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Tenney Naumer at 23:42 PM on 27 May 2010Why Greenland's ice loss matters
The mass balance loss curve is very likely to have steps in it from time to time. Recently, data show that melt run off is half of the loss. As the edges of the ice sheet recede, so too will the glaciers, and they will become less of a factor. Have a look at the ancient inlets all around Greenland. They do not taper to points at their ends. It seems to me that their blunt, squared-off, wedge-shaped ends were formed from meltwater pouring down from massive and very high waterfalls in ancient times when the ice sheet was much much larger and higher (I'm going out on a limb with this one). Also, has anyone noticed all the melting going on up and around the ice stream that feeds into the end of the Jakobhavns Glacier? It is so bad that it is creating its own clouds of vapor. Temperatures just to the south have been in the mid 60s. This year, the edge of the ice sheet already appears to be receding fairly rapidly all along the mid-west to north-west coast. -
thpritch at 23:38 PM on 27 May 2010The significance of the CO2 lag
While CO2 levels may lag temperatures in the Vostok ice core samples, this only indicates the state of the climate in the extreme Southern Hemisphere. Lea's paper in 2003 [1]compares the Vostok CO2 data against proxy data for the Pacific SST. His conclusion - "The strong correspondence of a proxy SST record from the eastern equatorial Pacific and the Vostok CO2 record suggests that varying atmospheric carbon dioxide is the dominant control on tropical climate on orbital time scales. This effect is especially pronounced at the 100 000-yr cycle." This tends to support Caillon's hypothesis (post 33) that the changes in the Earth's orbit relative to the sun initially caused the greatest warming in Antarctica with little to no warming in the tropics and Northern Hemisphere. The warming of Southern Ocean caused the release of CO2 which accelerated the warming of the Southern Ocean and started the warming of the tropics and Northern Hemisphere. -
James Wight at 23:31 PM on 27 May 2010Robust warming of the global upper ocean
John, have you considered updating the ocean cooling page? -
carrot eater at 23:18 PM on 27 May 2010Why Greenland's ice loss matters
When you think about scale, one must consider what is being discussed. If the question is, how long before Greenland has disappeared, or is half missing, then yes, a very very long time. If the question is, is this another line of evidence of warming in that region? Then the topic of lifetime is not so relevant. If the question is, what does this mean for sea level rise in the next 100-200 years? Then the scale here is not negligible. -
Ned at 23:03 PM on 27 May 2010Greenland rising faster as ice loss accelerates
HumanityRules, like the IPCC AR4 sea level rise projections, that paper doesn't attempt to include discharge of ice by marine-terminating glaciers. Its mass balance estimates are based solely on precipitation vs surface melt. This is the same problem that people have been discussing ever since IPCC AR4 came out -- their projections of sea level rise do not include ice discharge and are thus far too low. There are some further issues with the paper HR cites (they don't include several other factors that increase the rate of ice loss, and their model doesn't deal with spatial variability across Greenland -- they themselves point out in the paper's Discussion that this means their estimates of negative mass balance may be too low). So, it's not an uninteresting paper, but its projections of sea level rise are obviously incomplete. I am a bit surprised that they didn't say anything about the fact that their "-300 GT/year mass balance" prediction for 2100 has already come true by 2009-2010. -
Ned at 22:32 PM on 27 May 2010Why Greenland's ice loss matters
Chris's comment above is very insightful. Climate is determined by the earth's radiation balance and the fluxes of energy among components of the climate system. Under some conditions these fluxes create pseudoperiodic "cycles" that we give names like ENSO, PDO, AO, etc. but these are really just manifestations of internal variability within the climate system at particular spatial and temporal scales. Compare the temperatures during recent El Nino episodes. The 1982-1983 and 1997-1998 Ninos were much larger than the 2009-2010 one (both in duration and in magnitude of the peak, e.g. as represented by NINO3.4 anomaly). But 2009-2010 temps are much higher than those in 1982-1983, and rival those of 1997-1998 (slightly lower in the lower troposphere, slightly higher at the surface) despite being a far weaker El Nino. In other words, natural variability such as ENSO is superimposed on a long-term warming trend from greenhouse gases. A small ENSO peak today produces temperatures comparable to a big ENSO peak in the 1990s, and much warmer than a big ENSO peak in the 1980s. -
