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gws at 02:19 AM on 11 October 2012Climate time lag
continued Multiply the above picture with the actual TSI impact (aka smaller 1 W/m2) and you understand why the TSI impact is so small. What about CO2? I created a simple model of atmopheric CO2 concentrations (from 280 to roughly 395 ppm) following an exponential increase with constantly increasing growth rate (see, e.g., Tans et al., Atmos. Environ. 43(12), 2009); not exact, but an ok first guess. I then used the Myhre formula (forcing = 5.35*ln(C/C0), which gives a 3 K climate sensitivity for doubling CO2, and a 1.7 W/m2 value for the 395 ppm end point) to calculate the changes in forcing over time, then repeated the incremental integration as above. For comparison purposes to TSI, I further assumed that the atmospheric CO2 increase suddenly stopped at 400 ppm. The resulting graph looks like this:
Note, again, that the T increase is in lock-step with the driver increase (here: [CO2]) as long as the increase is maintained, thus a close correlation between CO2 and T is expected as long as only CO2 is driving the system. But note that in this case, much more warming is in the system, with "only" 0.7 K realized by the time the CO2 forcing stops, with another 0.5-0.6 K in the "pipeline".
Not bad for a simple box model I would say. I was suprised myself. I will supply the R code for this to the moderator, or post it here if desired.
One other thing:
The difference in physical forcing between TSI and CO2 is one of wavelength: In the case of TSI increase, most of the extra incoming energy is in the form of shortwave radiation. In the case of GHGs, it is in the form of long-wave radiation (infrared). So while GHGs "dump heat" efficiently into the system, TSI increases drive a number of other things as well, e.g. chemistry.
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gws at 01:59 AM on 11 October 2012Climate time lag
Falkenherz Hmmh, you are smart but you decline to look into the math ... so ok, I did the math for you, or better say, for your thought experiment: We start with the assumption that the system does have a lagged response between 25 and 50 years. If a perturbation (energy imbalance, I, in energy per time) to it occurs, the response is converted with a rate k (=1/tau) into a temperature, T, increase proportional to the difference in T between the equilibrium response and the current temperature, aka dT/dt = k*(I*cs - T(t)) (eq. 1) with cs = climate sensitivity in K per energy (assumed to be ~0.7 K per W/m2 as in Hansen et al., 2005), and k in per time (so that tau is in time units, say yr^-1) The solution to this (separable) differential equation is T(t) = I*cs *(1-exp(-t/tau)) Let's assume first that we have an instantaneous input of I to the system, a step change so to say. This was explained hetre before in numerous words, and by Riccardo with a graph. The first graph I produced here is the same basically:
It shows the response to the step change for various lag times from 25 to 50 years (in 5 year steps plotted in black to cyan).
Note that I alinged the year axis roughly in assumption that the increase occurred in 1750. Let's say this is the hypothetical TSI increase of 1 W/m2, so I am actually strongly overestimating its potential effect on Earth's T.
So this is for illustration on how the lag works.
Next, let's make it a bit more realistic:
The TSI increase could be assumed to be linear (based on your comments) instead of step-change like. So I had it linearly increase from 0 to 1 and then stop (as per your comment again).
The differential of that curve gives me the yearly increase in TSI, each year inputing a bit of energy to the system, which can be modelled exactly teh same way as for teh step change illustrated in the above graph. One then needs to simply add up all those changes (integration). The resulting change in T looks like this:
Note that (a) during much of the linear TSI increase, T also increases linearly, hence the close, near linear correlation between TSI and T during the phase of change, and (b) once the forcing is shut off, an exponential decay of the remaining T-increase results. As you can see though, much of the increase had already happened at the time the forcing was shut off (0.5-0.6 of the equilibrium 0.7 K, depending on lag).
