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Doug Bostrom at 16:27 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Wes, you mention "catastrophic collapse" and then within a handful of words yourself concede that's not actually the issue. Thanks for the swift return to reality. ...even though the current melt rate in the graph above if it continues uninterrupted indicates a sea level rise of 1 metre around in around 800 years. Did you notice, the graph John displayed is curved, in the wrong direction? Surely, you don't doubt that peak oil-which is forecasted for virtually tomorrow- combined with exponentially accelerating technological evolution won't have pushed us well past a hydrocarbon-based economy long before then? A moving goal post we can agree on, and upon which I've got my hopes pinned. -
Steve L at 16:26 PM on 1 June 2010On the Question of Diminishing Arctic Ice Extent
"we expect the annual loss of sea ice to accelerate" -- maybe, but not based on the data. A statistical model like this isn't supposed to be projected into the future. A mechanistic model would allow you to do it. Moreover, it's quite possible that the decline in March maximum might start catching up to the decline in Sept minimum before the Sept minimum reaches zero. -
Doug Bostrom at 16:23 PM on 1 June 2010On the Question of Diminishing Arctic Ice Extent
Arctic sea ice: the Albino Canary in our global coal (and oil) mine. -
Sustainable2050 at 16:19 PM on 1 June 2010On the Question of Diminishing Arctic Ice Extent
Thanks for the overview. This all-season Arctic Sea Ice Volume graph (updated on a weekly basis) is also very compelling: Arctic Sea Ice Volume. Anomaly at an all-time low, and dropping at an increasing speed. -
wes george at 16:12 PM on 1 June 2010Latest GRACE data on Greenland ice mass
OK, so now we concede that concern for a catastrophic collapse of Greenland's ice sheet is based primarily upon the assumption that modern warming is anomalous and indeed, unprecedented in the Holocene? Fine. What we need are testable assumptions. Not strawmen. Speaking of strawmen, I understand that the real concern is the possibility that about 7% of the ice might melt by say 2090 leading to a one meter rise in sea levels, even though the current melt rate in the graph above if it continues uninterrupted indicates a sea level rise of 1 metre around in around 800 years. We've been through all that and it leads back to the whole unprecedented, anomalous warming meme. Because, if today's warming isn't anomalous and unprecedented then we could simply look at other warm periods in the recent holocene for guidance. Right? Moreover, even if today's relatively ordinary rate of warming (0.8c per century) is 100% anthropocentrically induced we won't be 1-2c warmer before 2080 to 2150. Surely, you don't doubt that peak oil-which is forecasted for virtually tomorrow- combined with exponentially accelerating technological evolution won't have pushed us well past a hydrocarbon-based economy long before then? -
Jeff Freymueller at 15:49 PM on 1 June 2010On the Question of Diminishing Arctic Ice Extent
"The two trendlines cross in 1980 (suggesting rather nonsensically that in years prior, the minimum ice extent was greater than the maximum)." Actually, no. Both of the curves are percent change from the 1970 values, so it just means that before 1980, the September data were, on average, a bit higher than Sep 1970, while the March data were a bit lower than March 1970. If you converted your two percentages back to actual extent, I'm sure you would find that Sep extent was always lower than Mar extent. The comparison of extent to winter SST anomaly is quite interesting, even though I am not sure how well the Pribilofs (southern Bering Sea) is a good proxy for the Arctic Ocean. I'm guessing it is the closest measurement you could find? Have you also tried air temperature at some of the Arctic weather stations? The obvious question is whether the extent vs. SST fits are more or less noisy than the extent vs. time plots. I can't tell because the scales are not the same. My eyeball says they are similar based on looking at the 1-sigma bounds, but it would be good to run the numbers. -
Doug Bostrom at 15:31 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Wes: Why would one cite evidence from 125,000 years ago, an entirely different era than the holocene? Indeed. Take a look at John's post, above. Notice the graph, showing an accelerating loss of ice, now. Nice, fresh data, no interpretation required. Why not look at more recent warming, say like in the last 4,000 years? How about going one better, and looking at the warming happening now? Warming, ice melting. What could be simpler? Wes, the ice sheet is melting right now, responding to a change in regime. What we know of the cause for that change suggests it's going to last for a long time. As John and others have mentioned, the issue is not that the ice sheet is going to vanish, not now and not in our great-grandchildren's time. That's not the salient issue so don't worry about it. Worry instead about how to arrest the decline we're seeing now. -
wes george at 15:18 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Why would one cite evidence from 125,000 years ago, an entirely different era than the holocene? Why not look at more recent warming, say like in the last 4,000 years? In the recent era surely many variables would be more tightly coupled to today than data from 125,000 years ago and have a higher resolution. Sure, there are no periods of recent past warming above today's temperature longer than a few centuries, perhaps even less. But our concern is melting over the next few decades rather than millennia. Why indeed look back 125,000? Because of the assumption that no recent past record of warming 1c to 2c higher than today exists. No? Certainly, Greenland didn’t melt much during recent warm periods. Ie, concern for a catastrophic collapse of Greenland's ice sheet is based primarily upon the assumption that modern warming is anomalous, indeed, unprecedented in the Holocene. So we got to go back 125,000 years to find a period where the sea-level was 6 plus meters higher than today? I find that an argument for the relative robustness of Greenland’s icecap rather than evidence that a 100,000 year old feature is likely to disappear rapidly due to a 1c to 2c temperature rise.Response: Why look back 125,000 years? You answered your own question - it's the most recent time when global temperatures were 1 to 2 degrees warmer than now.
