A few weeks ago, I caught NSIDC pulling some mathematical nonsense in their sea ice graphs. A few hours before the Arctic extent line was about to cross the mean line, they changed their plotting scheme to use a five day trailing average for the current ice and a nine day trailing average for the climatology. I pointed out to them that they can’t do that because it puts a two day relative shift in the data – and they fixed it the next day.
Amazingly, they have made a new mistake in their latest Sea Ice News. The graph below shows all recent years far below climatology.
Compare vs. their current extent graph, which shows the blue line brushing up against the gray line last week.
I overlaid the current graph on the Sea Ice News graph, and you can see the error in their climatology (thick grey line.)
I don’t think this is the same error as they made two weeks ago, because the climatology line doesn’t line up using a horizontal shift.
h/t to Rogelio