Berényi Péter at 22:01 PM on 27 May 2010Why Greenland's ice loss matters
#9 Arjan at 20:13 PM on 27 May, 2010 What about other glaciers? Click on image or just here for an overview of ancient literature. -
Ned at 21:36 PM on 27 May 2010Why Greenland's ice loss matters
The recent acceleration of the loss of Greenland's ice mass (increasing at 11% per year, doubling in 7-8 years) is obviously unsustainable. If that continued there would be no ice left in Greenland by 2075. There's no proposed physical mechanism by which that mass of ice could be ablated from that landscape in that time. But even a much smaller loss of ice on the century timescale would be economically and socially problematic. If Greenland lost only 10% of its ice, that translates to 0.6-0.7 m sea level rise on top of the sea level rise from thermal expansion, loss of mountain glaciers, and loss of Antarctic ice (so well over a meter of SLR total). In other words, even a trend much less extreme than that of the past decade would yield much higher rates of SLR than the overly cautious IPCC projections, which don't include dynamical changes to ice sheets. -
Berényi Péter at 21:34 PM on 27 May 2010Has the greenhouse effect been falsified?
Funny. It looks like absorptivity of CO2 in the 14-16 μm band is so high that in this frequency range air is opaque even at a 20 km altitude. Therefore measurements taken from aircraft around 15 μm only show the temperature of air nearby. This is why tropical Western Pacific (Fig 8.3 c) is warmer than expected there. However, proper high resolution molar absorptivity spectra for carbon dioxide mixed with dry air, measured in a controlled lab environment at different pressures from sea level down to perhaps 10 Pascal in tabular format (no pictures) would be appreciated. With these data at hand carbon dioxide photosphere altitude could be computed as a function of frequency. BTW, I can't believe it is not done already. A pointer, anyone? -
Riccardo at 21:27 PM on 27 May 2010Has the greenhouse effect been falsified?
Berényi Péter, because you used temperature profiles which are not the real ones, let alone the ones in that particular place and particular moment when the measurements were taken. Then even if you reasoning is right i do not expect it can be shown in this way. -
FerdiEgb at 21:01 PM on 27 May 2010Why Greenland's ice loss matters
chris at 20:27 PM on 27 May, 2010 As far as I know, ice melt at the Greenland edges is mostly a matter of (summer) temperatures. It has been warmer in the period 1935-1950 (with a loss of 70 meter ice in height) around the ice sheet edges than in the past 10 years. Several stations in Greenland have data since 1880 and show a periodic behaviour with a length of about 40 years for cold(er) and warm(er) periods. There is no significant trend in the Greenland temperature data over this 130 year period. Thus extrapolating the Greenland ice melt from data over the past 10 years is not warranted. That is also the case for global warming: part of the warming/sea level over the period 1970-2000 is certainly from natural variability (PDO, NAO, AO,...), which have some similar periodicity, while all warming of that period is attributed to CO2 by the models. But no model shows the influence of any known natural cycle with a periodicity between 1 and 100 years. This makes that all models overestimate the effect of CO2 and can't explain the halt in warming over the past decade. The current global temperature is already at the lower end of all projections (except for the brief El Niño period, which is at its end now). -
chris at 20:52 PM on 27 May 2010Why Greenland's ice loss matters