Greenland didn't disappear 100,000 years ago - it's been around for at least half a million years. Using very rough back-of-the-napkin calculations, 6 metres sea level rise would receive perhaps 3 metres sea level rise from Greenland which would be less than half of the ice mass currently on the ice sheet. This is very roughly speaking, I'm not aware of the relative contributions from Antarctica versus Greenland.
The issue here isn't the total disintegration of Greenland (at least I hope it doesn't come to that). But even a partial collapse of the Greenland ice sheet will impose sea level rise in the order of metres plus a corresponding sea level rise from Antarctica (throw in melting glaciers and thermal expansion for good measure). -
scaddenp at 14:42 PM on 1 June 2010Latest GRACE data on Greenland ice mass
One other detail, you might like to look at the greenland past temperatures in Gareth's little graph for a perspective. The real issue is that unlike past natural variations, we expect warming to continue or even accelerate unless we reverse changes to atmospheric composition. It is what happens to this in future that will determine the fate of greenland ice sheet. -
scaddenp at 14:26 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Hmm. Younger dryas - I agree that the evidence points to the onset of COOLING as being very rapid. Also worth noting that younger dryas/Heinlich events would appear to be a feature of record only in times when moving out of glaciation. "Akkadian Collapse" - I know little about this but isnt this sudden onset of drought? What evidence that this was a global event rather than regional? I would take very little comfort from this or other records of regional disruption of the hydrological cycle. Rapid change from whatever reason is difficult to adapt to and the fact the AGW predicts more disruptions like this in various parts of the worlds is worrying. -
Doug Bostrom at 14:04 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Wes, I fail to see how the examples you're referring to address multiple lines of evidence indicating that Greenland's ice is shrinking at a rate that will combine with other contributors to exacerbate a developing problem w/sea level rise, now, when we're around to be affected by the result. How do you draw the conclusion that our concern for ice loss on Greenland is based on the fact that modern warming is anomalous? For most of us the issue is that the ice is in fact melting, which is not an assumption. -
wes george at 13:46 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Marcus # 25, contends that modern warming is occurring at an anomalously rapid rate. I understand there must be a bias toward gradualism in the climate sciences, but recent studies seem to indicate many instances of extremely violent climate change has occurred in the past. Best known of these being the onset and decline of the Younger Dryas and the so-called Akkadian Collapse both of which appear to have achieved their full amplitude in a matter of years rather than decades. I would also dispute Marcus's characterization of the onset of the MWP as gradualistic or any of the other recent warm or cooling periods. Most recent climate phase shifts occurred at rates exceeding .5c a decade. Again, the paleoclimate reconstructions favored by some in the community perhaps don't reflect the full extent of volatility of recent past climate change. As Marcus points out concern for a catastrophic collapse of Greenland's ice sheet is based primarily upon the assumption that modern warming is anomalous, indeed unprecedented in the Holocene. This is a testable assumption.Response: "concern for a catastrophic collapse of Greenland's ice sheet is based primarily upon the assumption that modern warming is anomalous"
I don't get this sense in the peer-reviewed literature. The concern for collapse of Greenland's ice sheet comes from the fact that when the Earth was 1 to 2 degrees warmer than now, sea levels were at least 6 metres higher than now. These higher sea level weren't because temperatures changed quickly during the last interglacial 125,000 years ago but due to sustained warmer temperatures. -
Doug Bostrom at 13:18 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Wes, do you think we might agree that the Greenland icecap is not "relatively robust" in the sense that a human artifact with purposeful over-engineering built into its design is robust? Put another way, what leads you to believe Greenland's ice is so robust as to be unresponsive to small changes in its environment and controls? I suggest instead that all the actual evidence we've been shown-- are indeed recording now-- indicates that ice on Greenland is quite responsive to its surrounding conditions, does not in fact have any degree of "robustness" at all. The ice sheet is no larger or smaller than it must necessarily be in the context of its surroundings. Greenland's ice is not an engineered object. It is an emergent feature of its environment. What would be entirely surprising would be to find that as such it is somehow decoupled from its external conditions. -
SoundOff at 12:59 PM on 1 June 2010Could global brightening be causing global warming?
Possible typo. The paragraph beginning: “However, changes in cloud cover and absorbing aerosols also contribute to global brightening. …” would make more sense if was this instead: “However, changes in cloud cover and absorbing aerosols also contribute to global warming. …” -
wes george at 12:58 PM on 1 June 2010Latest GRACE data on Greenland ice mass
Daved Green: Most ancient people of Siberia buried their dead in mounds above ground. The Viking graves were buried in the church yard in their settlement which couldn't have been permafrost because they were dairy farmers. In post # 18 I tried to introduce evidence that the MWP was global in extent and as warm or warmer than today but it got snipped out by our moderator.... So I am reduced to saying only that because there is evidence that the MWP was as warm or warmer than today and no "tipping" point was reach causing the icecap to slip away as some have suggested it might, there is no reason to believe that it will do so today, other than a 7-year long scary-looking graphic in the 20,000 year history of the Greenland icecap. My own bias here is towards the conception of the Greenland icecap as a relatively robust interglacial feature of the Earth's geophysiology. If it were so susceptible to succumb to temp perturbations only very slightly higher than today it's unlikely to have survived the last 8,000 years so intact. -
Jim Eager at 11:36 AM on 1 June 2010Could global brightening be causing global warming?
