it may also net negative.
==========================================
M. Kampen yet another RC TROLL. The Ice will not disappear all in one year unless we are struck by a major asteroid or the sun suddenly explodes. You simply have not grasped the volume of ice that makes up the Arctic. Remember that at the end of winter in the Arctic there will be around 15^106 sq:m of ice. In cubic terms I simply do not know and cannot calculate it because there are no known accurate figures for thickess but you could assume 2 m average. The energy required to melt that amount of ice would be as much as could be focused from the sun with a gigantic magnifying glass in space.
Mebbe height or latitude of the jet stream or both?
=========================
kim (05:12:51) :
Maybe he’s looking for further pointers, as do you, Leif.
At least I lay out my train of thought and what I’ve got. Not just just in blogs, but also at meetings and symposia where I ‘taste’ the waters before proceeding to publication [which in itself is just an archival process]
**********************
Claude Harvey (22:23:48) :
I suspect the “skeptic” community will not be delighted with Spencer’s eventual unveiling of his latest theory.
**********************
I don’t speak for all skeptics, but this one just wants the truth – no more and no less.
I took a quick look at the historical Atlantic HURDAT Storms–http://www.gfdl.noaa.gov/historical-atlantic-hurricane-and-tropical-storm-records. Much like Dr. Spencer’s graph a shift in 1938 takes place and around 1980. I wonder if one of the missing links in the climate puzzle is changes in the speed of the thermohaline circulation.
OT to main thread, but I cannot help “biting”.
Here’s three links showing thickening in our icy bits.
Arctic
Antarctic
Greenland
Bear in mind, accurate records have only started since 1979, a period that coincided with the warm phase of the PDO, elevated sunspot activity, and a whopper of an El Nino in 1998.
Anecdotal evidence e.g. Amundsen’s navigation of the North West passage, would suggest that Arctic sea ice extent has been the same or lower than the present, at various times in the past. How about we come back to a discussion in twenty years when the cold phase of the PDO runs it’s course?
Re: kim (05:19:27) :
“I’ve also wondered about the 800 year lag in the ice cores.”
—
First temperature rises due to long term Milankovitch (and such) effects. Vegetation and sea start releasing CO2 with a lag. This CO2 immediately helps to rise the temperature. From about a third of the climbing trajectory to interglacial maximum this CO2 becomes the dominant driver for further warming. The lag has then disappeared and temp and CO2 appear to rise simultaneously then – but in fact temp lags CO2 by a small time.
****************************
Bulldust (22:25:56) :
Have we got to the stage where science is now backwards? We generate models and feed in some data, then come up with an hypothesis? As someone that has studied econometric modelling extensively I find this somewhat disturbing, but perhaps I am getting the gist of this article wrong.
******************************
In a published paper, it referred to a computer model as an experiment. It isn’t. It is a simulation. It looks like some of the climate scientists have fogotten the scientific method.
I understand Leif’s position in Leif Svalgaard (05:08:51) but I’m not sure it applies to climate science. Look at Gavin’s behavior when McIntyre provided just a hint of the problems with Harry. He went off and studied it himself, found the problem and then took credit for the discovery.
I’m not sure you can extrapolate from other sciences to the highly politicized arena of climate sciences.
danappaloupe (00:20:54) :
The topic is covered in many, many other posts through the years. Why rehash it as an off-topic thread? If you accept Anthony’s offer of your own thread I will reply there on that and why or posts appear to be trolling (if not, then why were your posts about sea ice so blatantly wrong).
Roy Spencer,
Not to be overly critical but anytime you use models to try to explain one another vs real actions by the climate to expose a climate variation marker ( which from your article appears to be what you are saying ) is perhaps not the best idea in the world.
In other words the climate models have more then likely too many assumptions built into them. I don’t know since I do not have their code ( is the code actually published someplace?) I have built more then my share of models ( I call them simulations since they do not technically model what will happen but simulate what could happen ) on various subjects. The one thing I have found is that there is an immense amount of complexity even with a seemingly simple simulation.
However I do know this much. IF CO2 is assumed to increase temperature in a simulation… it will. No matter what variables you then feed it. So sorry if I sound slightly skeptical about the marker you have uncovered but… well again I may have misunderstood what your post is about. If so forgive my lecture on models and my feeling about the climate ones at this point.
I must also state that I do not make hugely complex models as a form of living, rather I make models to understand the data that I have and try to figure out efficiencies that can be gained by changing variables or introducing new variables to the system. I must also state that real life does not always mimic my results. Hence my skepticism of any model ( simulation ), whether I write it or someone else does. Though I am sure other peoples simulations are always spot on when compared to real life.
“WUWT won this year’s “Best Science” category in the Weblog Awards. Click on their icon on the upper right of the page. Compare the results to RealClimate. ~dbs, mod.]”
I did just that, hadn’t before, and it was very informative. I had never heard of the site that got the second highest vote total (I won’t name names, interested people can find out for themselves) so I looked to see what it was about. I was quite surprised to find that (at least at this time) it had articles about meetings and parties, favorite wines, people they didn’t like, and t-shirt sales, but not a *single* article currently on the site that was actually about Science.
I had really hoped for something more. Disapointing, but a further confirmation that WUWT stands head and shoulders above all of its competitors as the place where REAL science is discussed.
The AGW true believers are hoping that by moving the goal posts, from ice extent to volume, they can distract people from the fact that
1 – ice volume was never an issue in earlier years
2- that measuring ice volume is very dubious
3- that ice volume is irrelevant to floating ice.
The AGW hysteria was always about ice pack extent, until ice pack extent began to grow. This is typical AGW community behavior, as we have seen regarding sea levels, temperatures, tropical cyclones, etc.
The Arctic ice pack acts to insulate the water and reflect sunlight.
But this is not about ice. It is about AGW true believer’s inability to deal with inconvenient facts.
They attack a man of proven integrity, like Dr. Spencer, by mixing his religious beliefs with his science, and ignorantly judging both.
No one who is a serious student of science is ever going to conclude that being a theist disqualifies someone from being a scientist.
Dr. Spencer ahs proven himself over many decades to be a capable ethical scientist, operating transparently and with integrity. As contrasted to, say, Briffa, Hansen, Schmidt, Mann, et al.
Might this mystery marker be analogous to something in the disruption/recovery cycle found in natural ecosystems? E.g., when a hurricane blows through a forest and it takes a while for the biota to recover to previous levels of productivity.