Jerks
Eli was wandering through AGU when he came across a poster which insisted that all climate change is just a collection of jerks. This has now, in more impenetrable form (according to the author) been accepted for publication in JGR, and you know what editors are. Roger Jones proposes that continuum models just do not fit the data at all scales and intervals, that stuff changes suddenly.
Past climate change has often been rapid. Although future climate change could also be rapid, it is usually communicated as a trend.Jones has looked at a number of changes, including air and sea temperatures at local to global scales, precipitation, and more.
Climate projections developed from coupled atmospheric ocean models are interpreted through a signal to noise model. This model interprets the anthropogenic signal in climate variable (temperature, rainfall, etc.) as a smooth curve and variability as noise around that curve..
For long time series of annual data, annual to decadal variability is interpreted as being of natural origin.
Were these changes natural variability superimposed on a long term trend or were they a non-linear response to anthropogenic forcing
The resulting investigation has concluded that anthropogenic climate change is a non-linear process. Rather than following the signal-to-noise model, climate change follows a step and trend process.
The bunnies thought about this, and the useful analogy is earthquakes. Stress (e.g. forcing) builds steadily, but change happens suddenly. Averaging, smooths change to a fair-thee-well, continuum models do the same. The uncertainty monster is not anyone's friend.
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32 comments:
Perhaps unfortunately, jerk, or surge, is an engineering term for the rate of change of acceleration.
Much about climate (certainly not all) can be considered to be Navier-Stokes writ large. With turbulence various forms of non-linearities abound. The problem lies not so much with continuum mechanics but our inability to solve any but the simplest of equations.
Like the car brakes they work fine, they wear but they work fine, they wear and wear and no problems then one day it turns out your mechanic was right you should have fixed them a month earlier.
It would seem there are similarities in the climate, absorbed heat little change, absorbed heat little change, absorbed heat big change. The paleo record is full of sudden responses after a period of little change; Like the meltwater pulses.
This Doomsaying Little Mouse has said it elsewhere. When you consider the very gentle nature of the Malinkovich cycles and the massive climatic response; compared the huge change in forcing we are doing should we not expect a big response. It seems that we know how fast a candle melts the icebox and expect a blowtorch to melt it at the same pace.
As everyone, even the physically fit deniers, though they fly aeroplanes, agree Navier-Stokes is practically impossible to solve on the global scale, why such abhorrence towards the statistical treatment of the boundaries present in a system? (A poorly formulated question and if that made some sense, it's partly by luck)
It seems to me the Hadley Cell is partly constrained by the tilt of the earth's axis, as well as the Polar Cells (i.e. if the tilt was 45 deg., there would not be any Ferrel cells.) But still, why do Ferrel Cells exist? I've not seen a good explanation of that. What would f.e. happen in a climate model if there wasn't Andies and Rockies disturbing the aerial flow of water vapor (i.e. would the swings of weather patterns be larger under the Ferrel Cell in such a topography)? I mean, if there's an energy overdose on Troposphere, Hadley Cells would expand and similarly for 'underdose' and Polar Cells. Given the Northern Polar cell almost has to have a high pressure at sea level in winters (southern also in summer for the ice sheets present) for the lack of solar heating, wouldn't this mean that once the ice is gone in summer, the NH weather patterns would experience a more dramatic change than the SH in periods of rapid climate change, and that these changes would be more dramatic during summers? In another words, does the Arctic Amplification spill over (yes it will) under the Ferrell cells in some boundary conditions and what these are? Is the frequency and areal extent of blocking events incresing periodically in NH which would lead to a step-change look-a-like patterns of warming under the NH Ferrell cell?
Bah, now the previous looks a bit like pseudo-scientific babble, better to put in some science too. I guess plenty of the things in lectures on fossil fuels are familiar for most of the readers here already:
http://www.youtube.com/watch?v=3cHC1H-K4Is&feature=BFa&list=SPFA75A0DDB89ACCD7&lf=list_related and the next one in the series.
sub-arctic bunny (who should likely learn how to be more coherent)
Sorry, still continuing the babble: The trouble with treating the climate response as step-change process is that there's no way of knowing how big the next step will be. The discontinuum introduced might have some physical analogy (say, an unusual breakage of the Polar Vortex) on some temporal scales, but on other scales not. So if there was a step-change function in a model this would have to be specified by the temporal resolution of the model. This might even be easier than treating various processes as having an exponential response but would likely not help in predicting the time of occurrence of such a change (say, expansive permafrost meltdown).
