Update: The NSIDC dataset has a column called “Missing”. It never has any data in it. Until now.
In the Arctic the only data with data in the Missing column:
| Year | Month | Day | Extent | Missing |
| 2013 | 11 | 9 | 9.27397 | 0.00049 |
| 2013 | 11 | 10 | 7.1533 | 5.13051 |
Antarctic
| Year | Month | Day | Extent | Missing |
| 2013 | 1 | 14 | 5.58306 | 0.00109 |
| 2013 | 11 | 9 | 17.73409 | 0.01129 |
| 2013 | 11 | 10 | 11.16475 | 16.20944 |
Actual data from NSIDC. I think they missed some ….
sunshine hours 
Either that data link took a crap, or they are adjusting their data and didn’t think we would notice. Ha!
They have a disclaimer on their website: “November 6, 2013: Data updates are currently intermittent due to technical difficulties with the data provider.” http://nsidc.org/data/seaice_index/index.html