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Comments 118351 to 118400:

118351. CoalGeologist at 05:03 AM on 2 June 2010
        On the Question of Diminishing Arctic Ice Extent
        johnd @#17 I believe the difference you're noting relates to the formation of annual ice during the Arctic winter, versus the summer melting of this (thin) ice, plus the older thicker ice during Arctic summer. There will likely always be a thin layer of winter ice in the Arctic (unless warming becomes really extreme), but we appear to be moving toward a time in the not-too-distant future when the Arctic will be ice-free in the summer. (Time for Superman to seek a Fortress of Solitude in the Amazon rainforest.... Oops... May soon be too late for that as well.)
        Response: Wasn't the fortress of solitude at the south pole? :-)
118352. Gordon1368 at 04:59 AM on 2 June 2010
        On the Question of Diminishing Arctic Ice Extent
        johnd - The recovery for extent is mostly bounded by land mass, and mostly occurs in an area where there is little or no sunlight in the winter. So I don't see a problem with the recovery of extent filling the Arctic ocean area each winter, even as the ice thins and mostly melts in summers. Even this last winter, extent recovered quite well for a short period. So it may be a number of years before winter maximum extent falls as quickly as the summer minimum extent. But it looks like it is heading in that direction to me.
118353. Rob Honeycutt at 03:58 AM on 2 June 2010
        Update of Visualisations of Carbon Dioxide
        I have to say, Andy Jacobson has done an incredible job of creating a highly compelling graphic of historic CO2 levels. Just amazing. I saw his original version several months ago and this new version is that much better.
118354. johnd at 03:47 AM on 2 June 2010
        On the Question of Diminishing Arctic Ice Extent
        Something which appears to have been overlooked so far regarding the first graph which shows the sea ice minimum as decreasing faster than the sea ice maximum, and the expectation of the discrepancy between minimum and maximum to increase, is that for the gap to widen, the recovery rate, that is the amount of new ice each year, has to increase. Just to illustrate, the mean area for March ice for the period 1979-2009 is 15.8 million sq km, and the September mean is 6.7. This gives a mean recovery of 9.1 million sq km. The September 08 ice was 4.5, the March 09 ice 15.2, giving a recovery of 10.7. Hence, for the expectation that the discrepancy between the trends of min and max to increase to be fulfilled, the recovery rate of ice from the September lows to the March highs will also have to increase.
118355. cloneof at 03:13 AM on 2 June 2010
        Arctic icemelt is a natural cycle
        Is the graph from Stroeve 2007? I find it quite hard to read a graph that I don't know the source from.
118356. Argus at 01:30 AM on 2 June 2010
        On the Question of Diminishing Arctic Ice Extent
        Or rather, 14 years, not 20. And from 1995 to 2009, not 2005. Sorry!
118357. Argus at 01:27 AM on 2 June 2010
        On the Question of Diminishing Arctic Ice Extent
        #13 : muoncounter prefers to be ironic and make fun of my remark concerning the ocean temperatures graph. My point was certainly not that you can draw any conclusions about the climate from just 5 years of data. Yet the NOAA author sees (in the graph) a prominent shift toward warmer temperature from about 2000 to about 2004, but fails to see (in the same graph) an even sharper shift toward colder temperature in the following 5 year period. You see what you want to see. Looking at the whole graph, from year 1995 to 2005, we see that there is absolutely no change in 'Depth averaged temperature' at at the Mooring 2 location in the Bering sea. That is good, but 20 years of weather is still not climate.
118358. HumanityRules at 00:45 AM on 2 June 2010
        On the Question of Diminishing Arctic Ice Extent
        It seems that in a recent article on this website that 2007 stands outside the 'normal' downward trend due to climate change. Don't you run the risk of this anomalous year contaminating your analysis. I guess what I'm asking is what would the conclusion be if you ended the analysis in 2006?
118359. angliss at 00:05 AM on 2 June 2010
        Update of Visualisations of Carbon Dioxide
        Vulcan is an amazing product and I highly recommend visiting the site and playing around with their Google Earth/Maps overlays to see what's going on in the US in great detail. I live in the Denver, Colorado metro area, but looking around Colorado I found a couple of counties that seemed to have oddly high CO2 emissions - until I found that one is a favorite of off-road enthusiasts who drive high-pollution, inefficient snowmobiles in the winter and ATVs in the summer. The other is one of the most polluting coal plants (not just CO2, everything) in the country.