Actually, I think global brightening *is* currently at work, although not at all in the way that Monckton means. Allow me to explain. Besides the now waning El Nino and the start of solar cycle 24, there is another factor in play this year that no one seems to acknowledge: In the wake of the prolonged global recession industrial aerosols have undoubtedly been reduced globally through normal attrition and reduced replacement emissions, resulting in lower levels of sulfuric acid aerosols. As we know, these aerosols reflect a portion of incoming sunlight back out to space, thus acting as a negative forcing, or cooling, that has been masking part of the existing enhanced greenhouse effect from elevated greenhouse gas concentrations. In other words, the blue Reflective Tropospheric Aerosols trend line in the above chart has risen so that it now offsets less of the green Well-Mixed Greenhouse Gases trend line. Of course, at the same time there is also likely a decline in the Black Carbon warming trend, but it is no where near as large as the Reflective Aerosol forcing. Thoughts? -
johnd at 10:27 AM on 1 June 2010Could global brightening be causing global warming?
It's interesting, and completely logical that at some point clouds feature at some point in debates of the various aspects of climate change. Spencer is one researcher who believes that it is here that cause and effect have been confused, and as noted above by Marcus of an opinion that global warming leads to a reduction in certain types of cloud cover, may turn out to be such a case, and instead the opposite, the reversal of cause and effect, the reduction in certain types of cloud cover, in particular boundary layer clouds, may lead to global warming. Lindzen may have been referring to high level clouds. This is one aspect where the layman after digesting the theories and formulas being bandied around, is in a position to judge for himself, in a limited way, if those theories and formulas correlate with what is being exhibited in the physical space he occupies on the surface of the planet. Granted he may not be in a position to quantify it as it applies globally, or extrapolated into the future, but if it does work in his limited space and time, then it cannot be discounted as being wrong in the extended more sosphisicated equations. -
Alexandre at 09:55 AM on 1 June 2010Could global brightening be causing global warming?
Marcus #17 Indeed, there´s this study pointing to that cloud positive feedback. Some of figure 1 could be consequence, and not cause, as you suggest... -
Marcus at 09:31 AM on 1 June 2010Could global brightening be causing global warming?
Oh, which brings me to another point. What's causing global brightening in this instance? Lindzen rightly pointed out that global warming could lead to a reduction in certain kinds of cloud cover (I've forgotten which kind, can someone help with that?) So isn't it possible that at least some of the global brightening seen in figure 1 is-in fact-the *result* of CO2 induced global warming-not the cause as Monckton claims? -
Marcus at 09:28 AM on 1 June 2010Could global brightening be causing global warming?
Alexandre, you're quite correct. Just as increased clouds reflect incoming short-wave radiation, they're also good at trapping outgoing long-wave radiation. This is why the net radiative forcing of clouds is actually very low (at least as far as I understand it). This was the basis of Lindzen's Iris Hypothesis-the idea that global warming will lead to a reduction in cloud cover over the tropics, thus allowing more IR radiation to escape to the outer atmosphere-thus acting as a net negative forcing on future climate change. Unfortunately, evidence from CERES showed that, for the tropics at least, that when you accounted for the increase in short-wave radiation getting in, the Iris effect had a very small, net positive impact on warming. -
Alexandre at 09:18 AM on 1 June 2010Could global brightening be causing global warming?