(more to come)
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Bob Loblaw at 01:55 AM on 11 October 2012Climate time lag
Falkenherz: ""climate lag is the same for all forcings but it is not the same for all forcings" (hi, bob) " What I specifically said above in #356 was "and the TSI increase vs. CO2 increase effects are, to a first approximation, not much different", and I followed that in #369 with "different radiative forcings can have different effects, although many of the differences are subtle." Note the "first approximation", and "not much different" in the first quote, and the "many of the differences are subtle" in the second. If you seem to think that I claimed that "climate lag is the same for all forcings", then you you aren't reading well (or aren't understanding well). If you seem to think that my two statements are in disagreement, then please be explicit is saying how. I'm going to try to rephrase what I (and others have) said earlier. Concepts such as "time lag" are very simple ways of trying to understand one aspect of a system. Although such simple constructs may provide a useful way of visualizing one or a few characteristics, the simple constructs will fail to catch many of the details. Trying to force the details into that simple construct will undoubtedly fail. "It is still not clear to me why an existing climate lag cannot be visualized by displacing cause (TSI) and effect (global temp) accordingly on the time axis." For starters, there isn't a single "existing climate lag". Secondly, what are you trying to show by doing this? The appearance is that you are trying to force observations of the real world to fit a simple model - one that is too simple. As DSL points out, to do it well, you have to start out including other factors. I gave a list in #369 of all (or close to all) of the things that would need to be considered to get a full understanding of the climate system. Depending on the purpose, models can leave some of those things out - but still be useful. Leave the wrong ones out (for a specific purpose), and you'll end up with a bad model. Remember the old saying "as simple as possible, but no simpler". By focusing on a single time lag concept, you are going too far past the "no simpler" point. -
Composer99 at 01:42 AM on 11 October 20122012 SkS Weekly Digest #40
With regards to the 'What Say You?' portion of this post: What spoonfuls of sugar do we have in our arsenal that might enable the average person to swallow the "medicine" of climate change mitigation and adaption? I might suggest that babies are a particuarly poignant spoonful. From the evidence, we can be reasonably confident that climate change and ocean acidification is already disrupting present-day food production and will eventually cause severe disruptions in global food production. I personally would go so far as to say that we are at, or near, the point of choosing between the mutually exclusive options of a carbon-based society today or reliable global food production tomorrow (metaphorically speaking). Suffice it to say, small children across the world alive today are the ones who are, at present, going to feel the worst of the climate disruptions to come (to say nothing of their descendents). I have a one-year old son, and the thought of him not having the opportunities afforded to me and my generation due to ongoing climate disruption is not a pleasant one. Suffice to say I do not find appeals to emotion, or appeals to consider the interests of future generations, illegitimate, as long as they are based on a solid foundation of evidence & logic. -
DSL at 01:21 AM on 11 October 2012Climate time lag
Falkenherz: "It is still not clear to me why an existing climate lag cannot be visualized by displacing cause (TSI) and effect (global temp) accordingly on the time axis." Who says it can't? However, if you're going to do it well, then you need to isolate the solar signal in the temp series. You need to strip out GHG forcing, aerosols, ENSO, etc., to reveal the solar effect on temp as purely as possible, and then you can go lag hunting. Even then, it's going to be tough, because the effect isn't going to return 100% at one point in time. General circulation is going to spread out the return. The spread may be consistent, but it still confuses the issue. -
Falkenherz at 01:02 AM on 11 October 2012Climate time lag
Dear all, thanks for your last comments, but I think most are by now besides my point. I have the impression you sometimes read only half of my arguments and jump on some red flags; answers range from "you have no idea so shut up and read" to "climate lag is the same for all forcings but it is not the same for all forcings" (hi, bob) to "it is too complicated to give a simple answer" to "you cannot do this". (-snip-) I need to be able to understand answers with my limited non-scientific perspective. Especially the link to the discussion of Shapiro et al. offers interesting insight for me. It is still not clear to me why an existing climate lag cannot be visualized by displacing cause (TSI) and effect (global temp) accordingly on the time axis. If I roughly understand the results and the discussion under the "Shapiro article", I should confirm nothing else than what we found out here, anyways: The current rise of global temp is simply too much to be even a concealed trailing off from a raised TSI-end-level from 1960.Moderator Response: [DB] Tone-trolling snipped. -
jyyh at 23:59 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
the gravitational pull effect occurs likely with Antarctica too, so what does that do for sea levels in NH? -
chriskoz at 23:31 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
Rob@4, Yeah, let's say that: Jerry did not draw the complete picture of SL in last 10ka but suggested it would be a hockey stick shape with a blade angle 1.5-2mm/y in XX century and accellerating to 3.5mm/y in satelite era. So there is no doubt which paleo guy from PSU you are talking about. It's so obvious that I don't even think about it, and I'm not even sure if SLR hockey stick can be technically compared with the original from tree rings but the PSU guy deserves every piece of credit, so let's add SLR hockey stick to his "league". -
chriskoz at 23:11 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
Jerry does explain the SLR variability maily with icesheet gravitational pull. He shows the map (at 16:10) of modelled GIA melt that explain the "European problem". He mentions the isostatic rebound be also a part of that map, but does not explain the relative impact of ISR vs. gravitational pull. We know that i.e. Scandinavian Peninsula is affected by ISR. Further, I don't see ISA from Laurentide Sheet on Jerry's map. In particular the sinking of the East US coast is not visible at all. I would like to know at least the ballpark figure how those two effects relate: which one is larger at the current SLR rate. Anyone knows? -
