As most of you are aware, I had predicted that the 2010 minimum of arctic sea ice extent as measured by JAXA would be 4.78 million km^2. This turned out to be a remarkably close prediction, because the minimum (so far, which is probably but not certainly this year’s actual minimum) was 4.813594 million km^2. I was off by less than 1 percent.



Why was my prediction so close? There’s a very simple, and correct, answer to that: I got lucky.

My prediction was actually 4.78 +/- 0.95 million km^2. It was based on extrapolating the existing trend (a nonlinear trend) one year into the future. Since the existing trend appears to be continuing unabated, it’s no surprise that the observed figure was within my predicted range. It is a surprise that it was so close; there was only about a 1-in-40 chance that it would end up as close as it did.

Here in fact is the data on which I based my prediction and the trend line fit to that data:

The prediction itself, together with its 95% confidence interval, is the red dot on the right with error bars. It’s kind of hard to see the red dot because the black “x” marking the observed value is so close to it.

Now let’s get to the important point.

The observed value is almost dead on the value expected from extrapolating the existing trend. That means that this year’s observation not only utterly fails to contradict the existing trend, it actually supports its unabated continuation. The evidence from this year is in, and it says plainly: the existing trend continues.

In fact any value within the predicted range would lead to the same conclusion. Even if Steve Goddard’s prediction had turned out to be exactly correct and this year’s minimum had been 5.500000 million km^2, it would still be within the expected range of the existing trend. Make no mistake: this year’s data confirms the existing trend.

But if it had ended up as 5.5 million km^2, you can bet that Steve Goddard and Anthony Watts and their readers would be crowing about how it demonstrated a “recovery” of arctic sea ice extent. In fact, some of their readers have stated that the actual observed value is evidence of further recovery! How stupid can you be?

The arctic is warning us. Global warming is real. It’s caused by human activity. And it’s gonna be bad.