GFW #13 Well, you´re right, Figure 2 encompasses even shortwave reflection from albedo variation. Even so, the aerosol lines show their forcing becoming more intense (and negative) over the period 1983-2001. That´s not what I see in Figure 1, and I´d like to understand the apparent discrepancy. My first thought would be that I´m missing some relevant detail... ubrew12 #14 I´ve enough BS from Lord Monckton and I don´t even bother following the reasoning why he´s wrong. My goal here is to learn and understand John´s point, mainly. You said "moving the point of absorption from the atmosphere to the surface". Isn´t the aerosol effect mainly reflection of SW, instead of absorption of any kind? (as confirmed by the overall negative effect in Figure 2) What else is included in the net effect calculation that is missed by Figure 1? (regarding aerosol effect) And you mentioned "[clouds] also increases the amount of infrared radiation leaving the earth". Isn´t it the opposite? Besides the albedo effect, it prevents some IR moving up the atmosphere? -
Marcel Bökstedt at 08:48 AM on 1 June 2010Websites to monitor the Arctic Sea Ice
Riccardo> I understand that PIOMAS uses a black art known as re-analysis. It is described as "reanalysing historical data using state of the art models". It sounds like something a forcasting system like pips would not do, and it could make the piomas model more reliable? But to be honest, I don't know anything concrete about this, I'm just improvising. -
Peter Hogarth at 07:45 AM on 1 June 2010Why Greenland's ice loss matters
Vinny Burgoo at 04:23 AM on 1 June, 2010 1) "They" are Stone, Lunt, Rutt, and Hanna and to quote from their paper "These simulations were run for time integration of 400 model years" 2) Yes, it's "in" peer review, reasonably common to cite papers in review, as long as you track any corrections or retractions. Your comments are rather unwarranted therefore. 3) I don't see the big deal in updating science/models with better data (some of the original bedrock and ice thickness data was more than thirty years old), and models (I would hope) get more accurate as we build up data to feed them. I cannot see how any rational person can imagine a model being less realistic with real observations and more recent data put into it. Some of the justification for Stone 2010 was that the reality of recent observed mass loss was more than the models were estimating, so the emphasis is warranted and "appropriate". I sense you should be backpedalling? -
scaddenp at 07:32 AM on 1 June 2010Empirical evidence that humans are causing global warming
Poptech - you might like to comment on the other 4 papers which also followed the idea of lets measure directly the radiation from the atmosphere since you think Evans is invalid? (And you are sure the conference didnt require review?). Now all of these papers involve measurement of the downward infrared. Do you contest that this measurement was made? Or that the measurement is invalid? The "model" used for interpretation is the RTE. Are you seriously implying that the equation derivable from QM and verified in lab experiments cant be trusted? Actually I would be interested to know what emperical evidence would change your mind. I am interested in how you understand "empirical evidence". -
shawnhet at 06:17 AM on 1 June 2010Working out climate sensitivity from satellite measurements
Chris, first off, I apologize for the remark about knowing what the linear striations mean. If you meant that they don't know what causes them physically, then you are consistent on that point, I suppose. IAC, can you do the math question I posted above? It involves an expression that you posted, so you should be able to do it. Once you do the math, it will be easy to see where you are going wrong. I won't need to keep repeating myself, I will just be able to point you to *the math*. If you can't do the math, I can walk you through it. -
chris at 05:55 AM on 1 June 2010Working out climate sensitivity from satellite measurements
shawnhet at 05:08 AM on 1 June, 2010 In fact Spencer and Braswell don't really understand the "linear striations" (as I've pointed out umpteen times now); e.g. they state:"Although these feedback parameter estimates are all similar in magnitude, even if they do represent feedback operating on intraseasonal to interannual time scales it is not obvious how they relate to long-term climate sensitivity."
and"Since feedback is traditionally referenced to surface temperature, extra caution must therefore be taken in the physical interpretation of any regression relationships that TOA radiative fluxes have to surface temperature variations."
and:"It is clear that the accurate diagnosis of short-term feedbacks – let alone long-term climate sensitivity -- from observations of natural fluctuations in the climate system is far from a solved problem."
You disagree strongly withe S&B and apparently feel sure that you know what the "striations" mean even if S&B don't. You're certain that they can be related to climate sensitivity in the commonly accepted understanding of the term (equilibrium surface temperature response to radiative forcing), when S&B explicitly caution against that extrapolation. Fair enough, but I don't find your assertions very convincing. Still, we can, if we want, make a preliminary assumption that the striations relate to a feedback parameter [f(s)]. If we do so, and parameterize a realistic climate heat capacity model with S&B's estimate of a possible f(s), we find (see my post just above), that the value of the climate sensitivity is rather little influenced by f(s). Since Lin et al (2010) [see citation in my posts above] have published this analysis, why not just look at their paper shawnet? -
Riccardo at 05:48 AM on 1 June 2010There's no empirical evidence
PaulK, Schwartz is the same as mine, you wrote it wrong. But anyways, if we agree that H indicates a variation and that your f(t) (apart from the sign convention) includes the forcing and the radiative thermal emission, we have an agreed starting point. You may not want to linearize the radiative thermal emission and write it as εσ(T^4-Te^4) throughout, but in this way you make the solution considerably harder to find. Afterall next term in the expansion is of the order of 10^-4, i'd say it's negligible. -
shawnhet at 05:31 AM on 1 June 2010Working out climate sensitivity from satellite measurements
Sorry, in the above expression fs should vary btw -3.3W/m2 (the non-existant feedback) and -6W/m2 under S&B. Plugging in 0 for fs will give the wrong answer. Cheers, :) -
shawnhet at 05:08 AM on 1 June 2010Working out climate sensitivity from satellite measurements
"Nope. You're saying stuff that simply isn't true shawnet." Frankly, this is tiresome. You, by your own admission, did not understand the central point(the linear striations) of the S&B paper, but you have been pontificating about it as though you are an expert. Since you like Lin's framework, I will show you how it works using that system. T (t→ ∞) = −F(t→ ∞)/(fs + fm)....Lin et al (2010) cited in a post above. Using, the above formula *hold everything constant except fs*, now vary fs. Start by assuming that it is nonexistant(ie 0) and then calculate what the value of T (t→ ∞) is when you change the value of fs to the value assumed by SPencer & Braswell. After doing that, then re-read my posts here. If you can do that and have further issues with *what I've written* I'll try and address them. Please refer to the answers you've gotten for T, as there is no point continuing this until I'm sure that you get the math. -
ubrew12 at 05:00 AM on 1 June 2010Could global brightening be causing global warming?
