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"I point you to this article, where Rignot clearly disagrees with Hansen's projections:" No, Rignot produced some research which produced different figures. Two projections can come up with different results and not disagree with each other. The methodology and the questions being asked were completely different so it's not surprising that a different result was reached. AFAIK Rignot's research is mainly a bottom up exercise. Taking the warming so far, analysing the geography of each ice-sheet/shelf individually and modeling what melt will happen in future. If melting is above non-linear then this will be a lower-bound. Hansen's paper takes more of a top-down approach of ice-sheet mass loss, feeds in mechanisms why this is and will continue to be exponential and produces a figure for SLR. If, for any reason mass loss is not exponential (and many people have put foward reasons why not) then this will be an upper-bound figure. Rignot says himself that it is hard to come up with an upper bound.
Bobcobb, Some general comments on your post. 1) I sometimes agree with your point on extreme predictions, although this board and forum are better than many other places. However, part of the scientific method is to make predictions and then test them against actuality. Often more is learned from the predictions which are wrong than those that are correct. So rather than switch off entirely I would suggest nudging people to make predictions that are testable (no more "torch"!), reviewing the accuracy of the prediction and then attempting to learn from the results. (And I speak here as a person who has a record of over-estimating ice melt in Neven's prediction polls ;-) ) Making incorrect predictions without scientific foundation but repeating them indefinitely is a trait of denier websites. Hopefully places like this one can rise above that. 2) Robert Scribbler is a story teller. Melting ice does not very often produce a dramatic scenario. I therefore often find his posts on arctic ice to be the weakest of his posts. So don't read 'em - it's your choice. I would however encourage you to read the comment sections because the group of posters there provide a brilliant resource of climate change related stories from around the globe. 3) On a more technical level, it is my own personal view that arctic ice melt is often over-estimated on this forum because the impact of warm, clear, high-pressure weather conditions on the ice is over-estimated. The 2012 record is unlikely to be broken until we get another GAC like 2012. The detail of this argument is most probably best in another place. The negative feedbacks on ice melt are also more than likely underestimated.
D wrote: "The Gulf Stream has not shut down. You are misinterpreting the strong thermal gradient in the mid Atlantic. The Florida current cable shows that the Gulf Stream has been strong this year. Flow across the Atlantic appears to be faster than normal this summer based on that strong gradient which is also evident in sea surface heights. Clue: More warm water than normal is moving into the Barents sea and more cold water is flowing out of the Labrador sea." Got any links or data to back this statement up? Paul Beckwith (and James Hansen) would appear to disagree with you:
Toggle Commented Aug 12, 2015 on ASI 2015 update 5: late momentum at Arctic Sea Ice
The article appears reasonable although it seems to imply a trend when the researchers have specifically warned against doing this.Much worse was the headline I heard this morning on the radio: something like "Arctic sea ice nothing to worry about. No ice loss in the last five years" - nearly choked on my cornflakes! Didn't hear any item on the story so don't know if this was put into context when discussing in depth. Worryingly the BBC seems to have taken a sharp turn into skeptical/denial territory in the last few months. Not good.
Toggle Commented Dec 15, 2014 on In the meantime: CryoSat at Arctic Sea Ice
Re: Henry1 and ChrisR It is only a single observational point, but with several years of watching the AO during summer I can back up that this year is different. In past years, when AO was strongly negative then it has been v. wet in the UK (which makes sense because you would expect lower pressures to dominate at this latitude). The correlation got to be so strong that the AO prediction could be taken as a rough weather forecast for 5-7 days in advance. This year, the AO has mainly been negative but the UK has had a lot of quiet weather with relatively high pressure so far this summer. Once again the climate/weather has thrown up something different.
Toggle Commented Jul 7, 2014 on ASI 2014 update 4: high times at Arctic Sea Ice
Hi Neven, Over on the ASIG page the pressure map for the arctic is not updating. It seems that this link is no longer valid. Can you fix it please (I would like to be able to track those great arctic storms). Unfortunately my German is not good enough to figure out where the link has moved to or whether it still exists on that site. Can anybody else help with a new link?