Arjan at 20:33 PM on 27 May, 2010 I think that's a reasonable point Arjan. There is still lots of uncertainty about ice sheet dynamics, the factors involve in acceleration of glacier outflow to the seas and so on. It is possible that the Greenland ice sheet has several metastable states, the transition from one to another perhaps occurring rather quickly. So we can't rule out the possibility that we're seeing an acceleration of ice loss which will stabilise at some new state of reduced mass (e.g. perhaps when a particular region/volume of vulnerable ice has melted). As far as addressing that specific point I think we probably need to defer to expert knowledge. -
skagedal at 20:33 PM on 27 May 2010Why Greenland's ice loss matters
Just quickly pointing out that his last name is spelled "Eschenbach". Thanks for the post.Response: Fixed, thanks. -
aj1983 at 20:33 PM on 27 May 2010Why Greenland's ice loss matters
I do however agree that, though the increasing rate of mass loss is worrisome, it (the acceleration) is hard to tell if this is temporarily or not because we do not understand the mechanism behind it well, and the measurement series is rather short. -
chris at 20:27 PM on 27 May 2010Why Greenland's ice loss matters
FerdiEgb at 17:38 PM on 27 May, 2010 "Extrapolating a trend from a cyclic behaviour is quite triggy..." No one is "extrapolating a trend from cyclic behaviour". Variation of Greenland temperatures/ice sheet mass balance through the Holocene has no element of "cyclic behaviour" (other than the very long term Milankovitch influences whose high N. hemisphere forcing resulted in high N. hemispheric warming around 9000-7000 years ago - this should be causing the Earth to cool achingly slowly now). The ice sheet varied according to variations in forcings and heat transfer, and the effects can be understood in relation to causes. So we certainly don't look at historical variations of climate phenomena (temperature/ice sheet/heat transport/sea level or whatever) arbitrarily call these "cyclic" and then pretend that that's an "explanation". Variability has accessible explanations in relation to known physics. That's why we can make projections of future behaviour based on empirical observations and theoretical knowledge. It's very difficult to escape the strong evidence that polar ice mass balance and its rate of change, and the resulting effects on sea level variation, are strongly linked to global temperatures (see references cited here here). -
Berényi Péter at 20:23 PM on 27 May 2010Has the greenhouse effect been falsified?
#59 Riccardo at 17:22 PM on 27 May, 2010 for good reasons Specify those reasons, please. -
CoalGeologist at 20:19 PM on 27 May 2010Why Greenland's ice loss matters
Berényi Péter @7: One thing new "under the sun" (unfortunately) is another 100+ ppm CO2.... (and by "new" I mean post-Ecclesiastes!). -
aj1983 at 20:13 PM on 27 May 2010Why Greenland's ice loss matters
@B. Peter: And how does the total area compare to today? What about other glaciers? -
CoalGeologist at 20:06 PM on 27 May 2010Why Greenland's ice loss matters
Peter Sinclair's Climate Denial Crock of the Week for April 11 includes an informative discussion of the mass loss of the Greenland ice sheet vis-a-vis "skeptical" arguments (in "Debunking Lord Monckton, Part One"). Discussion of Greenland begins at 5:50. The power of any scientific theory is to explain what we observe, and to predict what we have not yet observed. Climate scientists are making their best effort to anticipate future trends, but there will always be uncertainty. Thingamadonta @3 & FerdiEgb @2, the term "Climate Optimum" is value laden. It may have been optimal for some species, but surely not for woolly mammoths (among others). In any case, circumstances were quite different then, with continental glaciers still receding, sea levels considerably lower (stablizing at near current levels ~4,000 B.P.), Venice and New Orleans still in the planning stages, etc. In any case, warming at that time was apparently confined mostly to Arctic regions. Global temperatures are interpreted to have been cooler. We can't assume that contemporary warming will lead to "optimal" conditions. -
Berényi Péter at 19:54 PM on 27 May 2010Why Greenland's ice loss matters
#2 FerdiEgb at 17:38 PM on 27 May, 2010 In the period 1935-1950, the break-up point of the largest glacier was moving upward as fast as today From the 1920s on. Indeed.
The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun. Is there any thing whereof it may be said, See, this is new? it hath been already of old time, which was before us. There is no remembrance of former things; neither shall there be any remembrance of things that are to come with those that shall come after.