Figure 1 is solar at the surface. The text describes how some of this increased solar at the surface is due to reduced absorbed solar in the atmosphere (soot), and just moving the point of absorption from the atmosphere to the surface doesn't constitute 'global warming'. Also, some of this increased solar at the surface is due to a mechanism (clouds) that also increases the amount of infrared radiation leaving the earth. That is, the same mechanism cools as well as heats. Its the net effect, not merely the surface solar effect, that we should be measuring. Bottom line, just looking at the surface solar absorption is incomplete. Its cherry picking, which is probably why Monckton is doing it. Monckton is asking his listeners to, in effect, calculate the water level in a wooden tub by only considering the rate of water entering the tub, and ignoring the various holes in the tubs bottom. -
Vinny Burgoo at 04:23 AM on 1 June 2010Why Greenland's ice loss matters
Peter Hogarth, the Stone 2010 study doesn't show that 'we now probably have a more realistic model' It comes close to implying that but let's wait until it's finished passing through the peer-review process. I mentioned the other issues here on SS. (JC, to his credit, swiftly removed the links.) -
Tom Dayton at 04:19 AM on 1 June 2010Empirical evidence that humans are causing global warming
Poptech, Following up on Riccardo's reply, you need to realize that a model is inherent in even an old-fashioned liquid-filled thermometer that is a glass tube attached to a wooden board on which are painted numbers. The numbers are the model. -
Vinny Burgoo at 04:16 AM on 1 June 2010Why Greenland's ice loss matters
Riccardo, an accurate paraphrase can be misrepresentation if essential context is left out. Is this what our host did? Here's his paragraph in full: Climate modelling of the Greenland ice sheet predicts eventual collapse of the Greenland ice sheet if CO2 levels go over 400 parts per million (ppm). We're currently at 392 ppm. At 400 ppm, they predict that over the next 400 years, the ice sheet will lose between 20 to 41% of its volume (Stone 2010). This is equivalent to roughly 1.4 to 2.8 metres of sea level rise just from Greenland. Three things. (1) JC used Stone 2010 to collapse 'eventual' to '400 years'.(Does anyone know who 'they' are?) Why? (2) Stone 2010 is still in the middle of the peer-review process, so what's it doing on a website that makes such a big deal out of peer-review? (3) The Stone 2010 findings about volume-loss weren't predictions. They came from low-resolution tests of the performance of models that had been re-tuned to make them work with more up-to-date data. -
GFW at 04:13 AM on 1 June 2010Could global brightening be causing global warming?
Now that four people :-) have combined for a thoughough answer to RSVP, let's think about Alexandre's question. Ah, I see part of the answer. Figure 1 shows the combined effect of (apparently mostly aerosol) changes to incoming shortwave at the Surface. Figure 2 shows how each component affects the total (incoming & outgoing, all wavelengths) radiation budget at the Top-of-Atmosphere. So they aren't directly comparable. Nonetheless, Alexandre has a point because I don't see in figure 2 evidence for an actual *decline* in aerosols that would explain figure 1. Anyone? -
chris at 04:03 AM on 1 June 2010Working out climate sensitivity from satellite measurements
shawnhet at 02:29 AM on 1 June, 2010 Nope. You're saying stuff that simply isn't true shawnet. It's very difficult to escape the interpretations from Spencer & Braswell's own words that their "linear striations" have no necessary relationship to climate sensitivity (enhanced earth temperature in response to radiative forcing). So their analysis has nothing whatsoever necessarily to do with climate sensitivity. It’s tedious to keep saying this, and I wish you would hunker down and read their paper before insisting on interpretations that S&B patently don't make. The equation you present "T3=T1*SF*LF" (what are "SF" and "LF"?) doesn't make any sense in the context of S&B's analysis. Even 'though S&B are not sure of the physical basis or significance of their "linear striations", we can make a model of the real world response to radiative forcing making the preliminary assumption that they (the "striations" relate to a fast response to forcing [f(s)]. An appropriate equation to estimate the temperature change arising from radiative forcing, incorporating both a fast feedback [f(s)] and a feedback term in recognition that the real climate system has an "inertia" or "memory" [f(m)] is of the form: T (t→ ∞) = −F(t→ ∞)/(fs + fm)....Lin et al (2010) cited in a post above. In this case realistic values of f(m) indicate that the climate sensitivity has rather little dependence on f(s). Lin et al show this directly, and state:"Changes in f(s) values directly affect our solutions of fm, but the effect of different fs values on total feedback coefficient ftot is small because the temperature and net radiation constraints force the modeled climate system to generate similar amounts of net heat and temperature increases to satisfy these boundary conditions. Thus, the basic conclusions about climate feedback and sensitivity would not be affected much by the choice of fs."
