For some data to work with further, I pulled the NSIDC September figures. It's a small, simple text file, so you can check yourself what follows. First up, let's draw a figure of what we're looking at -- but don't connect the observation dots. Our eyes tend to be led to conclusions by the superposed lines.
ice before 1979 and see that figures below 5.5 million km^2 are unprecedented in the longer records as well. To have data precision and consistency, though, I'll stay with the 1979-present.
What else can we say from eyeballing the data? Since the 1979 starting point:
- There have been 2 record highs (1980 and 1996)
- There have been 8 record lows (1984, 1985, 1990, 1995, 2002, 2005, 2007, 2012)
- There have been more record lows in the last 10 years (3) than record highs in the full 35 year record
- 1996 is about the last year one could say there was no trend in the data
- Versus eyeball curve fitting, 1996 is the most exceptionally high year (not just an absolute record, but even higher above smooth curves we'd try to fit to the data than any other year).
- More recent years look like they have more scatter than the earlier years
- It looks like we might want to divide the period in to 3 intervals -- 1979-1996 (the longest arguably trendless span), 1997-2006 (an intermediate with at least some overlap on the earlier figures) and 2007-present (entirely outside the range of the previous years)