Eli Heads North

One of the things a smart bunny learns is that if you see something new to you in an area you really don't follow, everybunny else who follows the dots has seen it, but you have not seen them seeing it.  Yet, since on rare occasion they have not seen it because it is so obvious it is worth asking about and one might even learn something

Worse, in Eli's case, this is something that finally percolated through because of nonsense that Andrew Montford at Bishop Hill wrote trying to handwave the weird ice coverage this winter up north (yes, Eli knows everybunny and his brother in law is racing south to watch the Antarctic ice shelves collapse, but this is Rabett Run, Eli and Brian follow their own pipers).  Montford opined

As usual on these occasions, I take a quick look at the Cryosphere Today anomaly page, where I find the sea ice apparently still stuck firmly in "pause" mode.

As fate would have it Eli had been looking at this chart for many a year, and there, as discussed below, were things about it that well stood out to anybunny who spent their life looking at charts, things that were. . .and are . . . maybe. . . .interesting.

For example, it is clear that the nature of the anomalies changed somewhere around 2006.  The pattern of the anomaly between 2007 and 2016 is very different to that previously.  With a thirty day smooth, the post 2007 pattern is hard to miss

There is a clear minimum in September, not very exciting.  One can see this in 2013 and 2014, although not as clearly in the other years, but it is there.  However, there are also secondary minima in May/June in all of these years. 

Equally interesting is the period 1996-2006

Rather than the winter/summer pattern seen in the 2007-2016 period in the anomaly there is a roll off in all seasons, about the same loss of sea ice year round (e.g. the decrease each month was about the same or at least the month to month variation was smaller.  But what about before 1996

Eli will not engage in cycling.  HIt is true that because anomalies compare like with like, e.g. the ice area in the same month against some reference period (1979-2008 in the examples above) looking  just at anomalies can be tricky.  The boys from Bremen have a useful comparison of September minimum extent between 2012 and 1979-83

and if one looks at the period between 1979 and 2015 on the maps at Cryosphere Today the changing pattern in the September ice area is obvious. 

Oh yeah, Cryosphere Today has a useful reminder of the ability of an anomaly to hide the decline

c

There has been a pretty steady decline in arctic sea ice since ~ 1955.