There isn't all that much fake skeptic nonsense going round when it comes to Arctic sea ice. Climate risk deniers rather just ignore the geologic time scale event going on up North that could lead to an ice-free Arctic Ocean within one human lifetime. Still, every now and then an effort is made to trivialize Arctic sea ice loss. In this case it is done by averaging all daily sea ice extent numbers over the course of a year, and then claiming that Arctic sea ice is recovering.
The source of the claim is this graph based on MASIE data, which is the subject of this blog post. I'll get to that later, but here's the 'recovery' graph:
I'm not even going to link to the blog in question, because it's full of misleading and embarrassing statements by an older gentleman whose mind has obviously been set in concrete a while ago, and this particular nonsense has been taken apart by Tamino back in September. Of course this hasn't discouraged the blogger in question to stop misleading his readers, and his latest production of the useless annual average nonsense* has, again, been taken up by the free market fundamentalist ex-banker hobby organization known as the (no) Global Warming Policy Foundation.
All of this wasn't all that interesting to me until I compared the 'recovery' graph with an annual average graph based on JAXA sea ice extent data (found here):Here the trend line goes down instead of up, 2012 is lower than 2007, and 2015 has the 4th lowest annual average instead of 6th. That's quite a difference. What could be causing it?
Now, the MASIE FAQ page has this:
Use the Sea Ice Index when comparing trends in sea ice over time or when consistency is important. Even then, the monthly, not the daily, Sea Ice Index views should be used to look at trends in sea ice. (...) Use MASIE when you want the most accurate view possible of Arctic-wide ice on a given day or through the week.
In other words, don't use MASIE if you want to compare trends over time and be consistent.
The Sea Ice Index is basically NSIDC sea ice extent data that is used for the daily and monthly graphs shown on the NSIDC website and can be found here (the blogger calls it a NOAA product, which is confusing, and shows how intimately acquainted he is with Arctic sea ice data). Here's what daily NSIDC sea ice extent data shows when averaged for the year:
Again, trend is down, 2012 is lowest, and 2015 is 4th lowest. How about Cryosphere Today sea ice area data (found here)?
To top it off, here's the only freely available daily data left (as far as I know) that also tells us something about sea ice thickness. It's PIOMAS sea ice volume data (found here), which is modeled data, constrained by observational data that is assimilated into the model:
Trend line very much downwards, 2012 lowest, but 2015 is 6th lowest here too (after the 2013 and 2014 rebound years there was more ice during the first few months of the year). Mind you, this data runs up to November 30th, because the PSC hasn't released December data yet.
So, no data set agrees with MASIE. Here's another quote from the MASIE documentation page:
While operational analyses [like MASIE; N.] are usually the most accurate and timely representation of sea ice, they have errors and biases that change over time. If one is interested in long-term trends in sea ice or how it responds to changing climate forcing, generally, it is best not to use an operational product, but rather one that is consistently produced and retroactively quality controlled.
Does this explain the differences between MASIE and all other available daily data sets out there? Or are there other reasons as well? I can't imagine that just because of the human component in MASIE data construction (analysts trained in remote sensing imagery interpretation and sea ice climatology) an interannual comparison can be so different from those of other more consistent data sets.
Either way, even if an annual average graph wouldn't be a very poor and silly basis for claiming recovery, you still shouldn't be using MASIE data to do so. That the GWPF amplifies this misinformation by spreading it, is wrong and reprehensible. Remember who lied to you.
* Why is it useless? That's simple. It doesn't tell us all that much about the health of Arctic sea ice. It's like measuring your weight every day from Jan 1st to Dec 31st. You're really overweight at the start year, then you stop eating for half a year and you get really thin and undernourished, followed by a junkfood binge after which you're overweight again. But then you take the average of all those daily weighings, and presto, your average weight is perfect! But, one might ask, how's your health?
What an annual average is basically showing us, is that winter still exists, and that when a lot of sea ice is lost over the course of a melting season, the regrowth curve of ice will also be spectacularly steep. But it tells us nothing about the maximum, and more importantly the minimum and the period preceding it when there's lots of open water absorbing solar radiation, further heating up the Arctic. The other problems with this kind of data misrepresentation, is that 10 years (MASIE data collection started in 2006) is too short a time frame for meaningful trend lines, and that sea ice extent is a two-dimensional measurement that doesn't tell us anything about sea ice thickness or volume.