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Riccardo at 19:44 PM on 27 May 2010Why Greenland's ice loss matters
crhiscanaris, immagine to have a pot of water sitting in equilibrium on a spring on a slowly subsiding land; the pot will go down with the land. Then you start draining water from the pot, the spring pushes the pot up and the result will be that the pot will slower motion downward or even reverse direction if you drain fast enough. Not sure if this analogy makes it clearer. -
Riccardo at 19:31 PM on 27 May 2010Why Greenland's ice loss matters
thingadonta, models do not extrapolate current behaviour. They project on the basis of scenarios, not extrapolations. -
chris1204 at 19:21 PM on 27 May 2010Why Greenland's ice loss matters
Returning to an earlier post, I still haven't got a good sense of why Greenland seemed to be in a state of decelerating rebound (sinking?) around 2003 if ice was melting at an accelerating rate. Apologies if an answer has been posted which I've overlooked. -
thingadonta at 18:21 PM on 27 May 2010Why Greenland's ice loss matters
You mention that "Extrapolating an accelerating curve into the future is always problematic." But isn't this what all the IPCC future climate projections do? These very 'problems' are what skeptics are concerned about. Another point, wasn't the early Holocene also 1-2 degrees C warmer than now? I think Eschenback is making a point that minute Greenland ice losses are sometimes reported as something large and worrisome right now, rather than if they continue to accelerate. It's ony going to be a major problem if the 'extrapolated acceleration curves' of the IPCC turn out to be correct. -
Riccardo at 17:59 PM on 27 May 2010There's no empirical evidence
PaulK, the process you describe is just an integration, which we already know. In some cases, like for example the linear forcing, we have the analytic solution. For a more general forcing we need to do it numerically. And we agree on this. But then you confuse the forcing with the OLR and never in you analysis does the net balance appear. Indeed you write dH/dt=-f(t); here f(t) should be the net energy (im)balance but then it cannot be equal to the OLR. You need to have both the forcing and the thermal radiation. I'd suggest to first write and solve the heat balance equation for ΔT (sorry if i keep using variations, why bother with the equilibrium values?). After that we can try to see who's that guy we call OLR. -
PaulK at 17:47 PM on 27 May 2010There's no empirical evidence
Doug, Looking back at my posts, my attack on the article in the Open Mind site was completely ill-founded, and I retract my comments unreservedly. I claim temporary insanity since I was in the grip of an obsession that led me to believe incorrectly that Riccardo was using the Open Mind article to support an invalid definition of the forcing term as used in the Schwartz model. The author's reputation for infallibility remains untarnished - at least by me. -
FerdiEgb at 17:38 PM on 27 May 2010Why Greenland's ice loss matters
One need to take into account that the "accelerating" ice loss of Greenland's ice sheet is based on only a decade of accurate satellite measurements. But Greenland shows a quite different climate behaviour, compared to other parts of the world. In the period 1935-1950, the break-up point of the largest glacier was moving upward as fast as today and with a lot of ice loss at the ice sheet edges. After 1950, the glacier break-up point advanced again until the late 1990's. If one compares the summer temperatures around Greenland, these were higher in the previous period than today... See: http://www.ferdinand-engelbeen.be/klimaat/greenland_temp.html Some 6,000 years ago, the ocean north of Greenland was (at least in summer) ice free, due to higher temperatures (the Holocene optimum). Extrapolating a trend from a cyclic behaviour is quite triggy... -
ubrew12 at 17:26 PM on 27 May 2010Why Greenland's ice loss matters
Comparing 2009's loss to the entire sheet is, perhaps, apples and oranges. Compare the 2009 loss to the loss needed to raise sea levels by 1m, which is 14% the size of the entire sheet. Then, project the loss from 2029 onto the same block diagram, to give a visual of the acceleration. Just a thought. -
Riccardo at 17:22 PM on 27 May 2010Has the greenhouse effect been falsified?