118360. muoncounter at 23:43 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        Thanks for the feedback. #1: "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." Good point, I'll check. #4: 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. ... Moreover, it's quite possible that the decline in March maximum might start catching up to the decline in Sept minimum" Doesn't 'decline in March' catching up with 'decline in Sept' require acceleration? As for the crystal ball of statistics, these data end in 2008; Sept 2010 isn't that far off. #9 and #11: "picking one temperature series from a bunch of islands in the Bering Sea seems a bit arbitrary." ... " example of selective analysis" Oddly enough, I originally plotted the pct ice change against a trend extracted from the land ocean temp index for latitude 64N-90N that I found here. That graph shows up in a comment on a prior article here. But I thought that was painting with too broad a brush. #11:"get the idea that ocean temperatures for the previous decade show a dramatic shift toward *colder* temperatures after 2004." I read somewhere that 'climate' requires a much larger time frame than 2004 forward. Some folks use 30 year statistics? From the temperature data (some going back to the 1890s) I've looked at, a 15 year trailing average is a great way to extract an underlying trend. There are outliers that are both above and below the trends on the September min ice graph. #12: The long-term trends on the graph posted by Peter Hogarth also speak to increasing rates of ice loss.
118361. Ned at 22:46 PM on 1 June 2010
        Latest GRACE data on Greenland ice mass
        JMurphy, wg was mistaken in this case, but it's certainly true that comments are deleted here, mostly for failure to comply with the comments policy. IMHO, it's the rigorous and even-handed enforcement of that policy that has kept this site readable while the number of visitors has skyrocketed over the past year. I'm not bothered by wg's claim that my comment was deleted; I'm bothered that he completely misinterpreted it ("that’s where I got the idea that someone here might possibly believe in the imminent failure of Greenland’s icecap....within our children's lifetime! Silly me.")
118362. JMurphy at 22:24 PM on 1 June 2010
        Latest GRACE data on Greenland ice mass
        wes george, your accusation that a post had "been modified over the weekend. Down the memory hole!", has been shown to be incorrect, as far as I can see. Therefore, I think it only fair that you should admit your mistake and take back the false insinuation you made against this site.
118363. Ned at 21:27 PM on 1 June 2010
        Latest GRACE data on Greenland ice mass
        Wes George writes: 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. Where do you get that "2080 to 2150" from? Pretty much all the emissions scenarios (except the obviously unrealistic "Year 2000 constant concentrations") give 1-2 C warming by the middle of this century. Don't make the mistake of just projecting forward the 0.8 C we've experienced so far -- even if we capped emissions right now (which isn't going to happen), the rate would increase beyond that 0.8C per century because of additional warming in the pipeline thanks to slow feedbacks.
118364. Ned at 21:13 PM on 1 June 2010
        Latest GRACE data on Greenland ice mass
        Wes George writes: There was a post on this site that suggested if these trends not only continued on this very short slope but accelerate exponential then Greenland’s icecap will be gone in 65 years! As Doug Bostrom points out, the comment of mine that you're referring to is right here. I thought the point was obvious -- extrapolating the past decade's accelerating rate of ice loss leads to a physically unrealistic result (all ice gone by 2075) and thus is unreasonable. There is no realistic process that could ablate that much ice from that physical setting in that short a time. My second point was that even a much slower acceleration than we're seen over the past decade would still have disastrous results. A much slower acceleration might leave 90% of Greenland's ice still intact in 2100, but would also contribute to a greater than one meter rise in sea level when combined with thermal expansion and loss of ice from West Antarctica and alpine glaciers. Sea level is one area where the IPCC forecasts have clearly been too cautious (see here and here).
