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Is it of any particular interest that 2015 and 2016 are so far apart? (Graph 1)

Further, is it of any particular worth to ask why that may be?

Olivier Del Rio

Neven, great blog ;) I must said I'm not really optimistic for April, and even less for this summer. Contrary to others recent years, there is a memory of the huge anomalies of this winter. Usually, there is a kind of partial "reset" during April. For sea ice extent in particular, the decrease over the decades is the lowest in April - May and all years tend to converge a bit. And with heavier snowfalls during winter (more humidity with warming and so on), snow cover in late winter is not really low for recent years. Usually, snow melt in late spring -ie. May and June- is a good indicator of sea ice melt (for example 2010 and 2012...). But in 2016 this usual partial "reset" is barely noticeable. Snow cover is already very low (March was more or a less a tied record with 1990 -37.16 millions of km² in 2016 vs 37.12 millions of km² in 1990-) and the sum of all the Northern Hemisphere “white”, sum of sea ice extent and snow cover, is the lowest in record for February and March. And this trend continue in early April with low snow cover and warm about everywhere. NH is already accumulating heat. Anomalies can go back and forth and there is not so much persistence in anomalies, but there is in 2016 some kind of threshold. One thing for example, models are announcing the end of the -20°C for mid April.... According to the reanalysis, the prior for this metric was 1980 in the first days of May. If models confirms, we will cross this threshold a full 2 weeks before any prior. And again, in recent years the -20°C was not always lost early due to this kind of reset: http://imageshack.com/a/img921/7771/fAywEM.png . Reanalysis has a coarse resolution so in models with a finer resolution it can be a bit later but the idea is here (but one advantage of coarse resolution: spurious readings over Greenland are de facto eliminated. Sometimes models show cold 850 hPa temperatures over Greenland because of the high ground, but for reanalysis it is not the case). This example represents a net loss of cold if I may said. Sea ice will probably still bounce back a bit like about every April and May, but not so much and after, go to the basement. Perhaps not a new record (even with a really bad start, beating 2012 will still be tough). But chance for an increase of volume in 2016 are slim at best, chance for blowing away precedent record for sea ice extent and snow cover in April – May are high (for snow cover in particular, it's virtually certain record will be at least beaten), and we will never fully erase all the heat already accumulated in the great north. And in the same times subtropics also have accumulated heat, and I don't think we can get rid of this heat -even if anomalies can go back and forth, here we have also cross early some kind of thresholds-. For this another example, from India to Africa temperatures at 850 hPa are already above 30°C and each flow from the south let this warmth to spill (for Europe, Bosnia reach 30°C at 2 meters this days. It's one of the earliest 30°C reading at surface in Europe -compared to some 30°C en Andalucía in 2015...-). More exactly, what I mean is that we have already to much advance over seasonal cycle. For many metrics in many places, we are already at reading more typical of May. All this warmth will not be erased, it's like hoping there will be no seasonal cycle. Some early crossing of remarkble values was possible (30° en Granada en Marzo de 2015 !) but never at this scale for NH. The end of the -20°C in mid April is from this point of view the thing wich strike me the most.

Jim Hunt

Perhaps I might take the opportunity to point out that in certain parts of the cryospheric blogosphere there are those seeking to pull the PIOMAS wool over the eyes of their faithful flocks using "Andrew [Montford]'s anomalous trick" to "Hide the decline" in Arctic sea ice:

More Of The Usual Hype About Arctic Sea Ice

I find that a healthy dose of Wipneus, Reynolds and Robinson helps clear up matters, for those desirous of a cure for their blindness at least.

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