Berényi Péter, you did it again. You used a descriptive graph and said that it's sylas that should provide more details. Even a superficial look at your graph in comment #56 should evidence that it's not worth any quantitative comparison with actual data. And indeed, of the three environments (out of the four spectra shown) two do not much your expectations, and for good reasons. -
Doug Bostrom at 16:23 PM on 27 May 2010There's no empirical evidence
I'm not sure I see where the problem is regarding TOA imbalance, model versus observations (observed OLR vs. IPCC assumptions?). After cleaning up some obvious problems (>6W/m2, we'd cook more rapidly) with satellite measurements, we're left with direct imbalance observations of ~0.95W/m2 versus model predictions of ~0.85W/m2*. These rates are in reasonable agreement. I see PaulK's point w/regard to his formal look at the situation but something's not quite closing the circle; we can quibble about splicing etc. but it's pretty hard to simply say -all- OHC and atmospheric temperature measurements for the past 40 years are wrong and that temperature has not changed in that time, meanwhile both models and observations indicate an imbalance. Hmmm. A puzzle. *EARTH’S GLOBAL ENERGY BUDGET, K. E. Trenberth, J. T. Fasullo, J. Kiehl, Bull. Am. Meteorol. Soc. 90, 311 (2009) Full text here. -
Jeff Freymueller at 16:16 PM on 27 May 2010Greenland rising faster as ice loss accelerates
#58 Humanity Rules, you can take solace in the model prediction if you like, but the present rate of mass loss rate of 300 Gt/year is about 300 km3/year of ice (1 km3 of ice masses about 0.9Gt), and by my count there remain 90 years of warming in the A1B scenario to go before we hit 2100. Meaning that the model is massively underpredicting the rate of ice loss. My guess is that the model ignores glacier flow, but that's a guess based on a quick look at Fettweis' web site, which shows figures for melting and precipitation. This may also provide some context for wes george's question about why this is a big deal (#51). I also got quite a chuckle out of someone's claim (I forget who) that Science and Nature were somehow competing to publish "alarmist data". You must be joking! -
Jeff Freymueller at 15:55 PM on 27 May 2010Greenland rising faster as ice loss accelerates
#49 Humanity Rules, where did I say that the Earth as a whole was not losing ice over the last couple hundred years? I said GREENLAND was not. Now it is. That's a fundamental change. The blue diamonds on your figure may be the red squares on Figure 2 in John's original post. I prefer that other figure because it shows all of the independent estimates rather than a single source (and it lacks the overly squiggly "linear reconstruction", which is based on heaven knows what (not the observations!). Not to say that the general trend of that reconstruction is necessarily wrong, just that without a lot more information about how it was estimated, it shouldn't be assumed to be right, and its continuity is misleading. -
Ari Jokimäki at 15:50 PM on 27 May 2010Working out climate sensitivity from satellite measurements
A recently published paper by Lin et al. addresses Spencer's feedback determinations. The end result seems to be that Spencer is studying noise. This paper is also relevant to Lindzen's stuff. By the way, here's my take on Lindzen & Choi (2009). -
Doug Bostrom at 14:37 PM on 27 May 2010There's no empirical evidence
Apart from your semi-deplorable fling about "junk science" PaulK, may I just say how refreshing it is to see people such as you and Riccardo, "e" roll up their sleeves and invest some serious mental elbow grease here? There are only a few folks hanging out on the site who can have a conversation of this nature and produce reasonable repartee, particularly when it comes to doing maths; Riccardo, BP and a very few others come to mind. I'm not sure about the importance of the discrepancy you mention as a dilemma, I'm off to see what's up in the recent observational department on that but it's certainly pleasant to see such detailed treatment. -
HumanityRules at 14:14 PM on 27 May 2010Working out climate sensitivity from satellite measurements
I read the (Chung et al 2010) paper. Could anybody tell me what climate sensitivity he reports from the satellite data. If you can convert it to oC I'd be grateful. This might be the relevant passage if that will help. "The recomputed slopes after removing the estimate of the Pinatubo radiative forcing (open circles in Figure 1d) are generally between 1.25‐2.0 W m−2 K−1 and more similar to the values of the AMIP model simulations." They also state "The computed values are consistently smaller than the value of the no‐feedback case (3.3 W m−2 K−1)" -
Philippe Chantreau at 12:58 PM on 27 May 2010Collective Intelligence and climate change