Hmph, now likely sounding a bit like an alarmist, maybe it's time to write an 'official scare thread' on the blog.
sub-arctic bunny
sub-arctic bunny,
unpredictable perhaps, but I think there is a set of physical mechanisms driving these changes that can be better understood. The ocean is the hot-tub driving the atmosphere.
If you're planning adaptation, which is better? To move by regular adjustments and cope with the noise as suggested by the signal-to-noise model, or to plan on step changes at an undetermined time by adopting flexible, resilient methods that can adjust quickly as soon the shift is recognised. Which is why the mechanisms are important to understand. ("Jerks" in regional temp can be in the vicinity of 0.5C to 1C, even higher in model simulations of the mid 21st century).
The knowledge might not be pleasant (it could even be inconvenient), but it does affect how one plans for rapid changes in extremes like heat, fires etc.
I don't know why people find comfort in uncertainty.
Anon(1)
oh, the author himself...
Dr. Roger Jones, I didn't mean to say your approach on this issue of step-change was somehow irrelevant, rather as step changes are commonly used by deniers who somehow think a step-change under an increasing CO2 forcing could go more down- than upwards in the temperature scale (that is the enegy-level of the sub-stratospheric earth inceases), it somehow convoluted to the extensive babble of various phenomena in the atmosphere I'd like to know more...
As the governement systems of most countries are made real by laws, and instigating a law represents a step-change in the anthropogenic environment I'd say mitigation and adaptation necessarily is done by step-changes, say if I'd put more insulation on the house it can be looked as a step-change in winter heating costs (though on current climate scenarios they'll come down anyway...). The approach could be useful in planning energy policies, yes.
sub-arctic bunny (M.Sc. who isn't so sure about his maths)
'instigating' should be 'instituting', sorry, not my native language.
Some ill-informed comments before reading the paper: by appearance, this is reminiscent of some graphics that sceptics make from time to time, through which they try to claim that the observed history is a series of magical step changes related to ENSO or whatever else.
But, I admit that I don't understand what the contribution here is, so I'll wander off and read the paper.
sub-arc bun - I wasn't having a go at you or being defensive. The question I asked is genuine and I'm really interested to see what people's responses are. You're right about policy being non-linear.
My real interest in making "good" decisions under conditions of uncertainty. It's a fascinating psychology in many who would prefer a "predictable" answer that we know is wrong to an unpredictable one that is correct but doesn't give the comfort of certainty.
Anon(1) - uncertainty is opportunity for scientists - something to be explored. Most people don't feel that way, for sure. But in complex systems it can't be reduced by methods of linear prediction. Uncertainty can be managed by acting and mismanaged, too. Let's not pretend the world isn't what it is, because that's the first step on the road to mismanagement.
I was thinking of various skeptics out there who say that because there is uncertainty, there is no need to act, or that we cannot act. Much of science exists on the edge of uncertainty, but strives to tell us what is the more likely explanation for that which is uncertain.
Anon(1).
Anon(1) - yep. Clarified your earlier comment
sab and ce, the point to Eli was the build up of stress in the system followed by sudden release. Very similar to what happens in mechanical systems such as earthquakes and stuck gears (so yes, the pun is multilevel and approaches, if not encompasses completely the idea of mechanical jerk as db pointed out.) This is a modality which adds to Hanson's pointing out that there are unpleasant surprises lurking in the deep, where heat is building.
Since the stress is all in one direction the jerk has to occur in that direction which is the difference here between the jerks' jerk and the Jones jerk.
Living in south eastern Australia, I'm very interested in this study. (Hope you can make a copy available at some stage, Roger.)
Having left the region for some time and then returned early in the 2000s, the step change seems very noticeable just using the old unreliable memory. For example, using the blanket test - in the 1950s and 60s you could count the number of times each summer when it was too hot for a blanket at night in summer. This past decade you could count the number of times it's cool enough for a blanket at night in summer. (This current summer has been very pleasant and could well be one of the last mild summers.)
The next step change could be very tough. We've had more and bigger fires in the past ten years than in the previous sixty (at least) combined, and record heat and heat waves. Several years of drought followed by record precipitation events and floods last summer.
I'm not sure how inland areas are going to be able to plan for water in the next drought. A bit far from the sea to desalinate, and the mountains are a barrier even if it was seen to be worth the cost.
Fire fighting is a problem too, with it getting harder to keep volunteers - especially for the large fires that last for several weeks. We'll need to rethink a lot of the old systems that aren't suited to today's demographics.
Dr. Jay Cadbury, phd.