Icarus at 22:39 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
Very interesting lecture - thanks for the link. I thought: Maybe they can use the geographical fingerprint to add useful data to our understanding of ice mass melt over time (e.g. maybe the tide gauge data would show that Greenland started to melt before the WAIS)... but wouldn't that be confounded if there was also non-uniform warming of the oceans? Given that a component of sea level rise is thermosteric (I hope that's the right word), presumably some parts of the world's oceans are warming faster than others and therefore contributing more to sea level rise in those regions. If the portion due to ice melt was not geographically uniform then that would be another complication to have to take into account, and might limit the usefulness of the 'fingerprints'. -
Daniel Bailey at 22:37 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
anja247, isostatic rebound is a slow process. Here in North America crustal rocks are still rebounding from the demise of the Laurentide Ice Sheet and its associated overburden more than 10,0000 years ago. Expect SLR on the decadal-to-millennial timescale with crustal rebound lasting for many, many millennia more until a new equilibria is reached. -
anja247 at 22:28 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
that was a truly fascinating lecture! i was left wondering about the duration of the 'european problem': when the ice on greenland melts the gravitational pull diminishes, and adjacent sea levels drop... i understand that mechanism, it makes perfect sense. but, once the weight of the ice sheet on greenland disappears, wouldn't this cause greenland to rise, and won't the gravitational pull then be re-established? and would that not affect sea level in the northern hemisphere (increase)? -
Kevin C at 21:05 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
batsvensson@1: If I understand correctly you are right. Using tide gauges we need to track local sea levels, because only by tracking local changes and the reconstructing the global change from the fingerprints can you get an accurate picture of the volume of water in the oceans (which is what changes when ice melts). I presume satellites give a more direct indication of volume. For any future ice melt, you need to project where the ice will melt and then apply the corresponding fingerprints to gain an estimate of local sea level rise. Global sea level rise is a useful metric to give a big picture, but doesn't tell you what will happen locally. Rob's excellent 'Sea level Isn't Level' series goes into more detail on this. -
skymccain at 20:43 PM on 10 October 2012New research from last week 40/2012
Thanks Ari for pulling all this together in one place. I really value this one-stop source as it obviously allows me more time to read, copy and file those studies on topics that I try to follow and seek to better understand. -
AndrewDoddsUk at 19:33 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
Global sea level is very much of interest.. From geological records, sea level rises of meters per century (max between 3 and 10m) are established; however these were in response to considerably slower warming. My impression is that both the WAIS and southern portion of the GIS are effectively unstable right now - as in, if we stablised CO2 concentrations at current values they would probably vanish over time. The only real question is how fast this can happen. So far the answer seems to be 'not catastrophic', but there again that's what we thought about the sea ice last decade.. -
skywatcher at 18:06 PM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
Rob #4 (and #3 William) glad you mentioned that, was at Franz and Fox last year and it seemed pretty clear to this geomorphologist that they were both decidedly retreating. The information board at Sentinel Rock was IMHO out of date. Very soon, Franz won't actually be visible from the famous Peter's Pool too. Lionel A, well said indeed. Most of the clowns that claim various egregiously wrong things about the climate have no concept whatsoever about the efforts, hazards and challenges involved in collecting field data from remote and often hostile environments. -
Rob Painting at 17:35 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
"So what do we conclude from this?" Actually, I'm very surprised that no commenter has noticed that these observations scuttle a well-worn contrarian myth. They very broadly support the conclusions of a very well-known paleoclimatologist from Penn State University. -
John Brookes at 16:01 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
Nice video, thanks! -
batsvensson at 13:51 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
Interestingly enough according to the presentation0 there is a positive 2nd derivative in the past two decades for sea level rise and that make me wonder what the explanation for this is? -
batsvensson at 13:39 PM on 10 October 2012Jerry Mitrovica: Current Sea Level Rise is Anomalous. We've Seen Nothing Like it for the Last 10,000 Years
So what do we conclude from this? Is global see level of less interest and what we instead should keep track of is the local sea levels? -
Climate time lag
Falkenherz - "...TSI changes will affect all other forcings, but no other forcing will affect TSI..." To clarify my previous comment: GHG's, volcanic aerosols, and ENSO are not driven by TSI changes. Anthropogenic GHG's are driven by our economic decisions, volcanism by geology, and ENSO by it's own aperiodic variations. The baseline TSI is quite stable; changes in TSI are only a fraction of a percent in value. And those TSI forcing changes are very small in comparison to GHG forcing changes - an order of magnitude smaller:
[Source]
I suggest you follow the evidence.
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Daniel Bailey at 10:26 AM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
Phil, you doing a Dr. Evil thing? Monocle too? And here I thought that I was the only one who did that... -
scaddenp at 10:16 AM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
"he is a Viscount, no less, so he should know." splorff! Now I have coffee in my keyboard and scratches from the cat. -
noelfuller at 09:49 AM on 10 October 2012New research from last week 40/2012
mike There are vaious forms of dry rice farming that overcome issues of CH4, water availability and high labour input at the expense of increased risk from weeds and pests but there is organic dry rice farming too. Rice is grown from seed directly instead of planting out seedlings. Also check out aeroponic rice farming. You have to give google a nudge here as it defaults to hydroponics. Noel -
vrooomie at 09:28 AM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