So even if S&B's "striations" relate to a fast feedback parameter (we don't know), and whether or not these "striations" have any relation to climate sensitivity (S&B say they don't necessarily have any), and even if we nevertheless model the climate response to forcing making the preliminary assumptionthat they can be used to parameterize a fast feedback [f(s)] , the effect on calculated climate sensitivities is small. And remember that the real world makes sense, shawnhet. Just as you can't simply invent equations out of thin air, nor can you invent phenomena out of thin air. You can't obtain a "perfectly sensible explanation of the real world", by inventing a non-existent ocean cycle effect (eg PDO) that magically creates thermal energy. If the PDO (or other "ocean cycle effects") are ocean cycle effects then they can't possibly contribute to secular surface temperature trends (persistent temperature rise) since they are cycles. We don’t have to “guess” at this, or pretend that we don’t know what we do know (“year zero science”!). These issues have been studied at great length. A recent study indicates for example that “ocean cycles” have made essentially zero contribution to the warming of the last 100-odd years. So like your equation, your "sensible explanation of the world" is simply incompatible with what we know of the real world. -
Riccardo at 03:22 AM on 1 June 2010Empirical evidence that humans are causing global warming
Poptech, I'm sure you don't realise the consequence of what you said. I can not immagine any measurements without a model, a simulation, some data analysis but the simplest ones. No modern experimental apparatus, no high tech gadget can be immagined without models and simulations of some sort. But maybe you don't know, if you shout the alarm in bold characters for a trivial background subtraction. It looks like you think that it's enough to push a button and magically the "measurements" come out. The age of Galileo and Newton is over, get real. -
Peter Hogarth at 03:10 AM on 1 June 2010Why Greenland's ice loss matters
Vinny Burgoo at 00:27 AM on 1 June, 2010 Stone 2010 updates the boundary conditions for modeling changes in Greenlands ice sheet with more realistic input data. Specifically bedrock and ice thickness, temperature and precipitation. They use as many recent real observations as possible. In doing so they discover that the modeling run steady state with the new boundary conditions overestimates the current amount of ice by 25% compared with actual observations. Re-tuning the model to obtain more realistic current ice levels and then projecting forwards in time under the 400ppm CO2 scenario, the revised model suggests greatly increased ice loss under all 5 parameter sets compared with the previous unadjusted model, which had “predicted” similar future ice volumes to today at 400ppm. In other words our previous best predictions (or model outputs if you wish to be pedantic) underestimated future ice loss under given conditions, and we now probably have a more realistic model. I’m not sure John has really used this paper out of context, but I’m guessing he’ll comment. If you have other specific cases of misrepresentation, it would be useful to point these out so that amendments can be made if needed. I certainly don’t mind being corrected if it is shown I’ve misunderstood something, and this is probable if I stray from my areas of expertise. I would also hope you adhere to the same critical standards when visiting other sites! -
Riccardo at 02:38 AM on 1 June 2010Why Greenland's ice loss matters
"Although not completely collapsed, the 400p pmv ice-sheets for Figure 12b-e are somewhat reduced in the north of the island, with a reduction in ice volume compared with the modern day ice-sheet volume ranging between 20 to 41%. However, the scenario in Fig. 12f shows almost complete collapse at 400 ppmv with a reduction in ice volume of 81%." this is what the paper says. It's self evident that there's no misinterpretation whatsoever. I find only one (irrelevant) inaccuracy in what John wrote, it's not in 400 hundred years. The paper says that the results shown are after 400 hundred years of model integration, which is not the same thing as 400 years from now. As for the referee's comment, you're largely off target. Stones as well as John here did not make any projection of our future, as the referee advised. Both described what happens in a 400 ppmv world and none of them "predicted" a real world with a constant CO2 concentration at 400 ppmv for centuries. You may not like John's wording but the meaning is straightforward. Although not relevant in this particular case, i agree that research papers are often treated very badly around in the blogsphere. -
Alexandre at 02:38 AM on 1 June 2010Could global brightening be causing global warming?
I did not follow the point. Shouldn't the increase shown in Figure 1 somehow appear in the aerosol lines of Figure 2? Where did I understand it wrong? -
shawnhet at 02:29 AM on 1 June 2010Working out climate sensitivity from satellite measurements
"ONE: Your first point is confused isn’t it? One the one hand you say: ”S&B (and I)are not talking about the long-term feedback response (ie climate sensitivity),…” ...which we can all agree with, since that’s obvious by reading the paper and Spencer and Braswell (S&B) state this explicitly. But then you say: ”However, for a given set of long-term feedbacks S&B predict a less sensitive climate than if short term variations are governed by noise(in S&B's terms).” Respectfully, Chris, it is you who is confused. Let's say we have a forcing that instantly raises the temperature(T1) by 1C. Under S&B, that instant feedback is then acted on by a feedback(SF) that drops the temperature by 0.5C(T2), finally T2 is acted on by a series of long-term feedacks(LF) that multiply it by 3 ie T3=T1*SF*LF. Think about it. If SF is <1, then T3 *must be* less than if SF=1 *where everything else is equal*. Hopefully, now, you can understand where S&B are coming from. " The real world makes sense. In much the same way that a paper can’t at the same time be about climate sensitivity and not be about climate sensitivity, so the climate sensitivity (let’s say the Charney climate sensitivity) can’t be both significant and insignificant at the same time. The earth’s climate as it stands now does respond to enhanced radiative forcing with a surface temperature that rises to a new equilibrium compatible with this forcing. This sensitivity cannot at the same time be very small (~0.5 oC of warming for a radiative forcing equivalent to 2xCO2) and considerably larger (~2-4.5 oC of warming for 2xCO2)." Just FYI, now that you hopefully understand what S&B are saying, there is no contradiction btw assuming a short-term feedback of 0.5C to CO2 forcing, which is **then** multiplied by 2-4.5 by long-term feedback effects. If you combine such a framework with an ocean cycle effect(eg PDO), you have a perfectly sensible explanation of the real world. Cheers, :) -
Alden Griffith at 02:12 AM on 1 June 2010Could global brightening be causing global warming?