"The bunnies thought about this, and the useful analogy is earthquakes. Stress (e.g. forcing) builds steadily, but change happens suddenly. Averaging, smooths change to a fair-thee-well, continuum models do the same. The uncertainty monster is not anyone's friend."
Change is not going to happen suddenly when the earth is below GAT and below average levels of atmospheric co2. In this case, the uncertainty monster is our friend because we are below average historic levels.
Well, we've known for a while that climate trends are non-linear. But what does the step-and-trend model say about what will happen over the next century that the linear trend model doesn't? Aren't they both going to arrive at roughly the same end points? Does a step model make better decadal predictions along the way than a linear model with some kind of modeled random variability thrown in?
Also, I notice that the biggest "step" in the Ocean Heat Content data is in the early 2000s. I thought that large jump was due to a changeover of instruments, from XBT probes to Argo floats, or am I confused?
-Wheels
Dr Jay:
I live in Southern California, and I noted that the chandelier was unusually stable, due to the absence of moving trucks driving by. I am happy to report no earthquakes due in 2012!
Dynamic feedback systems, such as our weather, often have an infinite number of states, of which only a few are stable. Force a dynamic system out of one stable state and it will rapidly seek another stable state.
None of the climate models recognize the very powerful, but very localized carbon feedback mechanisms in the Arctic. Thus, the climate models do not recognize the full rate at which the weather system can seek a new state.
The concept of "Climate" is dead. We have today's weather. We can no longer look back on previous weather to estimate future weather. We can expect future weather to be more extreme than past weather, not just sometimes, but as a normal characteristic of the weather. The new reality of climate is that future weather will be different from any weather we expect from experience. (At least until we stop putting stuff in the air, and the weather system finds a new stable state.)
Eli,
Well, yes, those mechanical systems act that way, but so what? We need a physical mechanism for why climate might act that way.
I wouldn't be surprised if you could sit there and convince yourself that you see such a pattern in synthetic data created as trend + high amplitude noise. Could be fun to do. But I still have to read the paper. Here I am making a second comment without having done that - I should be sent to bed without my carrots.
Aaron --- I doubt a suitably narrow stability exists, especially after studying Ray Pierrehumbert's "Principles of Planetary Climate".
This is an apposite post.
Elsewhere I have been trying to nail a recalcitrant denier to commit to a specific value for climate sensitivity, and it occurred to me that too many folk seem to automatically assume that an overall encompassing value for sensitivity will remain constant over a range of changing planetary temperatures.
This is obviously unlikely to be the case, and I'm wondering if perhaps it is counterproductive to focus on a single value in discussions of such...
Thoughts?
Bernard J. Hyphen-Anonymous XVII, Esq.
(Word verification says 'eighti')
Bernard, I agree with you. That doesn't count for anything, because I don't have relevant expertise, but I've been wondering about various feedbacks (positive and negative) coming into play at different temperature levels. However, this will be smoothed, over the globe, as the various regions will act to buffer each other slightly. I can imagine step-changes though, as a sizable region transitions from one climate state to another (say, loss of arctic permafrost, or the transition from prairie to desert. Mind, water vapour feedback will be relatively constant across these regimes, and that's the largest contributor.
"Dr." "Jay" "Cadbury" "phd" (since you've acknowledged none of these things are true). Tell me about the agricultural productivity during those 'historic' periods when CO2 and global temperatures were higher. 'Historic' generally means during the period of written history. I don't recall any written records from 20 million years ago.
Dr. stewart, Ph.D.
Dr. Jay Cadbury, phd.
@Dr. Stewart
"Historic' generally means during the period of written history. I don't recall any written records from 20 million years ago."
this could be a problem because I was going to suggest you look at a picture of a plant in the Cambrian period when co2 levels were around 7,000ppm.
Furthermore, there was an ice age during the Ordovician period when atmospheric co2 concentrations were 4400ppm. Of course here at rabett run, revisionist history is practiced and this has been stricken from the record.
So you see Dr. Stewart, when I ask Eli a good question about something like this and get called a denier, I happen to think the global warming scientists knowledge is severely lacking. Global warming has become the new neo puritanism.
Funny old chocolate nutbar (or is it fruit and nut) said:
"Furthermore, there was an ice age during the Ordovician period when atmospheric co2 concentrations were 4400ppm. Of course here at rabett run, revisionist history is practiced and this has been stricken from the record."