Toggle Commented Apr 14, 2014 on PIOMAS April 2014 at Arctic Sea Ice
Thanks Jai. I sort of guessed the answer would be something like that but then the dumb part of my brain kicks in and convinces me that it must be a zero sum situation. The positive feedbacks always seem to increase more than the negatives though. Mike: If that was a polite redirection to the 'Stupid Questions' thread you don't need to be so obtuse next time ;-)
Apologies if I interrupt the discussion about weather but I have some questions about the longer term climate implications of these results which I haven't found elsewhere. Can anybody help on these? 1) If this reduction in albedo is equivalent to 25% of global warming by CO2 (and assuming that this is not completely taken account of in the models) and taking it that atmospheric warming has roughly been predicted accurately by the models what does this new result mean for sensitivity to increased CO2? That is, if this is a component to be added in the models to those factors causing warming then there must be a corresponding reduction somewhere else? Since C02 is the major component then the likelihood is that CO2 component will reduce. Where is the flaw in this logic? 2) If this albedo reduction component is not accurately represented in the models and that the models have under-estimated the rate of arctic ice loss what does this mean for the modelled temperature increase in the 21st century? That is, if albedo reduction is under-estimated and loss of ice is also under-estimated in the models, since both of these cause warming then the predicted temperature rises in the models must also be under-estimated. If so, by how much? 3) If 1) means that C02 sensitivity is reduced but 2) means that 'natural' positive feedbacks are having more of an influence on temperature doesn't this mean that the main conclusion of the research is that humanity has less control of future temperature via reducing C02 emissions? That is, (to paraphrase Richard Alley), we can twiddle the thermostat control knob but it won't have much effect?
Hi Neven, I have several things to say about the widget. Is it OK to put them in the comments here or do you prefer discussion taken to the forum?
Toggle Commented Dec 5, 2013 on PIOMAS December 2013 at Arctic Sea Ice
Phil263, IIRC from discussion on this blog on PIOMAS from a few years back: recent sea ice area values (and maybe extent too) are an input into the PIOMAS 'model'. I do not know the details of PIOMAS but I would expect these parameters to be a large factor in the PIOMAS results. Therefore PIOMAS being consistent with sea ice area values and/or extent is not a surprise. Is there a brief summary of PIOMAS somewhere e.g. inputs, assumptions and method? It could be useful for all to learn and/or refresh on the PIOMAS model.
Toggle Commented Aug 4, 2013 on PIOMAS August 2013 at Arctic Sea Ice
3.3 +-0.6M Km2 Up from 3.1 previously. 100% intuition. To be honest think that the value could be anywhere in the range provided. There is at least 1M km2 of flat, bad quality thin ice. Whether this melts or not depends on factors which cannot be predicted or even measured. That is, the metric of minimum sea ice extent is now chaotic. Is that open water on the right side? Looks like we have a beach-side view now. This says something about the state at the pole. Sun is out as well...
3.1 (same as last month) Hunch rather than any mathematical process. Expecting 'dead cat bounce' because of change of state of ice. expecting type of weather to make little difference - therefore to be consistent have to stay with original number even if this summer is going to have cool weather. I don't believe the start to melting has been that slow - it's just the numbers used to measure ice melt aren't showing it (yet) e.g. PIOMAS is a model - if the ice state is a new state then how can it model it accurately? However there is less confidence in the guesstimate than last month. It seems the melt is on a knife edge. We could be seeing some new (unexpected) negative feedbacks coming in due to the new state of the ice.
3.1 million km2 history would suggest a rebound after last years significant decrease. However (unlike previously) the majority of last years decrease was not caused by extreme weather. Arctic cyclones could now be the norm. This suggests a paradigm shift has occurred in the cryosphere. positive feedback of reduced albedo, increased inflow of warmer water, reduced snow cover, less multi-year ice etc. suggests there will only be decreases until zero is reached.
Werther, Whitebeard: I suggest not proceeding down that route with the antarctic data. That can lead to the two sides just talking numbers to each other - the majority (who we are trying to persuade) can get fed up with both sides and lose interest. It will be better to focus on why the antarctic figure is not matching the arctic melt even though the antartic is warming. AGW will impact different regions in different (often unpredictable) ways at different times - this is a key message. actually in this case the mechanism seems to be quite straightforward and is understood. in other scenarios it may not be. Also what do you say in the future if antarctic increase is greater than arctic decrease? This is theoretically possible because the annual arctic decrease is bounded (and getting more bounded all the time) and the antarctic increase is in the short term unbounded.
