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Michael Stefan
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If you actually read the fine details, this study, if correct, is actually very BAD news for the future. Why? It assumes that the temperature change since the last Ice Age was actually much lower than currently assumed and as a result the climate is FAR more sensitive to temperature changes than thought. Joe Romm has a full writeup at Climate Progress: Note also all of the record extreme weather events over the past few years - the effects from warmer temperatures alone are comparatively so insignificant that I wish people would stop focusing on how much warmer it will get, when floods, droughts and storms have a much bigger impact.
L. Hamilton, as you referred to UB rising for a couple days, I believe that the rise it shows isn't real because when I looked at the map the other day I noticed anomalous areas of ice where there obviously wasn't any, especially a quite large area in the Sea of Okhotsk. CT also shows anomalous ice in Hudson Bay on the current map (9/2). Presumably, this is what is referred to when satellite error is mentioned; I wonder why they can't perform a "sanity check" to reduce errors (e.g. there should obviously be no ice in the Sea of Okhotsk right now).
Jacobson says his calculations show controlling soot could reduce warming above parts of the Arctic Circle by almost 3 degrees Fahrenheit within 15 years, virtually erasing all of the warming that has occurred in the region during the last 100 years I read that as saying that GHGs have had NO warming effect whatsoever, which strikes me as very shortsighted, focusing on just one factor. Plus, why did the Arctic cool in the 1940s-50s when increased aerosols caused global temperatures to stagnate (generally following NH temperatures, note that SH temperatures didn't cool or stagnate, and the Arctic is rapidly warming over the past decade when mid-lat NH temperatures have stagnated, unlike the first time)? Sea ice also doesn't last long (especially now) so I'd think that soot wouldn't be able to build up much (except for Greenland); in fact, new ice that forms next winter will have had only months at the most to accumulate soot.
Paul: ...For Arctic ice melt, every data point in the summer is not only 1 sigma out, but 2 sigma out, and some seem to be 3 sigma out... The NSIDC graph shows that it is even more extreme than that; the shaded area is +/- 2 sigma and the current extent is about 2 1/2 times further away from the average than the 2 sigma band, making it closer to 5 sigma below average, which is supposed to be a 1 in 1744278 probability event (I know that you can't really use that probability value but it shows how anomalously low the ice is right now).
Somewhat OT, but according to total NH snow cover (including land, sea ice, and Greenland) has set a new daily record low, surpassing the previous record set last year and prior to that, 2007; about 25% below the 1995-2009 average. Also, statements to the effect of "GHGs account for 10% of current ice melt" ignore the fact that GHGs started the warming in the first place (ignoring natural variability, which has no significant trend and was on a long-term cooling trend until recently), even if feedbacks are becoming more significant, such as increased SSTs in ice-free areas.
Toggle Commented Aug 31, 2011 on SIE 2011 update 18: ten yard line at Arctic Sea Ice
Paul, it still doesn't make sense that IJIS would label 10 day old data as being from yesterday. Also, the 2007 minimum was 4.25 from IJIS and 4.13 from NSIDC. True, it occurred 8 days later according to IJIS, but it is hard to believe that delayed data being passed off as more recent was the cause. On the other hand, the minimum last year occurred within one day in both datasets (ignoring the 5 vs 2 day averaging), but was 200,000 km3 higher for IJIS, similar to what you observe for the present.
Toggle Commented Aug 28, 2011 on SIE 2011 update 18: ten yard line at Arctic Sea Ice
The recent comments about week old (or more) data don't make sense to me - why would they label data from August 16th as being from the 26th? Not only that, just eyeballing the graphs suggests that, at the most, they can't be more than a day or two behind the current day (or they would stop near mid-August), and IJIS shows the most recent day with data as the 26th in their data file. It is more likely that the differences lie in the different sensors and algorithms used; NSIDC recently made a remark about Bremen data showing more open water due to higher resolution.
Toggle Commented Aug 27, 2011 on SIE 2011 update 18: ten yard line at Arctic Sea Ice
It seems to me that the Southern Hemisphere is seeing something similar to last winter in the NH, with extreme warmth over the Antarctic and cold outbreaks in the mid-latitudes (check out South America). Not only that, the Antarctic Oscillation has been a bit screwy recently, even going off the graph (the scale for the AO was extended after the winter before last): The general pattern over both poles has been similar in recent weeks, as indicated by heights and SLP (the latter averaging as high as 1070(!) mb over the past 30 days in parts of Antarctica), only in the Arctic temperatures are being held down by the freezing point of water:
Toggle Commented Aug 23, 2011 on Flash melting at Arctic Sea Ice
If the average ice thickness over the entire Arctic was only 0.9 meters, then that means that ice volume would be only 2,900 km3, based on current CT ice area of 3.23 million km2. At that rate of decline, it would reach zero in a few more years...
Toggle Commented Aug 22, 2011 on Polarstern reaches North Pole at Arctic Sea Ice
Reasonablemadness: So, if we pass a tipping point in the arctic, warming intensifies and it will be much harder, to go back to previous temperatures. You would need stronger cooling forces as if there would be no tipping point. And IMO this is exactly what you would expect by the ice-albedo feedback. That is the way I have always seen it as; the notion of an irreversible tipping point is clearly absurd or the planet would be ice free right now (e.g. once it became ice free, it would always remain so). In any event, once the Arctic becomes ice free in the summer, it will likely require a much cooler climate than today to restore the ice. Also, while it is true that the ocean circulation/geography 45 million years ago doesn't have much bearing on today, paleoclimate is still useful in assessing the climate response to forcings (e.g. a recent study that found that the climate is twice as sensitive to CO2 as models show, never mind 16°C warmer at CO2 levels projected for 2100, or that the Arctic was ~19°C warmer than today a few million years ago with slightly higher CO2 and similar ocean circulation/geography). Note also that the Sun was dimmer in the past (much more so than over a solar cycle), which is also a big factor in comparing past to present climates.
Toggle Commented Aug 19, 2011 on Polar ice caps can recover at Arctic Sea Ice
Hi Rich and Mike and Neapolitan (Jim), It seems to me that the past few years could be one of those cases (as modeled) where ice extent doesn't decrease much, but it certainly has decreased in area and volume, due to "unfavorable" (in the sense that extent doesn't decline with the other measurments) weather patterns spreading the ice out. Also, wintertime snow cover has increased recently, but it has also melted faster in the spring, as mentioned by the NSIDC a while back in their mid-July update (recall that albedo has a much bigger effect in the summer. Also, the snow cover anomaly for June, when insolation is highest, was over 4.5 million km2, over twice the sea ice anomaly).
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Aug 11, 2011