HR, complete re-organization of the transport system is inevitable at some point. It's just a matter of doing it in a controlled way, rather then being forced to. -
PaulK at 11:19 AM on 27 May 2010There's no empirical evidence
Riccardo, I promised a post proving that the general solution I offered in #55 is easily reconciled with Schwartz if one accepts his assumptions. Generalised heating model: dH/dt = Q(t) – E(t) = absorbed SW (flux) – Outgoing LW(flux) at TOA Assume that at time t = 0, the system is in steady-state equilibrium: Q(0) = E(0). Now, keeping everything else unchanged, consider a positive impulse forcing F1 = constant which results in a perturbation, f(t), of the OLR. We can write: OLR(t) = Q(0) + f(t) ; Q(t) = Q(0) = constant ; dH/dt = -f(t) At this stage, we don’t know what f(t) looks like, but we do know some things about it: • Minus f(t) is positive definite on the open interval (0,te), where te is the equilibrium time. (Otherwise the (constant impulse ) forcing would have to cause a net cooling at some stage in its effect). • As the system restabilises at the equilibrium time, te, f(t) must go to zero. • It is both closed and integrable, since the area bounded by the curve represents the finite energy commitment associated with the impulse forcing, F1. This system can be solved for the total perturbation (and hence for OLR) by superposition. This permits one to model combinations of input and output forcings over time. But let us consider the simple case first of where we have an exponential or annually geometric growth in CO2, translated into a forcing which is linear with time: F(t) = bt. The solution is analytic for this condition, but for convenience later, we will choose a superposition timestep of 1 year. We set the first year forcing F1 = b. All subsequent years are then also equal to F1 to satisfy F=bt. This is equivalent to superposing each year the same perturbation function f(t) to obtain the total perturbation to the system. The solution is then OLR(t) = Q(0) + integral of f(t) from 0 to t for all t< te OLR(t) = Q(0) + integral of f(t) from 0 to te (i.e. a constant) for all t>=te Note then that independently of the choice/calculation of the perturbation function (f(t)), OLR is monotonically decreasing until the equilibration time, and stays constant thereafter for this case of F(t) = bt which is proxy for a geometrically increasing CO2 concentration. This is an analytic result. So, does the above solution work for the Schwartz model? In Schwartz, the equilibration time strictly speaking is infinity (NOT tau). The perturbation function for a constant impulse forcing F1 in Schwartz is given by f(t) = -F1*exp(-t/tau) = -b*exp(-t/tau) Substituting into the generalised solution for OLR above, we obtain: OLR (t) = Q(0) + integral of f(t) from 0 to t = Q(0) + b*tau*(exp(-t/tau) – 1) for all t less than te = infinity. You should then find that this is compatible with the solution we obtained directly from manipulation of Schwartz. Next stage is to better understand the difficulties of reconciling the increasing OLR with IPCC assumptions. -
HumanityRules at 10:33 AM on 27 May 2010Greenland rising faster as ice loss accelerates
Present and future climates of the Greenland ice sheet according to the IPCC AR4 models Bruno Franco1 , Xavier Fettweis, Michel Erpicum and Samuel Nicolay Climate Dynamics DOI 10.1007/s00382-010-0779-1 Abstract "......We also show that the GrIS surface mass balance anomalies from the SRES A1B scenario amount to −300 km3/year with respect to the 1970–1999 period, leading to a global sea-level rise of 5 cm by the end of the 21st century.........." 5cm would be less problematic. -
Doug Bostrom at 10:15 AM on 27 May 2010Working out climate sensitivity from satellite measurements
Thingadonta needs to go back to school. Basics of general circulation models. Free to read, no need to speculate. -
chris at 10:11 AM on 27 May 2010Working out climate sensitivity from satellite measurements
Berényi Péter at 09:02 AM on 27 May, 2010 "The paper is about short term water (vapor+cloud) feedback and they do find a low sensitivity here." No they don't Peter. I wonder whether you've read the paper. In a scientific paper your interpretations have to be consistent with the data you present and its analysis. In this case Spencer and Braswell fiddle around with various ways of plotting globally averaged anomalies in CERES net fluxes and find "considerable scatter". They try higher time resolution and find negative regression slopes (flux vs surface temperature) which they suggest cannot represent the real sensitivity. They try restricting the analysis to the global oceans (60 oN to 60 oS latitude) with daily resolution comparisons of flux with sea surface