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"In other words, it has become more difficult to predict end-of-melt-season outcomes"
This is not a conclusion that can be drawn from the data shown here. To see why, consider the this data set: (10, 11), (11, 10), (10, 10) and (11,11). There is no correlation. And this dataset has no correlation either: (0, 1), (1, 0), (0, 0) and (1,1). Now, if you add these datasets together, suddenly there is a good correlation: a high number on the first datapoint always goes together with a high number on the second, and a low number with another low number.
This is exactly what happened in the arctic. In the 80s, there was high spring extent and high summer extent. In the '07-'12 period, there was much lower spring extent and summer extent. Apart, there is no correlation (natural variability overcomes the trend). Taken together, there is a correlation (the trend overcomes natural variability).
This phenomenon occurs in every dataset with a trend and random peturbations, so in itself this tells nothing about the predictability of the end-of-melt-season outcomes. A better way to test that hypothesis is to try to 'predict' each year by using the data of the other years, and see if there's a trend in the quality of the predictions. If people are interested, I can do that kind of analysis, but I suspect that any trend found is not significant. There's not enough data.
Problematic predictions
This is a guest blog by Bill Fothergill, also known as billthefrog. He sent it to me a couple of weeks ago, but it's still topical. ----- Problematic Predictions Many of the contributors to the Arctic Sea Ice Blog have passed comment on the dangers of basing an end-of-melt-season prediction on ...
In the category weather wiplash:
http://www.youtube.com/watch?v=0m_3ggLbyLQ
From frost to 100 Degrees in 58 Hours...
Climate, Ice and Weather Whiplash
Here's yet another new and great video by Peter Sinclair from the ClimateCrocks blog for the Yale Forum on Climate Change and the Media: It bears repeating... This video should get at least 50 million views. I think it will one day.
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Sep 23, 2012
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