118365. Peter Hogarth at 19:59 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        HumanityRules at 16:27 PM on 1 June, 2010 and of course Muoncounter! Thought you might be interested in some more Pan-Arctic Ice extent correlations with temperature, which I’ve been looking at for an Arctic post: SST and summer ice extent: some of the SST grid reconstructions can be biased as they set grid cells to -1.8 degrees where the ice is, so you have to use an ice area mask, or avoid areas where there is ice (I think?). I believe other work on Polar Pathfinder satellite SST data (good “dense” spatial coverage) is ongoing. This chart uses the ICOADS series which is based on raw on-site measurements: I can’t say exactly where the measurements are taken as yet, but there are enough of them in recent decades to be moderately convincing. Maybe someone with more expertise can comment. The choice of scale is arbitrary but the correlation is high. Other reconstructed (ERSSTv3, HadISST etc) series also display this correlation if you select ice free grid cells. You could also correlate HadISST ice and SST all the way back to 1870 with lots of caveats and caution. It would be interesting to look at Atlantic side and Pacific side separately, but I haven’t found time for a complete comparison. Air temperature: This uses the same DMI 2m air temperature series that has been used on some blog sites to imply no significant temperature trends in Arctic. I've shown the seasonal values as well as min/max trends and zoomed in I averaged the seasonal temp data over 80 days to phase match the “peaks” with ice extent. I also extended the ice extent data using HadISST and NSIDC ESMR data, though extent uncertainty pre 1978 and then pre 1972 is higher. The correlation of fitted second order curves is remarkable, but slightly down to chance and selection of start/stop dates, other reconstructed temp series (NCEP, ERA-40) still show high correlation, as has been noted in various papers. The summer air temp runs just above melting point, but if you average this over a few preceding months the correlation with Summer ice extent is also reasonable. In short, air temperature, SST and ice extent appear coupled together seasonally and regionally, which is kind of what you’d expect. As to why it’s warming overall… I will post links to data if I get time and people are interested.
118366. Argus at 19:52 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        #5-HR: The question after your second graph (''Why go with the one's you have choosen?'') has a possible answer as follows: If you have data from two islands, and data from one supports the point you are making, whereas data from the other seems to disprove it - then you pick the data that agrees with your theory, and discard the other. Chances are most of your readers won't bother to look for other islands. Many debaters of climate seem to reason along those principles (on both sides). Another example of selective analysis: The first graph that you showed (Ocean temperatures in the Bering Sea at M2) has an interesting comment on the page where it is originally published: the NOAA author draws the conclusion that ''Ocean temperatures for the previous decade ... show a shift toward warmer temperature of 2 deg C around 2000''. When I look at the graph, I could just as easily get the idea that ocean temperatures for the previous decade show a dramatic shift toward *colder* temperatures after 2004.
118367. Byron Smith at 19:47 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        I'm no expert, but I'd also noticed some of these issues (as outlined in the above comments). Perhaps a revision might be in order?
118368. James Wight at 18:32 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        A few points regarding muoncounter’s analysis: Firstly, some readers might not realise that ice extent is different to ice area. This is explained on the NSIDC FAQ page. Basically, area is a measurement of exactly what area of ocean is covered with ice, while extent measurements count the area of every grid cell that is 15% covered by ice. Secondly (as I see Jeff Freymueller has already pointed out), the fact that, in the graph titled “Arctic Sea Ice Change”, the two trendlines cross, does not suggest that before 1980 the minimum extent was greater than the maximum. The September trend is relative to the initial September extent, the March trend is relative to the initial March extent, and the March extent is naturally a lot higher. Thirdly, I agree with Jeff Freymueller and HumanityRules that picking one temperature series from a bunch of islands in the Bering Sea seems a bit arbitrary. However, I’m not sure that HR’s graphs are any better. Fourthly, in Figure S2 the mean is actually 1979-2000, not 1979-2009.
118369. scaddenp at 17:51 PM on 1 June 2010
        Latest 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?" No - but because business as usual scenarios will cause more warming into a system still out of equilibrium. On the other hand Gareth's little graph gives you a perspective on modern temperature compared to rest of Holocene for greenland. I certainly hope you are right about peak oil etc. but looking into past for when atmosphere was last at 450ppm, then sea level was hell of lot higher suggesting a long way to equilibrium. For questions as too how fast sealevel CAN rise from all sources, then perhaps look at Vermeer & Rahmstorf 2009.
118370. tobyjoyce at 17:39 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        Interesting clip of the experience of one researcher in the Beaufort Sea. Doctor David Barber
118371. Doug Bostrom at 17:31 PM on 1 June 2010
        Latest GRACE data on Greenland ice mass
        Wes: However, the post has been modified over the weekend. Down the memory hole! Anyway, that’s where I got the idea that someone here might possibly believe in the imminent failure of Greenland’s icecap....within our children's lifetime! Silly me. Wes, let me help you plug your memory hole. The post you refer to is this one, still plainly in sight. It's an elliptical reference to a rhetorically witty but unproductive analysis found on a website not overly concerned with useful science. As you say, silly you, heh!