temperatures...however they find the correlations are negative. They try extending the time scales of intercomparisons (radiation flux and SST). They try phase space plotting of the data... Eventually they come up with "evidence of linear striations". These have slopes of around 6.2 W.m-2.K. Spencer and Braswell state: "These striations are significantly different from a similar plot of two time series of random numbers, shown in Fig. 3b, suggesting that the striations are due to some underlying physical process." Does that sound like they've "found low sensitivity here"? I don't think so. The paper has some interesting comparisons of a simplified model with GCM's. It's quite good at highlighting the difficulties of identifiying fast feedbacks in the presence of external forcinsg. What it doesn't present evidence of is "low sensitivity". Of course Spencer may say otherwise on his blog (a bad habit). But if you can't justify an interpretation in a scientific paper, then that interpretation is unlikely to be scientifically valid. -
Berényi Péter at 09:14 AM on 27 May 2010Working out climate sensitivity from satellite measurements
#13 chris at 08:17 AM on 27 May, 2010 Incidentally, it's worth looking at Foster and Gregory 2006 The paper is available here. -
Riccardo at 09:11 AM on 27 May 2010Working out climate sensitivity from satellite measurements
Chris G, did I say anything about the future? I just gave the "standard" definition of sensitivity which could in principle be used to evaluate it using past data. Maybe John's response to Alexandre #2 is clearer than mine. -
Berényi Péter at 09:02 AM on 27 May 2010Working out climate sensitivity from satellite measurements
#11 chris at 07:41 AM on 27 May, 2010 he (and Braswell) are quite explicit in stating that the parameter they pulled out of their analysis doesn't have any necessary realtionship to the climate sensitivity as it is commonly understood Of course they state that as it is true. The paper is about short term water (vapor+cloud) feedback and they do find a low sensitivity here. There may be any number of feedbacks operating on longer timescales, some of them strong positive. However, current computational climate models can't project much warming with no fast & strong positive water feedback. Here is an earlier presentation by the same authors on this topic, 16 December 2009 AGU Meeting, San Francisco, CA -
Berényi Péter at 08:47 AM on 27 May 2010Estimating climate sensitivity from 3 million years ago
FYI The Spencer & Braswell (2010) thing is continued here -
thingadonta at 08:44 AM on 27 May 2010Working out climate sensitivity from satellite measurements
Firstly, I think the above discussion is very good. A few points: The global data is too imcomplete to make a definitive conclusion about climate sensitivity, especially in the higher latitudes. However, most of the data I have seen does suggest the tropics don't warm as fast as other regions when the earth warms (which also means Hurricanes and Cyclones shouldnt increase in frequency with warming, because of the lower T difference and greater stability between the tropics and temperate regions). The papers looking at Earths history sensitivity, some of which you have presented on this site (eg Little Ice Age), are not definitive for climate sensitivity either. They are generally models which insert C02 to explain longer term trends, and leave out other factors, such as clouds and changes to ocean currents. The reason they 'converge' is because they use essentially the same causal explanations. They are not really that 'independent' (eg many papers refer to each other to provide eg back up to uncertainties in the data, like using the same dataset for proxy temperatures). Essentially, the models use the same assumptions to come up with the same conclusions. -
jimmck at 08:18 AM on 27 May 2010Human CO2 is a tiny % of CO2 emissions
You have referred me to "working out climate sensitivity by satilite measuements" as a response. While it is not conclusive on most points it is conclusive on the fact that no one has a handle on global sea temperatures. There seems to have been a concensus developed that average atmospheric temperatures have increased by 0.7C over the last century but there is none on average seawater temperatures. The reason I am interested is that on an holistic basis it seems that the solubility curve of CO2 would require the oceans to give up 4% of their CO2 for a 1.0C temperature increase. ie it would take a 0.03C increase in average seawater temperature from 2000 to 2010 to explain the 43Pg's/GT's increase of atmospheric carbon over that ten year period. -
chris at 08:17 AM on 27 May 2010Working out climate sensitivity from satellite measurements