Here's my analogy of Monckton's logic: We can think of Monckton's attempt to calculate climate sensitivity from Pinker's 1983-2001 data (http://www.youtube.com/watch?v=og_Bu2zO61g&feature=related) as similar to trying to calculate an automobile's average speed over an entire trip. The problems are that (1) Monckton is estimating the average speed only from the tiny amount of time in which the car actually passes him by (the 1983-2001 period) instead of looking at a longer portion of the trip, and (2) he is forgetting that he too is also in a moving car (not including other opposing radiative effects of clouds and aerosols)! So how much can you say about the average speed of a car from point A to point B by watching it briefly pass you by and forgetting that you are also moving too? Zippity Dooda! Nothing! As Tamino so nicely put it, "if you can't convince them with logic, dazzle them with BS." -
Jim Eager at 02:04 AM on 1 June 2010Could global brightening be causing global warming?
Think CO2e, RSVP. CH4 has gone up by 150%, N2O by 15%. CFCs and other purely engineered chemicals did not even exist. -
Sean A at 01:57 AM on 1 June 2010On temperature and CO2 in the past
Gallopingcamel, are you saying that CO2 doesn't cause warming? You may want to check out a few of the other pieces of the puzzle, for example some recent posts here. Over these timescales, warming increases CO2 which causes more warming: The significance of the CO2 lag Has the greenhouse effect been falsified? -
Vinny Burgoo at 00:27 AM on 1 June 2010Why Greenland's ice loss matters
JC: At 400 ppm, they predict that over the next 400 years, the ice sheet will lose between 20 to 41% of its volume (Stone 2010). Stone 2010 doesn't predict anything. It is an investigation of current deficiencies in ice-mass modelling, not a crystal ball. Referee Comment C194 puts this better than I could: You don’t draw any direct conclusions about the future of the Greenland Ice Sheet from your modelling, and I think this is important not to do that. The conclusion of your work should relate to the model and not to the Greenland Ice Sheet. You have shown that the model is very sensitive to parameters, and hence any conclusions drawn from it about the future of the ice sheet itself should be seen in the light of this sensitivity and the model deficiencies. Otherwise it would be easy for someone to take Fig. 12f, in particular, out of context, to show that Greenland may not exist in a 400ppmv world. You weren't quite that bad. You took Fig. 12e out of context (41% versus 81% loss). Bad enough, though - and, in my experience, entirely typical of how research papers are treated around here. I think this is the fifth misrepresented paper I've found at Skeptical Science. I don't visit very often and I click on very few of your linked references, so five is a worryingly high number, especially as Skeptical Science is widely promoted as a source of balanced and authoritative information. In my experience, it isn't.Response: Vinny, I try to be balanced and accurate in how I represent papers but I've never said I'm infallible. But if I do make errors, I always correct them, I publicly admit my errors as I have done in the past with you and endeavour to not repeat the error. My primary goal is to further an understanding of climate by communicating the full body of evidence - misrepresenting the science is the last thing I want to do.
In this case, I think it's a reach to say Stone 2010 is just about modelling therefore its inappropriate to talk about the model results. While there is still much work to be done on modelling the Greenland ice sheet, does that mean we're not allowed to talk about the model results until they're perfect? In any case, I'm attempting to represent the paper as written, not the comments of that referree's comment. I will point out also that I chose to describe their best case scenario, not the worst case - a bit of IPCC-like conservatism on my part.
But the broader point here is that the Stone 2010 paper is just one result among many. There is also an empirical result (the paleoclimate study on over 6 metres sea level rise in the last interglacial), a semi-empirical result (mapping sea level rise to temperature to predict 75cm to 180cm by 2100. There's an alternative method of modelling glacier dynamics that finds sea level rise of 80 cm to 2 metres by 2100. These papers all use independent methods to arrive at the same conclusion - that Greenland is highly sensitive to sustained warmer temperatures and we can expect it to contribute significant sea level rise over this century and beyond.