Too bad he didn't do a little bit of checking since he would have found that he is completely wrong. Here is what the science actually says about Ordovician ice ages, noting that solar output was considerably less than now:
"Past studies on the Ordovician period calculated CO2 levels at 10 million year intervals. The problem with such coarse data sampling is the Ordovician ice age lasted only half a million years. To fill in the gaps, a 2009 study examined strontium isotopes in the sediment record (Young 2009). Strontium is produced by rock weathering, the process that removes CO2 from the air. Consequently, the ratio of strontium isotopes can be used to determine how quickly rock weathering removed CO2 from the atmosphere in the past. Using strontium levels, Young determined that during the late Ordovician, rock weathering was at high levels while volcanic activity, which adds CO2 to the atmosphere, dropped. This led to CO2 levels falling below 3000 parts per million which was low enough to initiate glaciation - the growing of ice sheets".
http://www.skepticalscience.com/CO2-was-higher-in-late-Ordovician.htm
"a picture of a plant in the Cambrian period when co2 levels were around 7,000ppm. "
Grass during the Cambrian? That's the kind you need for agriculture, as Dr. Stewart was being specific to.
DJCad,
"there was an ice age during the Ordovician period when atmospheric co2 concentrations were 4400ppm."
Nope. There was a continental ice sheet at the south pole. That's not an 'ice age.' But what relevance does the Ordovician have for today? Utterly different continental configuration and oceanic circulation, large areas of warm shallow seas resulting in massive carbonate banks, and, perhaps most importantly, lower solar output. Your point is an empty one.
I've added a post on what happens when you look at changing extremes.
CE, the paper doesn't have the physical mechanism, but that is being worked on. Have narrowed it down quite a bit.
Sou, the paper will be public domain when it comes out. Or people can email me and I can send the in press version. fname.sname at vu.edu.au
"Change is not going to happen suddenly when the earth is below GAT and below average levels of atmospheric co2."
How is it that the last ice ages developed slowly, with Dansgaard-Oeschger events during the glacial period, which have abrupt warming over a few decades followed by century scale cooling; and end more quickly, with changes(temperature, Greenland snowfall, dust accumulation) in the Bølling-Allerød event occurring in less than a decade?
Brian Dodge --- Those are all arctic effects (or least far north effects). Not global and don't even show up in Antarctic ice cores.
@ David B. Benson
Roger Jones shows by data(mostly - some model) analysis that an ensemble of step(nonlinear) changes are a better fit than trend plus noise to our shifting climate. Eli Rabbet points out that this is analogous to earthquake behavior, where the uncertainty of stick-slip behavior and sudden change increases risk(as well as the granularity of effects). The uncertainty monster seen through the filter of a noisy continuum model, average smoothing filter looks a lot less scary than he actually is up close and nonlinear. (I'll refer to this combination of Roger Jones & Eli Rabbett's work as Roger Rabbett risk analysis &;>)
Dr. Jay Cadbury, phd. argues that because current temperatures and CO2 are below average, rapid changes can't happen - demonstrably false -, and concludes that this makes the uncertainty monster is our friend.
Your assertion that the sudden climate changes seen in the Greenland ice cores are only local(the dust changes aren't, BTW) implies that nonlinear climate change lurching toward an uncertain future, like earthquakes, aren't hazardous because spacially averaged, the effects are small; but the 2011 Tohoku M9.0 megathrust earthquake was only ~50 km of an ~850 km subduction zone, which is in turn only a tiny fraction of the "ring of fire". Agriculture is inextricably bound to climate, and since the world only has a ~2.6 month supply of grain in storage, weather as well. The US exports 52% of the corn, 44% of the soybeans, 27% of the wheat, and 11 % of the rice in world trade - using 0.00001% of the world croplands; if the 0.00001% of the world that is experiencing drought, or flooding, or earthquake happens to be the 0.00001% critically located for catastrophic risk, the cost will be very high.
Uncertainty precludes our being able to accurately estimate the probabilities, and nonlinearity magnifies the consequences - likelihood X cost = risk. The 1964 Alaska M9.2 megathrust earthquake killed <300 people and cause about $2.1 billion (2009)dollars in damage; the 1960 Valdivia Chile M9.5 megathrust earthquake killed ~ 6000 people and cost ~$6 billion (2011) [high uncertainty].
The 2011 Tohoku Japan M9.0 megathrust earthquake killed ~13800 people, and cost $235 billion (2011?)dollars in damage, more than 5 times the deaths and 50 times the cost one would guess based on a simple average of previous events. Black swans dominate risk, and the uncertainty monster is a friend to them, not us.
You can see over at Tamino's the fulfillment of why I'm sceptical of people seeing steps and jerks in these histories.
But I still haven't read the paper.
> sceptical of people seeing steps and jerks
Oh, I believe people _see_ them.
Lots more than are.
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