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Climate time lag

Posted on 8 July 2009 by John Cook

The previous post on CO2/Temperature correlation sparked some interesting comments on climate time lag. Unfortunately, the discussion went pear shaped with some ideological anti-intellectualism and things got a little bitchy after that. Nevertheless, climate time lag is an important subject that deserves more attention. Several metaphors were invoked in an effort to explain the phenomenon including stove hot plates and warming baths. However, I find the best way to understand climate time lag is a direct look at the science.

Our climate receives its energy from the sun. The amount of energy the planet absorbs from the sun is calculated from this equation:

Incoming Energy Flux= πR2S(1-A)

R is the radius of the earth, S (the solar constant) is the energy flux from the sun and A is the Earth's albedo - around 30% of sunlight is reflected back to space. The earth also radiates energy into space. The amount of energy emitted is a function of its temperature:

Outgoing Energy Flux = 4πR2εσT4

σ is Boltzmann's constant, T is the absolute temperature in degrees Kelvin and ε is the average emissivity of the earth. Emissivity is a measure of how efficiently the earth radiates energy, between 0 and 1. A blackbody has an emissivity of 1. Greenhouse gases lower the earth's emissivity. When the climate is in equilibrium, energy in equals the energy out.

S(1-A) = 4εσT4

What happens if the sun warms (solar constant S increases) then maintains a sustained peak? This is what occured in the early 20th century when solar levels rose then plateaued at a hotter state in the 1950's. The radiative forcing from the warming sun is not particularly large - between 0.17 W/m2 (Wang 2005) to 0.23 W/m2 (Krivova 2007) since the Maunder Minimum. Nevertheless, let's assume for the sake of argument that there is some amplifying effect (perhaps the cosmic ray effect on clouds) so that the warming sun has a substantial effect on global temperature.

When the sun warms, initially more solar energy is coming in than is radiating back out. The earth accumulates heat and it's temperature rises. As the earth warms, the amount of energy radiating back out to space increases. Eventually, the energy out matches the incoming solar energy and the planet is in equilibrium again. The time lag is how long it takes climate to return to equilibrium.

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). So how has our planet's radiative imbalance evolved over the latter 20th century?


Figure 1: net radiation flux at the top of the atmosphere (Hansen 2005).

Hansen 2005 finds that the net radiative imbalance has steadily increased over the 20th century. There is no indication that the climate is heading towards equilibrium - quite the contrary. This is confirmed by satellite measurements of energy flux at the top of the atmosphere:


Figure 2: Global ocean heat storage (blue) against global net flux anomalies (Wong 2005).

The climate is not heading towards equilibrium. Rather, the radiative imbalance is increasing with the climate steadily receiving more energy than it is radiating back out into space. And this is where the true significance of climate time lag lies. Even if the radiative imbalance were to level off at its current rate of around 0.85W/m2, it would take several decades for the climate to return to radiative equilibrium. Based on this climate lag, Hansen 2005 calculates there is still 0.6°C warming still "in the pipeline".

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Comments 351 to 388 out of 388:

  1. gws, if global temp follows [cause], but takes time to reach and stabilize at a higher energy level (corresponds to global temperature) as given by [cause], than this applies to both CO2 and TSI. In that case, on that graph above you should move the blue curve (=cause) to the right, or the red curve (=effect) to the left, in order to correlate that lag properly. This whole article here talks about a climate lag of roughly 25-50 years, because of the time for the system to get back into energy equilibrum (which corresponds to a certain level of global temperature). Even the link from Daniel tells of a lag of 40 years for CO2 and states explicitly "With 40 years between cause and effect, it means that average temperatures of the last decade are a result of what we were thoughtlessly putting into the air in the 1960’s." Now delete from "what we were thoughtlessly" onwards and replace with "the TSI increase which started somewhere around 1700 and lasted until the 1960s". BUT, by contrary, when TSI is concerned everybody just seems to state that, since TSI stopped increasing in 1960, then instantly, without any lag, any further rise of global temperature after 1960, the 0,6 Degrees since then, MUST be attributed to CO2. Apparently I am the only one who finds that odd. The only reason I can see as a logical argument is, if TSI rose only by minimal amount since *1700* (why do everybody here seem to assume they can ignore anything that happened with TSI and global temp before 1880?), because in that case, indeed there would be no physical possibility for a lagged increase of an amount of ~0,6 Degree. DSL, Forster and Rahmsdorff 2011 calculate the rate of rise of temperature ("the warming rate is steady over the whole time interval"). This. is. not. my. point. Side remark, the quoted essay of Krinova in the article speaks of going back to the maunder minimum, but the models they create go only back to 1868. That's not the maunder minimum. I can just assess the abstract, though.
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  2. Falkenherz, radiative physics isn't my strong suit, so hopefully my better informed colleagues can correct me if I am mistaken, but in this context I would have thought there is a difference between CO2 and TSI forcing. For CO2 forcing, increased CO2 raises the altitude in the atmosphere from which IR photons can escape into space. Due to the lapse rate, this higher layer will be colder, and hence the amount of IR radiated into space will be lower. As a result, the Earth will gain energy until the atmosphere warms sufficiently for the emitting layer to warm enough to radiate away as much energy as is coming in. For the atmosphere to warm, the oceans need to warm as well, and that causes a lag. TSI is rather different, imagine the height of the emitting layer remains constant. If TSI rises slightly, so that more energy comes in than is radiated away into space, there will be an energy imbalance, and the Earth will begin to warm. However if TSI then drops back to its equilibrium level, the energy imbalance disappears and the warming relatively quickly stops. Thus it seems to me that the response to TSI should be much more rapid than the adjustment to CO2, unless there is suddenly a way to scrub vast quantities of CO2 from the atmosphere and bring the height of the emitting layer back down again.
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  3. Falkenherz - CO2 did not magically appear as a forcing in the 1960's. Rather, it was around the 1960's when insolation took a downward turn, and when CO2 became the dominant forcing. And continued to rise in forcing strength as it has since the start of the industrial revolution. If you look at net forcings (as I showed here), they have been increasing roughly linearly for the last 40-50 years. Temperatures have also been rising roughly linearly over that time frame - not showing an exponential rate decay towards equilibrium, but rather following the forcings upwards. TSI has decreased over that interval, CO2 forcing has continued to increase. That temporal relationship clearly shows that recent warming (over the last half-century) is not due to the sun - and in fact, decreasing insolation has noticeably slowed the warming. If you wish to chase this TSI windmill any further, I would strongly suggest taking to the far more appropriate Solar activity & climate thread.
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  4. Falkenherz, to make that substitution is inapplicable and demonstrates a lack of understanding on your part between forcings, feedbacks and the physical interconnections of our world. I suggest listening and reading more. I am not the only one doubting the existence of these "other skeptics" you paraphrase.
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  5. Dikran, Falkenherz - I have responded on the appropriate thread here.
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  6. Falkenherz: I'm a bit busy, so I can only give you a few minutes at the moment. I may be able to follow over to the radiative transfer stuff a bit later, but for now I'm still on the "time lag" issue. Let's look at an analogy. You have a tall tank full of water. You put a small hole near the bottom. Water starts to drain out the hole. The final equilibrium water level is down where the hole is, but that won't happen instantaneously - it takes time. Let's assume the tank is large enough, and the hole is small enough that this will take 40 years. Thus, the time lag to equilibrium is 40 years. ...but water starts to leak out right at the beginning. What is the rate of leakage over time? Well, the leak rate depends on the pressure forcing water out the hole (plus the size of the hole), which is related to the height of the water above the hole (technically, the height difference). At the start, there will be a relatively rapid loss of water and a rapid decrease in the level in the tank, because the pressure is high (the full height of the tank). As water drains out, the height of the water decreases, the pressure decreases, and the flow rate decreases. Near the end, as we approach equilibrium, we only see a trickle of water, and the level in the tank is dropping very slowly. Note that we are committed to draining the tank as soon as we make the hole (unless we find a way to plug it). So someone coming in half way is going to be looking at a leak that is the result of an imbalance (hole) made 20 years ago, and the time lag in fully draining the tank means the leak will continue for another 20 years (time lag). The rest of the leakage is "in the pipeline" already (to make a bad pun, but using a term that is often used in climate change discussions). That person arriving at the 20 year point will be seeing a leak that was faster in the past, and gets slower in the future. What we don't expect to see is a pattern where nothing happens for 20 years after the hole is made, then the leak gradually gets faster and faster as the tank begins to drain. The physics just doesn't work that way. If you arrive at the tank after 20 years, and see the water level dropping at an increasingly faster rate, then you need to look for new leaks, not blame it on the hole that was made 20 years ago. To tie the analogy back to climate and radiation forcing, the pressure in the water tank is the radiative imbalance (sun pushing energy in minus the current IR loss to space). The flow out the hole is the increased loss of IR to space needed to eventually restore equilibrium. The level in the tank is temperature. For climate, the radiative imbalance is largest at the start and gets smaller over time, the temperature rises fastest at the start and slows over time, and the equilibrium temperature change is committed as soon as the radiative imbalance is created. It's kind of a backward analogy, because the water tank is losing water, while the earth is gaining energy (increased TSI, or CO2 reducing IR losses, leading to a net positive radiation balance), but hopefully you can easily visualize the water tank and how it responds, to understand how time and changing fluxes/levels factor in to restore equilibrium. Like all analogies, this one is full of holes (in addition to the one the water is leaking from), so first just try to make sure you understand the physics of the leaking tank, before trying to apply it to the global radiation balance. ...and the TSI increase vs. CO2 increase effects are, to a first approximation, not much different.
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  7. Falkenherz @351 Your response shows you are a keen observer and have read through numerous papers, unlike your previous modesty about your knowledge. Your continued playing of devil's advocate starts to look strange to me. I asked about your understanding of the lag mechanism both verbally (again above by Bob) and graphically explained to you. It would help if we knew your answer. To repeat Daniel: 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.
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  8. 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?
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  9. 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).
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  10. 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).
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  11. 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.
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  12. 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.]
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  13. 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.
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    Moderator Response:

    [DB] I think you'll find your answer here:

    How Increasing Carbon Dioxide Heats The Ocean

  14. 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...
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  15. 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.
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  16. 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.
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  17. @ 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.
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  18. 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.
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  19. 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.
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  20. 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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  21. 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.
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    Moderator Response: [DB] Tone-trolling snipped.
  22. 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.
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  23. 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.
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  24. 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: Image and video hosting by TinyPic 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: Image and video hosting by TinyPic 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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  25. 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: Image and video hosting by TinyPic 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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  26. A single lag time is insufficient to describe the observed climate response (as in Bob Loblaw's post, the model shouldn't be too simple). Tamino has an excellent post on this, Fake Forcing, where he examines attempts to use single lags - attempts that require ad hoc, physically unsupported tweaks to come even close; the "fake forcings". On the other hand, if you consider a two-box model, two time lags, roughly corresponding to the responses of atmosphere and oceans, you can replicate climate behavior quite well. That model (lags in Taminos example of 2 and 45 years, respectively) fits observations quite well without modifications, and has the added benefit of being based on physics. It also directly provides an estimate of climate sensitivity using purely instrumental data, of 2.4C/doubling of CO2, well within IPCC estimates. Sliding time-lines back and forth for visual matching (which also neglects the fact that the climate responds to all forcings, not just one, and that analysis should be measured by statistics, not the "eyecrometer") is equivalent to using a single-box model - that's just too simple to describe observed climate behavior.
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  27. KR, indeed. That is why I commented that this is Falkenherz's "thought experiment". As the long time lag dominates, the picture is not too far off, but as was commented here before, the shorter air-T time lag has additional effects that make it more realistic.
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  28. Seems to me that the OP would benefit from an update that incorporates the some of the detailed comments being made in response to Falkenherz.
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  29. John, I would welcome that. In my opinion, some clarification would be good. Talking about global temperature being submitted to a "climate" lag is one thing, and my discussion was focusing on that. But the article jumps midway into talking about an inceased radiative imbalance. I believe these are two totally different things, and this could be clarified. Bob, my approach is rather to go from simple to more complicated. It's the natural learning process this way. gws, a lot of work, and believe me when I say I do not understand Math formulas (as I have for example no clue what a multiplier to a multiplier in brackets minus something should tell me in the end). The conclusion is of course nothing new. I was aware that most of part of the response was already before 1960; that's why we were talking about a trailing-off, and I was trying to focus on what level of difference we are actually looking at in order to determine the scale of trailing-off we should take into account. BTW, in the Saphiro article, which Sphaerica linked to, I can do a lot of observations which show that directly comparing TSI to GT on a under-100-year scale makes absolutely no sense. Sometimes you see an almost direct response, sometimes none at all. I am trying to comment that over there. My bottomline for the climate lag article here; it should probably explain how "radiative imbalance" is calculated without resorting to global temperature, as the latter seems to greatly mislead.
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  30. Falkenherz, The article does not "jump." It introduces a key concept, radiative imbalance, and then relates it to the problem. It is, in fact, the crux of the above post. I agree that it could be clarified, but you can't expect every blog post to qualify and explain every single detail within it. At some point you have to say "gee, radiative imbalance, I don't quite understand that, maybe I should go read up on it and then come back and re-read this article again." Or, you could invite a lengthy stream of comments, all of which explain it to you, and yet...
    I believe these are two totally different things...