"...this video...conflicts with what Lord Monckton says..." Yes; reality and facts are often at odds with the good Viscount. Fortunately, it's easy to figure out where reality ends and Monckton's Myths begin... The deniers really are going to look (even more) *really* idiotic, and sooner rather than later will be fine by me. One can only argue against empirical data for so long. -
Bob Loblaw at 08:06 AM on 10 October 2012Climate time lag
Falkenherz: To update: different radiative forcings can have different effects, although many of the differences are subtle. Different parts of the system have different response times. Different parts of the system have different energy flows and circulations that must be accounted for. You seem to be in search of simple explanations for components of the system, and then when you get them you seem to want to mix and match those simple explanations while keeping them simple. This is not working, because the simple illustrations all leave something out - so that they can be simple. Here is what you need to do: - look at incoming solar radiation at the top of the atmosphere, including daily, seasonal, and decadal variation. Don't forget to include spatial distribution ("geography"). - look at the changes in solar radiation as it passes through the atmosphere. Don't forget to include the effects of normal air molecules, trace gases, particulates, aerosols, absorption, and scattering. Don't forget to include daily, seasonal, and decade variation, and spatial distribution. - look at IR radiation in the atmosphere - both emission and absorption. Don't forget to include daily, seasonal, and decade variation, and spatial distribution. - look at surface absorption and emission of radiation. Don't forget to include daily, seasonal, and decade variation, and spatial distribution. - look at other energy flows: thermal energy, evaporation, condensation ("latent heat"), etc. Include the atmosphere, earth, and oceans. Don't forget to include daily, seasonal, and decade variation, and spatial distribution. - look at stores of energy - oceans, earth, atmosphere, and the exchanges between them. Don't forget to include daily, seasonal, and decade variation, and spatial distribution. - look at the physical circulation patterns of the atmosphere and oceans,and how the pressure distributions and circulation are linked to the energy flows. Don't forget to include daily, seasonal, and decade variation, and spatial distribution. If you search carefully, you may find that someone else has already done this. They will have taken a description of the earth/atmosphere/ocean system with realistic geography, included circulation mechanisms and energy transfers and storage, solar input, IR loss to space, etc., and put it all into one package. They may have expressed all this in a series of equations and put it into a computer, and done some calculations to see what happens over time. Try searching for "general circulation model", along with "climate". If you are really, really lucky, someone will have brought together a group of scientists to review the work that has been done as described in the preceeding paragraph, and put it together in a summary of the state-of-the-art knowledge of our climate. You can start your search here. What you will find is that when science's best understanding of the complex systems involved is used, the current warming rates cannot be explained by TSI and time lags. -
DSL at 07:39 AM on 10 October 2012Climate time lag
Falkenherz - "My reasoning is that TSI is the primary cause for all other effects, which build upon and react to it. TSI changes will affect all other forcings, but no other forcing will affect TSI, but is dependend on TSI instead." That's precisely why I brought up energy exchange at the ocean surface. GHG forcing can directly affect how much solar energy is stored in the oceans (and thus made subject to oceanic circulation). If you want to understand AGW, you can't start with the surface temp record. You have to start with the physical mechanism--absorption/emission of thermal infrared radiation. Once you understand that that physical mechanism exists with a very high degree of certainty, it must then be accounted for. Solar's going to do what solar does. GHG forcing is going to do what it does. The relative strengths of both have not been determined by the surface temp record. Downwelling radiative flux has been directly, instrumentally measured at both surface and TOA. That energy must be accounted for. Must be. In every calculation. In every curve fitting exercise. It can't be disappeared by an alternative theory, unless that theory includes a way for multiple instruments to be precisely wrong hundreds of times and for applications that rely on known physics to suddenly stop working. If you ultimately find that scientists have made a mistake, that solar actually is responsible for the current trend, then we're in deep doo doo, because that energy stored via GHGs is building up somewhere. -
funglestrumpet at 07:15 AM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
I really would like to think that this video is real, but it conflicts with what Lord Monckton says, and he is a Viscount, no less, so he should know. -
wili at 07:00 AM on 10 October 2012Modelling the permafrost carbon feedback
Thanks to all who posted here and to Andy S for bringing this to our attention. I don't want to get off topic on the "panic" thing, but the image you have to have of the American public and of our decision makers is one of what is known as a "couch potato"--someone who spends all day on the couch drinking beer and watching TV. The only think likely to wedge such a creature from its perch is the perception/understanding that his house is on fire. Anything short of that will just be passed off as something he can get to later. Once panic gets him up and moving, that will be the time for him to come to some coherent plan. But voices telling him "the smoke coming from the next room probably isn't going to threaten you any time soon" are not going to motivate any action. Again, the reality of how policy responds (according to Schlessinger who spent his life working in these areas at top levels) is that the only actual alternative to at least a bit of motivational panic is complacency, which is pretty much what we've had. If proof (or at least strong evidence) that we have passed into a runaway greenhouse world--which I take this article to be, and I have not so far seen anyone argue convincingly otherwise--isn't cause for some strongly motivational panic to get us and our leaders off of our collective couches, I don't know what will be, besides utter collapse, at which point it will really really be too late. Best, and thank again to all. wili -
Daniel Bailey at 06:44 AM on 10 October 2012Climate time lag
@ Falkenherz: Lacking the understanding of the physics and the physical mechanisms themselves, you could choose: 1. To study those things, including the differences between the various feedbacks and forcings 2. To ignore number 1 above and continue to practice climastrology and curve-fitting; the modern equivalent of eye of newt and toe of frog Your comment above makes it clear you choose option number 2, so I'm bowing out of this discussion. -