Berényi Péter at 07:38 AM on 27 May, 2010 if......if...... I suspect the fast feedbacks will be found not to be negative, Peter. All the dodgy attempts to winkle out something with the appearance of a negative feedback (flawed analyses by Spencer and Braswell, and by Chylek, and by Schwartz, and by Lindzen and Choi) have turned out to be scientifically deficient. In any case, there are a couple of obvious flaws to the notion that fast feedbacks are negative. The first of these relates to the numerous direct measurements of enhanced tropospheric humidity in response to atmospheric warming. It's very difficult to come to a conclusion that this (a) doesn't exist, and (b) isn't a positive feedback. The second is the observation that we've had around 0.8-0.9 oC of global warming since the mid-19th century. It's easy to calculate that a radiative forcing from the known enhanced [CO2] with zero feedbacks should give a warming at equilibrium of around 0.4 oC (see point (v) here). Since we know that we aren't yet near equlibrium with the current forcing, and that a substantial aerosol load has offset some of the warming from enhanced anthropogenic [CO2], and that solar variability has made no more than around 0.1 oC contribution to this warming, it seems very unlikely indeed that the feedbacks to [CO2]-induced primary atmospheric warming are not positive and substantial (one should also factor in contributions from black carbon and non-CO2 greenhouse gases). And that's without considering the abundant evidence from paleotemperature/[CO2] relationships that indicate a climate sensitivity near 3 oC of warming at equilibrium per doubling of atmospheric [CO2]. Incidentally, it's worth looking at Foster and Gregory 2006, which does a very good job of highlighting the issues associated with attempting to use direct measures of TOA radiation to estimate climate sensitivity..... Incidentally (b!) Spencer and Braswell certainly are not talking about Charney sensitivity. They state this explicitly in their paper (see my post just above and the link therein). Lindzen would like to "sell" the pretence that his analysis is about Charney sensitivity, but it turns out not be... -
Berényi Péter at 08:13 AM on 27 May 2010Has the greenhouse effect been falsified?
#57 Riccardo at 00:18 AM on 27 May, 2010 You can determine the temperature of the photosphere in the 14-16 μm range (CO2 stopband) comparing it to the blackbody radiation curves. As the atmosphere is absolutely opaque in this frequency range, it acts as a perfect black body here. As from photosphere height up it gets transparent fast, this black body radiation segment is seen above wit no attenuation. Approximate temperatures - Fig 8.3 a (Sahara Desert): 215 K (-58°C) Fig 8.3 b (Antarctic ice sheet): 197 K (-76°C) Fig 8.3 c (Tropical Western Pacific): 215 K (-58°C) Fig 8.3 d (Southern Iraq): 217 K (-56°C) Temperatures a & d are close to the respective tropopause temps. Temperature for b may be much colder than indicated for polar tropopause, but it must be during polar winter when tropopause drops to the surface. Temp c is warmer than expected, but troposphere temperature over the tropics is variable both in space and time (of day). Anyway, in that graph photosphere temperature in CO2 stopband is the same over clear sky and thunderstorm anvil. Therefore it should be above tropopause. -
Chris G at 08:04 AM on 27 May 2010Working out climate sensitivity from satellite measurements
Are Lindzen et al only talking about Charney sensitivity? I may have missed that; it sounded to me that their sensitivity estimates did not include caveats about assuming no ice surface area changes and no atmospheric composition changes, etc. OK, if you assume that there are only fast feedbacks and you can detect a reduction in the rate of energy flux, then you can make an educated guess as to where equilibrium will be reached. However, since they only used SST from 1985-1999, SSTs have changed a lot since then, the ice extent has change dramatically in the last decade, and the composition surely has not remained static, I don't see that these are realistic assumptions. -
chris at 07:41 AM on 27 May 2010Working out climate sensitivity from satellite measurements
Berényi Péter at 07:05 AM on 27 May, 2010 No I think we'll find that Spencer hasn't found anything of the sort Peter. In any case he (and Braswell) are quite explicit in stating that the parameter they pulled out of their analysis doesn't have any necessary realtionship to the climate sensitivity as it is commonly understood (i.e. the Earth surface equuilibrium temperature response to a radiative forcing equivalent to a doubling of atmospheric [CO2]). I described this in some detail here. I'm surprised you're commenting on a paper that you haven't read...
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