Over six years ago (omg) I wrote about the percentage loss of Arctic sea ice, by volume, and came up with a nice little formula to calculate it under the assumption of a linear trend.
It was, then, -39.0% gone since Jan 1979.
Now it's just over six years later, and I just wanted to note that, as of Sept 2018, the figure is now -47.3%. Arctic sea ice is disappearing at over 1% per year.
Using the linear trend of -306 km3/yr, the sea ice volume loss since Jan 1979 is now -12.2 Kkm3, or -10.6 trillion tonnes.
Using a quadratic fit (easily better, in the least-squares sense), the loss is accelerating at -11.2 km3/yr2.
By the way, this acceleration is down from a (negative) peak of -22.2 km3/yr2 in Nov 2012. Sea ice loss is stalling a bit. It's done this before, and is no big deal -- there is no scientific reason to expect it will continue forever.