Over at Tamino's there is an interesting analysis of sea levels - since we discussed it at some length here it is worth a visit to read. http://tamino.wordpress.com/2012/09/26/unnatural-hazards/#more-5663

I haven't read Hansen & Sato, but Joe Romm's site gave this quote: "BAU scenarios result in global warming of the order of 3-6°C. It is this scenario for which we assert that multi-meter sea level rise on the century time scale are not only possible, but almost dead certain. " and "What about the intermediate scenario, EU2C? We have presented evidence in this paper that prior interglacial periods were less than 1°C warmer than the Holocene maximum. If we are correct in that conclusion, the EU2C scenario implies a sea level rise of many meters. It is difficult to predict a time scale for the sea level rise, but it would be dangerous and foolish to take such a global warming scenario as a goal." Yes, you are correct, Tony. I would interpret that to mean EU2C to be at least 3 meters for an undetermined time, and BAU to mean 2 or more meters by 2112. In terms of planning for infrastructure, it leave a pretty wide range between Hansen and the IPCC AR4 range of .18-.59 meters by 2099, depending on scenario - and not a lot of time to prepare if it is closer to Hansen than IPCC AR4.

Djprice537: The estimate of the percent of the worlds population to be relocated with a 10 meter sea level increase is from Deborah Balk, the acting associate director of the Institute for Demographic Research, in a study they did in 2007. I do know something about infrastructure, I'm a Professional Civil Engineer with 35 years of practice involving infrastructure design and relocation. The task of relocating 5-10% of the worlds' population would be immense, and 80 to 100 years for planning and implementation is an incredibly short time period for something of this magnitude. Believe me, I do not underestimate the task. The issue with models I was alluding to was that the probability of a sea level increase of x meters by a certain date is necessary information. When we design a dam or a levee, we look at the risk associated with failure given a set of probabilities. On a minor dam where the risk of death or damage is small downstream, we might design for a 0.5% annual probability of failure. A larger dam, where there is higher risk downstream, would be designed to a much lower probability of failure. The hydrologic and hydraulic modeling provides the basis for the design. I see the climate, and especially sea level, models as serving the same purpose. If the risk of a 10 meter increase is extremely small, we do not have, nor should we, allocate resources to plan and implement a process to accommodate that. If the risk of a 2 meter increase is high over the next 90 years, we must devote the resources for that possibility. I know that climate models are much more complex than the well established H & H models, but great effort needs to be made to improve and verify the models to avoid either wasting a limited amount of resources, or worse, failing to provide those resources when needed.

Thanks Al, With Hansen predicting up to 5m, and recognizing the arctic ice melt models appear overly conservative, it's a subject I'll need to look at closer. Adaption to 2m will be expensive, but nothing like 5m.

The relocation of 10% of the worlds population is an unimaginable task, and I don't know how it would be possible to allocate the resources to accomplish that task. What we see in the Arctic indicates to me that it is possible, though it still seems unlikely, for Greenland and WAIS to contribute sufficient melt to see a 5-10 meter sea level increase within the century. I think the modeling is of critical importance to see if climate change can (will?) impact Greenland and WAIS that amount. If the models start to provide evidence of a chance of a 10 meter increase in sea level, then the Herculean task of planning for the relocating 5-10% of the worlds population and the infrastructure to service them would need to be done. Not to mention the changes to the water and food supply chain that would have to occur concurrently. It makes a real difference relocating, say, 2% of the worlds people verses 10%.

Andre: The number of humans living within 10 meters of sea level seems to be in the range of 600+ million. http://sedac.ciesin.columbia.edu/gpw/docs/McGranahan2007.pdf

The same Polar bear seems to have visited Obuoy #4, leaving tracks and may be leaning against the camera, giving a bit of tilt.

Today, Modis has a very good image of the ice in Nares Strait coming apart: http://lance-modis.eosdis.nasa.gov/cgi-bin/imagery/single.cgi?image=crefl1_143.A2012184012500-2012184013000.250m.jpg

While sunning myself on the unusually ice free shores of Lake Michigan, it feels like spring is imminent. But I think we've got another 30 days for increased area and am guessing at 3.15 million km2. That would put it at day 61-63. A virtual tie with last year.

I know I've received far more value from Neven and the other contributors to this blog than the small amount I was able to donate. Thank you all. I believe the distribution as shown above is very fair. The Darfur Stoves Project certainly seems worthy. Yazzur

Ah, they've been revised now.

Something seems to be wrong with the Cryosphere Today numbers for 9 May 2011. Hudson Bay, Arctic Basin, and the Canadian Archipelago ice extents are showing significant drops.

Nice job Neven, I see the poll in the right column in Firefox. Yazzur

Based on physical observations, I would be very surprised if area and thickness were a linear relationship. On the Great Lakes, it's not unusual to see a large area of ice disappear in the matter of a few days. It's often a quick ice out, Lake Erie can essentially lose the ice cover in a week. From observing ice out on smaller lakes, it more often is such that the ice continues to thin over a whole lake until winds break it up in a day. Although the seas are not the Great Lakes, it would seem it would be similar, with the ice thinning over large areas until such point it was thin enough for a weather occurrence to break up a relatively large area in a very short period of time.

Interesting paper by Hansen & Sato, here: http://www.columbia.edu/~jeh1/mailings/2011/20110118_MilankovicPaper.pdf Makes some of us here seem like optimists. Yazzur

Nice summary Yooper, I was in the Keweenaw for 5 years, so I'm still bit of a Yooper. Although not arctic ice, for those interested, here are ice maps for the Great Lakes: http://www.glerl.noaa.gov/res/glcfs/glcfs.php?lake=l&ext=ice&type=N&hr=00 Even with warmer than normal water in the Great Lakes, our lake effect snowfall not as much as usual. Lake Michigan water level is 19" below the January average, 9" above record lows, and 53" below record high. Yazzur

"Daniel, I'm guessing from the tag that you're from "Yooper" Michigan?What news from the Great Lakes this winter? Ice free yet?" I'm a troll (Michigan definition - living "under", or south the Mackinac bridge,), on the little finger of Michigan, and so far, Lake Michigan is ice free, but that is not really unusual for this time of year. There has been a gradual reduction in freeze over on the larger bays over the past 20 years, with my local Grand Traverse Bay not freezing several times in the past 10 years, historically it's unusual for it to not freeze. Who's the Hudson Bay expert here? Has it ever not frozen over? Yazzur

Is anybody watching the far northeastern corner of Greenland (near Kap Bridgman?), and the large ice chunks breaking off? I thought this area was mostly multi-year ice. It looks like several large cracks are starting to open up in that area.