Toggle Commented Sep 21, 2012 on (not so) Cool vids at Arctic Sea Ice
@Karl, I suggest you look at the skeptical science website, especially the following links rebutting specific points you have made. If you have any questions on these points please post them on the correct thread on skeptical science. "natural cycles powered by solar cycles" "only causing warming at certain times and in certain places" "look at a trace gas"
and for webcam watchers, surf's up at Barrow (again). Also there seems to be a lot of standing water, and they seem to be building additional sea defences...
Toggle Commented Sep 17, 2012 on Minimum open thread at Arctic Sea Ice
imho, when the history of AGW comes to be written one of the major mistakes noted will be the over reliance and too much emphasis being put on computer models. Too inaccurate and too easy to attack by skeptics. Hansen and Alley seem to have realised this and now only focus on the paleoclimate record - after all the earth is the best model for the earth. IIRC antarctic ice sheet started to appear when C02 dropped below 450ppm. From current observations, summer arctic ice disappears at approx. 390-400ppm. GIS presumably disappears somewhere between these two: 400 and 450ppm. Do we need to know anymore than these three numbers?
Hi Lodger, Roman: I think what Roman means is 1st Sept image - here (sorry if link is wrong - first time embedding a link on this site). If you go straight to Webcams it never shows latest image (don't know why) - you have to go to archive to see those. On left hand side is open water - that is not a melt pond imho.
@oldleatherneck & neven: Additional to people thinking AGW will only impact in the future is people thinking that the impact will be a single step change. I think this is partly due to the wording of some AGW projections e.g. the sea level change projections: "sea level will be x metres higher in 100 years time". This immediately makes you think that some time between now and then sea levels will rise x metres almost overnight in a single step. Although a hardship all people living in affected areas will have to do is move to higher ground and rebuild cities & infrastructure at the higher point and that will be it. Must admit I got to thinking this way for a while. Of course the killer is that the changes will be either continuous change or worse with erratic bursts of increase and then periods of no increase. In this scenario how do you plan and build new ports, oil terminals, sea defences etc.? There must be some way to build all these with robustness to SLR change built in - I suspect this makes them much, much more expensive. This is one area where Bjorn Lomberg et al. miss most of the implications and therefore miss most of the costs (both human and economic)
Toggle Commented Aug 23, 2012 on Peeking through the clouds 5 at Arctic Sea Ice
Hi Rob, Also struck me this morning how the ice is centred on the NP stretching out to on average of 80 degrees south. One explanation is that the way in which the ice melts has changed: Instead of a solid ice-pack which melts in-situ it is now a slush puppy which gets moved about by wind and water. Melting IS happening North of Svalbard it's just that the ice is being constantly replenished. If you like north of svalbard is the new Fram Strait. Next year it may be cold over svalbard and warm over the other side. Likely that in late summer the ice will again be centred over the NP. What's wrong with the above is if the ice was a slush puppy I would expect the buoys to move more than they have.It looks like buoys 4 and 6 are hardly moving...
Hehe good mis-type: "arctic CO2 sink" mime. The mime artist slowly pulls out an empty pocket on the left. No CO2 sink there. Then they slowly pull out an empty pocket on the right - no CO2 sink there. Then they look straight at the audience with a very sad stare and shrug their shoulders showing both empty hands. Nope - no CO2 anywhere.
Toggle Commented Aug 11, 2012 on Arctic summer storm open thread 1 at Arctic Sea Ice
While we are waiting to see what happens with the storm, it seems to be a good time to ask this (most probably stupid) question which has bugged me for some time which I can't find the answer to. Assuming an ice-free arctic ocean in the future what will the track of Arctic lows be? The simple model I have in my head says that the track of an LP mainly depends on three factors: 1) Heat energy. The low needs energy (mainly from surface water) to continue to keep itself alive. This means the lowest pressure tends towards areas of highest energy (warmest water) 2) High-level winds can drag the top of the LP and the lower (in height) parts of the LP follow: I always picture a tornado leaning over with the top leading the surface part of the funnel. Scale this up and a similar process happens in an LP. By high level winds I mean the global circulations e.g. jet stream 3) rotation of the earth. Don't know exactly the impact of this but I would have thought this must have an effect either via Coriolis effect or indirectly via (2) Taking all of the above at the north pole 2) and 3) will be roughly zero. Does this mean that if enough energy is provided an LP could be located at the north pole indefinitely and never move? PS: Great blog Neven. I have watched and learned for 3 years. Now seems the time to come out of the shadows.
Ah yes, thanks - didn't know those pictures existed.
anthropocene is now following Neven
Aug 7, 2012