118372. wes george at 17:22 PM on 1 June 2010
        Latest 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
        I also mentioned that’s strawman. But now that you bring it up: There was a post on this site that suggested if these trends not only continued on this very short slope but accelerate exponential then Greenland’s icecap will be gone in 65 years! To be fair the post mentioned that was unlikely, but still thought the possibility was worth a mention. However, the post has been modified over the weekend. Down the memory hole! Anyway, that’s where I got the idea that someone here might possibly believe in the imminent failure of Greenland’s icecap....within our children's lifetime! Silly me.
118373. Doug Bostrom at 16:41 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        HR: I've started to think that there is a regional aspect to the Arctic. What happens in the east isn't necessarily mirrored around Greenland. It seem possible to have a potitive ice anomaly in the east and negative in the west at the same time. Exactly, which is why the professionals producing measurements don't make an elementary mistake of that kind when summarizing the total ice extent. They report total extent, they don't look at a region and extrapolate from that. By way of analogy, you may move money from your checking account to your savings account and vice versa, but if you are spending more than you are saving your total available funds will diminish. It seems unlikely that one temp record in the Bering Sea is going to give insight into the whole Arctic ice extent. But of course we have Arctic ice extent to give insight into Arctic ice extent.
118374. HumanityRules at 16:32 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        Here is a longer St Paul's Island record upto 2000. From here
118375. HumanityRules at 16:27 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        muoncounter, This page (from your link) shows some quite different temperature records for the Arctic. One ocean temperature in the Bering Sea Another (St Paul's Island) which is mentioned in the text on the NOAA page. Why go with the one's you have choosen? Secondly I've started to think that there is a regional aspect to the Arctic. What happens in the east isn't necessarily mirrored around Greenland. It seem possible to have a potitive ice anomaly in the east and negative in the west at the same time. It seems unlikely that one temp record in the Bering Sea is going to give insight into the whole Arctic ice extent.
118376. Doug Bostrom at 16:27 PM on 1 June 2010
        Latest 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.
118377. Steve L at 16:26 PM on 1 June 2010
        On 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.
118378. Doug Bostrom at 16:23 PM on 1 June 2010
        On the Question of Diminishing Arctic Ice Extent
        Arctic sea ice: the Albino Canary in our global coal (and oil) mine.
118379. Sustainable2050 at 16:19 PM on 1 June 2010
        On 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.
118380. wes george at 16:12 PM on 1 June 2010
        Latest 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?
118381. Jeff Freymueller at 15:49 PM on 1 June 2010
        On 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.
118382. Doug Bostrom at 15:31 PM on 1 June 2010
        Latest 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.
118383. wes george at 15:18 PM on 1 June 2010
        Latest 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).
118384. scaddenp at 14:42 PM on 1 June 2010
        Latest 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.
118385. scaddenp at 14:26 PM on 1 June 2010
        Latest 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.
118386. Doug Bostrom at 14:04 PM on 1 June 2010
        Latest 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.
118387. wes george at 13:46 PM on 1 June 2010
        Latest 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.
        
118388. Doug Bostrom at 13:18 PM on 1 June 2010
        Latest 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.
118389. SoundOff at 12:59 PM on 1 June 2010
        Could 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. …”
118390. wes george at 12:58 PM on 1 June 2010
        Latest 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.
118391. Jim Eager at 11:36 AM on 1 June 2010
        Could 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?
118392. johnd at 10:27 AM on 1 June 2010
        Could 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.
118393. Alexandre at 09:55 AM on 1 June 2010
        Could 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...
118394. Marcus at 09:31 AM on 1 June 2010
        Could 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?
118395. Marcus at 09:28 AM on 1 June 2010
        Could 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.
118396. Alexandre at 09:18 AM on 1 June 2010
        Could 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?
118397. Marcel Bökstedt at 08:48 AM on 1 June 2010
        Websites 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.
118398. Peter Hogarth at 07:45 AM on 1 June 2010
        Why 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?
118399. scaddenp at 07:32 AM on 1 June 2010
        Empirical 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".
118400. shawnhet at 06:17 AM on 1 June 2010
        Working 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.

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