    1) Don't say "I believe." There is no "believe" in science. There is "I understand" and "I don't understand." If you say the latter, then you have more to learn. Period. Your statement is also an insult to all of the people who have posted responses to you and tried to explain it to you. Basically what you are saying is that you still don't understand and don't want to be bothered, you'd rather stick with your initial and wrong misconception. And they both are and are not two totally different things. They are different in that one (radiative imbalance) is the cause of the other (temperature change with a lag). But you can't separate them. Climate lag is not a magical fairy effect imposed by the cosmic climate-lag equation of ∂T = ΕWr⁰Ng. It is a manifestation of the fact that radiative imbalances are small compared to the heat capacity of the earth, and so that imbalance must be maintained and constant over a long period of time for a forcing to have a noticeable effect on global mean temperature. If the forcing is not large enough or not constant, there is no detectable change. If there is a detectable change, it is not linear. You need to go study radiative imbalance and understand this before you can continue. You cannot choose to skip this simply because you want to "keep it simple." That's like saying traffic signs and stop lights are too complicated. You're a new driver. It's hard enough to steer and press the gas and brake pedals, so you want to be allowed to drive around for a few weeks without paying attention to those bothersome traffic signs and laws. They just get in your way.
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  31. Sphaerica... "Your statement is also an insult to all of the people who have posted responses ..." Look, it is rather easy to blame me. All I did in the beginning here, at #295, was ask a simple question, which could have answered with a simple "no" and some explanations, and those could be included into the article. Instead, most of the comments I received back were like "what nonsense are you talking about?", pressing me to justify my questioning and my intellect. I was at no point getting personal to anybody, but I do not feel treated in kind. ( -snip-) Let's leave it at that, this is getting out of hand and not helping anybody to understand things better. Thanks for all the answers I actually was able to pick out of the sum of all comments, they nevertheless helped me understand some things.
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    Moderator Response: [DB] Moderation complaints snipped.
  32. Falkenherz, It is, unfortunately, common that people do not talk "eye-to-eye", and online, without benefit of direct feedback or physiognomy, even more so. That said, people here immediately responded asking you to be clearer on message. It took a while before it was understood here that you meant to say that "serious" skeptics argue that "TSI drives all other changes" (your initial "top-up"), aka also the observed CO2 increases. Needless to repeat ?: No, no evidence for that being the current mechanism of climate change. Instead, plenty of evidence for the universally acceptance mechanism. And no, no hard feelings, you are welcome to be back with more as long as it's not too far our ;-)
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  33. Sorry, Falkenherz, I lost track of you. Everyone did answer your question, repeatedly, and you ignored the answers and just kept grasping at straws, hence my attitude. You can't be bothered to understand the science, but then are annoyed that people can't explain it to you on a kindergarten level. Yet you were clearly never interested in getting answers, but simply pretending to care so you could argue a case that you believe in (even though you claim not to). Today you are posting about this thread on WUWT as "thingadonta" and exposing your true nature there.
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  34. Another sock puppet, another fake skeptic. I thought that Falkenherz' style was somewhat familiar. And these clowns wonder why they run into less than polite attitudes. I bet he didn't get any grief from Watts for posting under an anonymous handle...
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  35. Philippe, thanks for the compliments, and I am still here, hopping though articles which come most close to my questions and trying to grasp things. I try to inicate where I leave off and move on to; maybe that was not clear enough. I left to discuss the article of Shapiro e.a., got another referral and moved to "how sensitive is our climate", and from there, by another referral, went to Shakun e.a.. There I tried to comment, but somehow my comments do not arrive there. BTW, Sphaerica, you must confuse me. I did not write as thingadota, I fact I believe I disagreed with him on the implications of the PETM somewhere on this website. But as you can see from your link to WUWT, I was right that some sceptics like to use the arguments I was inquiring about here.
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  36. (-snip-). (-snip-). Really, you could have left with gws#382 as a nice wrap up, but you had to have to launch some unfounded allegations towards me as some last words. That really does annoy me now and I ask you - with all due respect - to be a bit more careful before accusing people without reason.
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    Moderator Response: [DB] Please, can we all focus on the topic of this thread? Thank you. Off-topic snipped.
  37. OK, Falkenherz. You say you're not thingadonta, so in the post at WUWT that Sphaerica linked to, thingadonta says" "Daytime temperatures peak hours after noon, seasonal temperatures peak weeks after the solstice, it is a simple idea to translate this to longer term solar forcing, too simple for many alarmists to even comprehend." From your understanding of what has been discussed here, would you care to explain why thingadonta is is just plain wrong? Or would you agree with his statement?
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  38. Sorry Falkenherz, I don't really believe you. You may not be Thingadonta, that would be good for you, because years ago he was explained by me what the diurnal temperature variation is about, and now he still shows his lack of understanding. Bob's request, however, is very relevant, I would more than welcome an explanation from on the diurnal temperature variation as it related to incoming solar energy. Hint: it's really not complicated at all. You displayed a dismissive attitude and rather strange interpretation of the existing science on the relationship between Milankovitch cycles and glacial cycles. That was based on minimal and superficial knowledge, despite my pointing you to the works of Berger and Loutre, which would themselves cite the works of many others. So far, I have no choice but to interpret that your "grasping" is somewhat selective and likely heading in a predetermined direction.
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