Rob Painting at 05:23 AM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
The Franz Josef glacier has undergone spectacular retreat in the last few years. See the images here. -
william5331 at 04:28 AM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
The only reason the Fox and the Frans Yosef glaciers in New Zealand are advancing is because of the unbelievable amounts of precipitation falling in the snow fields where they start and these short periods of advance are in the middle of a long term retreat. The mountains are very very steep on the west coast of South Island where they occur and the glaciers poke right down into a temperate rain forest. If you walk up from the bottom of the valley you see a wonderful sequence of land reclamation by nature with forests at the bottom and only lichens and mosses right up beside the toe of the glacier. All this has happened within the past couple of hundred years. In no meaningful way can we say that these glaciers are advancing. -
Climate time lag
Falkenherz - "My reasoning is that TSI is the primary cause for all other effects, which build upon and react to it. TSI changes will affect all other forcings, but no other forcing will affect TSI, but is dependend on TSI instead." Actually, that is entirely incorrect. Anthropogenic greenhouse gases and volcanic aerosols are not dependent upon TSI - they are separate influences. Neither is (at least, not directly) the quasi-periodic ENSO variation. None of these are dependent on TSI, none are driven by TSI temporal patterns. If you treat TSI as the only driver, the "first cause", you will be starting from an erroneous premise - and will therefore come to erroneous conclusions. TSI certainly needs attention - but that is no reason to ignore GHG forcings, which on a purely physics basis are much more relevant to recent climate change. You seem quite strongly motivated to find a TSI explanation for recent climate change - I would suggest instead looking at the evidence and seeing where that leads. Motivated reasoning leads to confirmation bias, which (IMO) is what you are exhibiting - asking for stronger and stronger evidence for points you disagree with, while having an extremely low bar regarding evidence supporting your position(s) (proposing multiple century TSI lag is but one example). The evidence, from multiple lines of investigation and 150 years of physics, shows that our emissions are strongly affecting the climate, that they are the dominant influence right now. That is really the only answer a true skeptic should need. -
Falkenherz at 03:34 AM on 10 October 2012Climate time lag
KR, thanks, your comment corresponds to my interim-conclusion. However, I have to explore the sceptical further, because I still do not know sufficiently how strong TSI affects that sum of all forcings. My reasoning is that TSI is the primary cause for all other effects, which build upon and react to it. TSI changes will affect all other forcings, but no other forcing will affect TSI, but is dependend on TSI instead. That is why I believe TSI needs at least as much scrutinity as GHG, albedo and everything else. Spaerica, thank you very much for the link to reconstruction models. Scepticalscience indeed seems to offer a whole virtual library. Just a short comment on your three points: First, the displacement is only an estimate, so what, we don't seem to have anything better. Second, the "climate" lag should be the same for all kinds of radiative forcings. We know about lag, so we can as well try visualize it. Third, the system is indeed very complex but TSI is, by logic, not the least but the main factor, see my comment above. The impact, based on the known observations, might as well be small, though. Eric, I must admit you talk too scientifically abstract for me to understand. But I have the impression that your thoughts follows along similar lines which I tried to discuss here so far. But see also to Spaericas objections. Imo, key is, how much difference of TSI level can we establish and how is global temperature affected on the long term, including the "lag argument" which this article here is about. I will take some time to study the article about Saphiro et al.; on first glance, it seems the data I asked for is represented there, thanks again for that. -
Climate time lag
Falkenherz - Something important that I don't think is being emphasized enough in this discussion: the climate isn't responding to just TSI, to just, but rather to the sum of all forcings. And any lag in the transient or equilibrium climate response is to that sum of forcings. While there are some fingerprint particulars (faster response to TSI in the upper troposphere, for example), the overall efficacy of various forcings is close to identical, and what you need to look at is the sum forcing to see where the climate is going to go next. That total forcing is rising, and has been rising roughly linearly for half a century. The TSI component of that forcing has been declining over that period (and rather redundantly is therefore not responsible for the rise in total forcings), but at nowhere near the rate that GHG forcings have increased. In causal terms, GHG increases are responsible for warming, while TSI decreases are in turn responsible for limiting that warming somewhat. Given the (supported by the physics) climate lag response of 25-50 years, what happened in 1700 simply isn't relevant to this past century. It's not the sun. "Eyecrometer" time displacements simply won't make it so... -
Lambda 3.0 at 02:23 AM on 10 October 2012Update from Easton Glacier: Climate Crocks on Ice
When I tell people about the glacier melting or the arctic melting, I sometimes get asked, "why does it matter?" These glaciers make up a large part of the water supply for major cities and agriculture in many parts of the world. Without them, a lot of Great Plains agriculture would be impossible. A lot of western cities would be impossible as well. Not to mention a lot of the south Asian population would be put under severe distress. We're talking about potential upheavals of millions of people having no water to drink and less food to eat. Yes, it is a serious problem. -
DSL at 01:44 AM on 10 October 2012Climate time lag
On small improvement to the water tank analogy: instead of plugging up holes, we're placing screens over the holes, and as GHG concentration rises, the screen mesh gets tighter. There's something else, though, that I recall having been brought up at SoD. Does down-welling longwave radiation decrease the cooling efficiency of the mixed ocean layer (1-2m). In other words, as the skin receives more thermal IR, does it in turn prevent the mixed layer from getting rid of its energy -- to some degree, of course? This is an area where I'm still in the dark. The SoD discussions seem to be inconclusive on the incorporation of DLR into the general ocean heating mechanism. SkS doesn't have a post on it that I'm aware of.Moderator Response:[DB] I think you'll find your answer here:
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Bob Lacatena at 00:01 AM on 10 October 2012Climate time lag
360, Falkenherz, There are many solar reconstructions (through proxies), and many of them are at odds with each other. Be careful to avoid confirmation bias by choosing the reconstruction which best fits your hypothesis. You can find a discussion of two such reconstructions here. Separate from this... displacing a TSI graph would not be the right thing to do for three reasons. First, the displacement is only an estimate, and one with a broad range (25 to 50 years, a 25 year range). Second, and more importantly, to do so would imply that the sun's rays that struck the planet X years ago have a direct effect X years later. This is simply not the case. The imbalance at any point in time changes dramatically from day to day, month to month and year to year. It is impacted by multiple factors beyond TSI (albedo and GHGs being the two biggest). The change in global mean temperature at any one point in time is a function of the imbalance at that moment. The cumulative change over time is a function of the progressive imbalances, not a sum of the factors that caused the imbalances. Third, the system is just far too complex, and TSI is the least of the factors to be considered. Let's take Bob's water tank analogy and change it a bit. We have a tank of water with a hose (the sun) that is constantly filling it. The tank has holes so it is constantly emptying at, on average, the same rate as it is being filled. When the system is stable, the water level in the tank does not change. If we vary the flow of water into the tank over time so that on average it is the same as the amount exiting the tank through the holes, then on average the water level in the tank stays the same, although for short periods it will raise or lower. This will not be directly proportional to the changes in flow from the hose because, as has been explained, the increased pressure of a higher water level also causes the tank to drain more quickly. We can further complicate things by continually plugging some holes while other, new holes pop up, so that the amount of water leaving the tank changes. These are greenhouse gases. We'll also deflect some of the water coming from the hose so it splashes on the side of the tank instead of going in. These are anthropogenic dimming aerosols and volcanic eruptions. Now, out of all this, you want to take a graph of the water pressure in the hose for the past 12 hours, shift it 3 hours, and find some correlation with the height of the water in the tank... in a scenario where you know that the variation in the water pressure (flow) from the hose was in fact the smallest variable (i.e that the holes in the tank and the deflection of water away from the pool were larger factors in water level). Beyond this, you didn't even have a direct gauge on the hose until the last few hours, so you're guessing at the water pressure before then based on how loud the workmen thought it was, and you're not quite sure if you should be shifting it 2, 3 or 4 hours, and in fact you probably need to shift and distort the match-up by different amounts over time. You simply cannot naively take a graph of TSI, shift it X years, and say "ah-ha, now these should match up." It just doesn't work that way. The bottom line here that you do not seem to grasp is that things like this need to come from first principles. You need a coherent, logical reason as to why things would behave a certain way, make a quantifiable, mathematical prediction of what you expect to see, and then compare it to the result. You cannot take a thought process as simple as "hmmm, more or less sun should mean hotter or colder, and there must be a delay because it doesn't quite line up, so let's just shift these graphs left and right until we find a match." [h/t to Eric for pointing out not only that geometry reduces the W/m2 of TSI, but that albedo further reduces it. Also note that your 1880 choice is a cherry pick of a low, and one that egregiously ignores the "time lag" argument because it ignores the lag of the stronger TSI that preceded the low. The reality is that I still think you could claim at most 1 W/m2, divided by 4, times 0.7 for albedo giving 0.175 W/m2 or about .04˚C.] -
Eric (skeptic) at 22:58 PM on 9 October 2012Climate time lag
Falkenherz, it seems to me rather than a lag, the GAT response to a step TSI increase is an inverse exponential decay such as delta T = initial rise + rest of rise * (1 - exp( rate * time)). Of course TSI doesn't move in step functions. It's also been noted here that there is a modest 11 year signal in temperatures with no lag. My view is that there is a slight initial rise that produces the 11 year signal, but the rate of the exponential rise is slow due to ocean overturning. I'm not sure what you are talking about regarding 1880 and 1960, they differ by about 1.7W/m2 show here: http://colli239.fts.educ.msu.edu/2003/12/31/solar-activity-2003/ which translates to 0.3W/m2 after accounting for the spherical earth and 0.3 albedo. Using 0.75K/W/m2 sensitivity, that's about 0.2C. Dikran, I'm not sure if this is a radiation physics issue or an ocean response issue (not that simple either). That's because my presupposition is that secular CO2 forcing and secular TSI forcing lead to similar climate responses. -
Lionel A at 22:01 PM on 9 October 2012Update from Easton Glacier: Climate Crocks on Ice
I hope you don't mind me dropping in a post I made at Deltoid about a week ago, with slight edits. Of course when the 'usual suspects' of the world try to rubbish the scientific data they should consider going out on the ice like Dr. Mauri Pelto on Easton Glacier nr. Mt Baker in the Cascades – (video in a recent Climate Crocks post) and take Watts, Montford, Monckton, Bast, Bastardi, old uncle Tom Cobbly an’ all (that latter BTW idiom for the short list of high profile one-time scientists turned advocacy shills) with them. Think of the fun they would have howling at the moon that global warming is a hoax. Inhofe & co. could be dropped in by parachute – after all they could find a ready made igloo – in a crevasse. Those described above should pay attention to this bit, transcript as close as I could make out:This is just one measurement. Obviously the last two day we’ve marched around these glaciers, arggh, we’re going to cover about ten miles to get those two hundred measurements. Do that for thirty years on ten different glaciers and you get an idea of what it takes you to – just one little – you look at those graphs and you see a data series, a time series, even for an individual glacier or a series of glaciers in one range it gives you an idea of the kinda effort you need to put in.
