With all the wild excitement over 2007’s record low there is clearly room for noise to be made about summer sea ice, so predictions must be made! We all know, of course, that whether this year, or any other year, is going to be a record is going to be a matter of chance: on top of the long term negative trend (and we can argue about whether that trend is typified by the slope of 1979-2006, or has got steeper recently) there is a lot of interannual variation. Certainly I’m not aware of any sea ice modeller with enough confidence in their predictions to put any money on them.
But the next best thing is a press release, such as New record Arctic sea ice cover minimum? Climate researchers from Bremerhaven and Hamburg present new prognoses. from AWI. Now the heading is clear enough: they are interested in the question of a new minimum. What is objectionable is the next bit: The German researchers agree upon a continuing negative trend. Another critical minimum of Arctic sea ice is to be expected in the late summer of 2009.
Well, there you go: a clear prediction of a new minimum this summer. No? Well, no. Because the text then gets a bit smaller and says: We have computed in this year’s first prognosis that the ice cover of the Arctic Ocean will lie at the end of the summer with at least 28 % probability under that of 2007 – the year with the lowest-ever measured ice extension. Put simply, “is to be expected in the late summer of 2009″ is wrong. It should be “has an approximately 1-in-4 chance in the late summer of 2009″, based on their model. Or you could read a bit further on and find that Hamburg say: We estimate a probability of 7 % that this year will fall below the negative record of 2007.