So while I appreciate your feedback about Stone 2010 - especially the fact that it has yet to be approved of which I wasn't aware of - can I suggest you don't lose sight of the bigger picture and that you survey the full body of evidence before coming to any conclusions of where Greenland is headed. -
Daved Green at 23:34 PM on 31 May 2010Latest GRACE data on Greenland ice mass
wes george@18 I saw a Documentary on people living in siberia where to bury their dead they melted the permafrost with fire so they could dig a hole , they had to take turns working outside of 15 mins becuase it was so cold , maybe this is what the vikings did ? -
Arkadiusz Semczyszak at 23:23 PM on 31 May 2010On temperature and CO2 in the past
How can we be wrong about the valuation feedback, I again recommend: Interglacials, milankovitch cycles, and carbon dioxide, (Marsh, 2010) -
Arkadiusz Semczyszak at 23:20 PM on 31 May 2010On temperature and CO2 in the past
"In particular, during the warm periods the climate sensitivity is higher than average. In other words, the temperature increase produced by a forcing is higher when the system is in its warm phases." This assertion seems to be contrary to the basics of Eco-cybernetics. If we treat the Earth as a global Ekosfera complex system - with specific boundary conditions, the addition of energy to stabilize it. It is "richer" in energy - "can afford" to run, to strengthen the equivalent feedback - the more stable equilibrium. Yes because of the slowness of action of some feedback, greater stability of the system warm can be seen only over longer periods of time. For example, biocenosis "warm" are more biodiversity, which stabilizes ecosystems (generalizing - The diversity-stability debate, McCann, 2000). In this way, they (the biocenosis - ecosystems), one of the elements stabilizing the climate. "In the previous interglacial (the Eemian), there was a huge overlap between temperature increase and CO2 increase, which makes it near impossible to know the two-way influences. ..." "... professor Jianli Chen of the University of Texas also found that in a previous inter-glacial period called the Eemian, global temperatures were 6C higher than today, with CO2 levels roughly the same." ... the same - why? -
Ken Lambert at 22:58 PM on 31 May 2010Robust warming of the global upper ocean
kdkd #69 Is 16 years of "Robust" global upper ocean warming - which is the subject of this blog; regarded as climate or weather kdkd? If it is climate, then BP and I have illustrated that the large jumps in OHC before 2004 are calibration offsets of the XBT-Argo transition, and most probably illusory. If it is weather 'noise' then the same conclusion applies - not 'robust' but illusory. -
heather stevens at 22:52 PM on 31 May 2010How you can support Skeptical Science
thank you thank you thank you for existing! This site is fantastic. I have enough sense to know that global warming is occurring, but not the technical knowledge to often back up a discussion with a climate change denier. Thanks to this site i'm now armed with a bit more techy detail and will refer my family and friends who are unsure about GW to this site. thank you! heather Assessing the Risk from Sea Level Rise - Climate Change Impact Assessments -
chris at 22:31 PM on 31 May 2010Working out climate sensitivity from satellite measurements
A slightly broader assessment of S&B(2010) “Year zero science” [*]. It’s a little unfortunate to have to consider this, but it’s also sad that the efforts by scientists working in this area are apparently of effectively zero import once a couple of “celebrity crowdpleasers” enter the arena. The studies of Spencer and Braswell (2010) [and Lindzen and Choi (2009)] are two out of dozens of papers that address TOA radiative transfer, and the issue of estimating climate sensitivity from short term radiative response to temperature fluctuations (e.g. see papers cited in John Cook’s top article and here). Outside of proper science forums and quality science blogs (like this one), all of that other work is essentially invisible. Much like Lindzen and Choi (2009), S&B(2010) is already building up a head of blogsphere “steam” and if one looks at the presentations on the subject at a curious climate change politicisation get-together in Chicago a couple of weeks ago, for example, one might think that L&C and S&B is the entire science on this subject! In fact L&C(2009) is the only study that S&B(2010) explicitly refer to as support of one interpretation of their “analysis” [S&B state ” This is similar to the feedbacks diagnosed by Lindzen and Choi [2009] from interannual variability in recently recalibrated Earth Radiation Budget Satellite data…”]. And yet the analysis of Lindzen and Choi (2009) has been shown to be horribly flawed (see top article of this thread). Pretending that the wider science doesn’t exist and that the subject can thus be interpreted in its entirety through a couple of flawed analyses isn’t a good way to understand scientific issues! The real world makes sense. In much the same way that a paper can’t at the same time be about climate sensitivity and not be about climate sensitivity, so the climate sensitivity (let’s say the Charney climate sensitivity) can’t be both significant and insignificant at the same time. The earth’s climate as it stands now does respond to enhanced radiative forcing with a surface temperature that rises to a new equilibrium compatible with this forcing. This sensitivity cannot at the same time be very small (~0.5 oC of warming for a radiative forcing equivalent to 2xCO2) and considerably larger (~2-4.5 oC of warming for 2xCO2). Since (outside of “year zero” “philosophies” of “science”) there is a rather large scientific evidence base that supports the latter climate sensitivity, one needs to provide some strongish evidence if one wants to make headway with scenarios of low climate sensitivity. Likewise if one wishes to pursue very low climate sensitivities, one really needs to explain their fundamental incompatibility with real world observations. After all the rise in atmospheric [CO2] since the mid-late 19th century (290 then to 390 ppm now) is associated with a global temperature rise of 0.8-0.9 oC. We know that the earth’s temperature hasn’t yet risen to the equilibrium temperature compatible with the enhanced greenhouse forcing. We know that atmospheric aerosols have offset some of this warming. And yet within a “year zero” philosophy where everything we know about the real world is thrown out in favour of a cherry-picked selection of data points or wild extrapolation from observations of “linear striations” we are “led” to believe that the huge rise in atmospheric [CO2] has only contributed ~0.15 oC of global warming during the last 150 years. So with all the aerosols we've pumped into the skies the world really should have cooled somewhat during this period, polar, glacier and sea ice should have expanded somewhat, and sea level rise stopped or even started to reverse. Something doesn’t add up…. [*]”Year zero science” could also be termed “clean slate science”, and refers to the “philosophy” whereby a single measurement or analysis is created or selected, and publicised as if it constitutes the essential evidence that bears on a subject while pretending that the wider knowledge base doesn't exist.
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