That is what it is about, collecting the data for analysis to provide the information that informs us that global warming is for real. Anybody now continuing to obfuscate this basic fact should be sent for correction training to find out how science really works. Hey Watts & co., guess what, it isn’t sitting in a nice office somewhere comfortable confabulating over weather station photographs. You are behaving in a despicable deceiving manner by trying to deflect from the physical and mental effort of real scientists working in hostile and dangerous places. And yes I remember an acquittance of mine who disappeared, never to be seen again, into a crevasse on Greenland. -
Falkenherz at 21:02 PM on 9 October 2012Climate time lag
Dear co-commenters.... I think I found a big part of the answer, from Wang 2005 (which I had already read and quoted, but under a different article, so I forgot it; that's what I get from jumping from article to article with the same question...). Wang 2005 presents a model (ok, a model, but better than nothing), which goes back until 1700. It shows *only a small difference* in TSI levels in 1700, as compared to 1880 and 1960 (Fig. 15 on p. 535). Consequently, a trailing off of the global temperature (=response) from 1960 onwards can only correspond to a fraction of the difference between TSI levels in 1700 and 1960. Now I only need to see some corresponding observations, reconstructions, models of global temperature levels from 1700 onwards. This would help me to understand the possible scale of the long-term response linked to a dominant TSI forcing. Can someone point me to a source? Interim-conclusion: Even if we assume that a halting TSI level in 1960 still incurs some lagged/trailing-off raise of global temperature, the scale of this temperature lag could be too low to have any significant part of the response we saw since 1960, and it should have ended around 2012 (50 years since 1960). However, I am still puzzled that global temperature and TSI curve are directly compared instead of deplacing it on the timeline (x-axis), according to the lag time we know (25-50 years, say, 40 years). -
Dikran Marsupial at 20:59 PM on 9 October 2012Climate time lag
Falkenherz, you will find that contributors here are not likely to be impressed with you using the points they raise simply to try an create a contradiction where none actually exists ("But then, suddenly, Dikran #352...". Instead you would encourage better discussion if you were to actually engage with the points raised. Do you agree with the physics of my post, or not. If not, please explain why. At the end of the day, you need to understand the physics pretty well to know what you can logically conclude from the data. You would be better of learning the physics and attempting the data analysis later, when you have a better grounding (which is why I don't often comment on radiative physics issues). -
ajki at 19:27 PM on 9 October 20122012 SkS Weekly Digest #40
Side note unrelated to the topics of this digest: Early in 2012 german readers saw the phenomenal rise of a new bestseller on the german book market, still provided in piles in all book stores. Even my local public library has bought two books - so for the next five to ten years Vahrenholt/Lüning's 'Die kalte Sonne' will be available here for all citizens. Vahrenholt and his 'insights' on climate change have been noticed and to some extent covered on SkS here [dana1981] and here [Bart Verheggen]. But until now english speaking readers did not have the questionable pleasure to read about Vahrenholt's positions directly. But generously Prof Vahrenholt made available a lecture held on 06/13/2012 at the Royal Society in London with the title “Global Warming: Second Thoughts Of An Environmentalist” on his website [www.kaltesonne.de]. A pdf in english is downloadable from this page [direct link to pdf]. -
Falkenherz at 19:18 PM on 9 October 2012Climate time lag
Quoting from this article here: "How long does the climate take to return to equilibrium? The lag is a function of climate sensitivity. The more sensitive climate is, the longer the lag. Hansen 2005 estimates the climate lag time is between 25 to 50 years. How would climate have responded to the solar levels maxing out in the 50's? For the next few decades after the 50's, the radiative imbalance would've gradually decreased until the climate reached radiative equilibrium around the late 80's (give or take a decade)." Consequently from Bob #318: "If you see someone talking about time lags that mysteriously come and go (or change in duration) depending on whether they are "needed"or not, then chances are that the "time lag" doesn't have any physics behind it - just rhetoric." But then, suddenly, Dikran #352 "...Thus it seems to me that the response to TSI should be much more rapid than the adjustment to CO2..." ... and, gws #357 "The warming mechanism between increased atmospheric CO2 and increased TSI is not the same, hence you cannot infer that you would have to get the same lag times." And thanks for the honey, but the only thing I am doing is asking logical questions, and I expect logical/coherent answers. I do this here, I do this on sceptic pages. As you can see from the quotes, there seems to be a mismatch. This article should then explicitly explain, why TSI has much shorter "climate" lag (i.e. responses by global temperature) than a given alteration of the CO2-level. Bob, I totally recognize the point that we don't see a gradual decrease, a trailing off, YET!!! I simply question the time scale on which we should expect to see a decrease. So, again, my hypthesis is that 0,6 Degree are not caused by GHG/CO2 alone, that some part is still due to a TSI lag. You admit this yourself by reverting to the common statement that CO2 took over as a "dominant driver". By logic, for CO2 to take over from 1960, this means that CO2 (in the air in 1920 with a lagged response of 40 years, in 1960) should have more effect than TSI in 1920 (from 1920 with a lagged response of 40 years, in 1960). Again: Because this is the climate lag which this article states does exist! And this article explicitly takes the "solar energy" as an example for that lag! Also: As you all state repeatedly, TSI is just one factor, and GHG/CO2 adds on top; by logic, this should delay any visible lagged response to a stabilizing TSI from 1960. We can now argue that the TSI contribution from before 1960 to global warming since 1960 should be neclectably low, but again, this can only be stated coherently if you take a perspective since 1880. Because, there is only a very low upward-adjustment of the TSI level in 1960, compared to 1880. As I asked repeatedly, I would like this theory to be confirmed also on the basis of a long-term observation, since 1700. If we *should* observe a high upward-adjustment of the TSI level in 1960, compared to 1700, the process of trailing off *could* happen on a much larger scale, right? Why is this question so difficult to accept? -
