As I mentioned yesterday, NSIDC had an oops moment, but with the help of skeptical blogs, was notified of the problem and responded timely and appropriately. They posted this update today:
Update, April 19, 2012: The nine-day trailing average climatology on the daily data graph has been changed to a five-day trailing average, to be consistent with the five-day trailing average for the daily data.
I verified their correction for the climatology was accurate with a new overlay, combining the unaffected graph NSIDC’s Dr. Julienne Stroeve sent me from their internal server storage Tuesday night with the corrected one published on the web today:
The extent data and the climatology now match, whereas yesterday they did not. The x-axis offset is to be expected given that we are comparing graphs with the temporal data offset due to a trailing average they implemented.
This is what the same comparison looked like yesterday, for graphs made on the same day:
So, problem solved.
Unfortunately, somebody jumped to a conclusion and has already had to issue a correction.
The maxim “haste makes waste” seems appropriate.
The way NSIDC’s Dr. Walt Meier and Dr. Julienne Stroeve handled this should be an example to other agencies that don’t bother to even respond to skeptics.