EliRabett at 12:51 PM on 9 October 20122012 SkS Weekly News Round-Up #4
Not quite sure why anyone should be surprised by the aerosol aging paper -
Eric (skeptic) at 12:11 PM on 9 October 2012It's the sun
As Bob explained to me up thread there are various time constants for warming of lower layers of the ocean. There should thus be a roughly exponential rise in GAT (atmosphere) based on those time constants after the immediate GAT rise. The annual cycle of solar means it can only perturb the mixed layer before cycling back. A secular rise in solar would affect the deeper layers for which we would have to derive time constants. -
Riduna at 12:04 PM on 9 October 2012Sea Level Isn't Level: Ocean Siphoning, Levered Continents and the Holocene Sea Level Highstand
Rob - interesting. Can we assume that isostatic rebound and seafloor collapse occur at the same rate and if not, why? And what about the effects of gravity which the geoid shows are not evenly distributed? -
JasonB at 12:00 PM on 9 October 2012The Economic Damage of Climate Denial
I haven't gone through funglestrumpet's link in detail, but (apart from the general polemic tone of the writing) I did note that he makes a big deal about "energy density" as if this automatically is some sort of death blow to renewable energy. I've seen this kind of thinking elsewhere as well, ignoring the following facts: 1. While the area required for wind is large, that area doesn't need to be exclusively used for wind. In fact, every wind farm I've ever seen has been on land that was also being used for agriculture, and as far as I could tell (and from what I've read) the wind farm has little to no impact on the use of the land for its original purpose. 2. The area required for a coal-fired power station might be small, but it's ignoring the area required for mining that coal, which is incredibly large. See SourceWatch for one attempt to calculate some figures for the US. The bottom line is that the area that has been already disturbed by coal mining probably exceeds the total land area required to power the entire USA by solar thermal alone, and apparently nobody thought that was an obstacle to the use of coal. On top of that, coal tends to be found in forested and agricultural areas whereas the best sites for solar thermal tend to be deserts. I agree with KR that McKay's book is a good read. I also agree that it's important to put it into context -- the UK is unusually dense, small, and far from the equator. The idea that the UK should be able to take advantage of a switch to renewables to wean itself off energy imports seems fanciful -- it imports energy now, and it will need to continue doing so in future. Conclusions that apply to the UK hardly apply to the majority of the world. Another general tendency I've seen is for magic bullet thinking, and to rule out any technology that can't economically provide 100% of future needs. This is an unrealistic and unnecessary hurdle. After all, none of the current technologies are attractive if you scale them up to 100%. We use a mix of technologies right now precisely because of this. While we argue about whether wind or solar are viable at high levels of grid penetration, we miss out on the opportunity to bring them up to their optimal levels of grid penetration while giving us more time to solve those problems or find better alternatives. What are the optimal levels? Well, according to the NREL, at penetration rates of up to 6%, solar PV is actually beneficial because it allows less usage of peaking power generators. At higher rates, however, it’s generating so much power at peak times that it causes a problem because the existing baseload generators have difficulty scaling back output, and scaling them back to their minimum output, then adding in wind plus solar PV, actually results in generation greater than the load. However, replacing traditional plants with solar thermal plants with heat storage actually increases the penetration ability of PV because the solar thermal plants have higher ramp rates and lower minimum outputs than traditional large thermal plants. The solar thermal plants increase grid flexibility and its ability to accommodate wind and PV, to the extent that a total solar contribution in excess of 50% (PV + CSP) becomes viable. Adopting solar thermal, solar PV, and wind on a large scale while researching fusion and trying to make thorium reactors economically viable seems like a good strategy to me. Complaining about how wind farms and solar powerplants look while ignoring how coal mines look seems rather selective. Like KR, I'd much rather have the former nearby than the latter. -
AlanInAZ at 11:24 AM on 9 October 2012Nate Silver's Climate Chapter and What We Can Learn From It
I think this review is from a fan who would really not like to criticize someone he respects. I have read the chapter and the impression left with me is that climate scientists and acolytes like Gore tend to over state impacts. Silver leaves the impression that we can wait until predictions are more certain before pushing for difficult political decisions. Geo-engineering will come to the rescue if needed. He has the nerve to cite big Pharma and their patents as an example of our potential for technical innovation. The section on Nordhaus was only two sentences and lost in the considerable noise of the chapter. The book is good except for the climate chapter and that contrast increases my disappointment. -
Bernard J. at 09:05 AM on 9 October 2012It's the sun
The atmosphere, in particular the upper troposphere (RSS/UAH) responds quite quickly to changes in TSI. Overall effects (larger temperature swings) will occur over longer periods due to the thermal buffering of the oceans, but there is a fairly immediate and detectable atmosphere response.
Indeed - as the seasonal changes in response to annual hemispherical insolation changes suggest.
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