IPCC 2007 projections for Arctic sea-ice 2080-2100 (right image)
by David Spratt, via Climate Code Red
The Arctic sea-ice big melt of 2012 “has taken us by surprise and we must adjust our understanding of the system and we must adjust our science and we must adjust our feelings for the nature around us”, according to Kim Holmen, Norwegian Polar Institute (NPI) international director.
From Svalbard (halfway between mainland Norway and Greenland), the BBC’s David Shukman reported on 7 September that Holmen had described the current melt rate “a greater change than we could even imagine 20 years ago, even 10 years ago”.
As detailed last week, the thin crust of sea-ice which floats on the north polar sea is now only half of the average minimum summer extent of the 1980, and just one-quarter of the volume twenty years ago.
Yet the IPCC 2007 report suggested sea-ice would last all, if not most, of this century: “in some projections using SRES scenarios, Arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century”. One modelling image in the IPCC report (below)shows sea-ice still existent in period 2080-2100. This has proven to be dramatically conservative.
“As a scientist, I know that this is unprecedented in at least as much as 1,500 years. It is truly amazing – it is a huge dramatic change in the system”, says the NPI’s Dr Edmond Hansen. It is “not some short-lived phenomenon – this is an ongoing trend. You lose more and more ice and it is accelerating – you can just look at the graphs, the observations, and you can see what’s happening.”
And the trend is clear. Cambridge Professor and Arctic expert Peter Wadhams predicts Arctic summer sea ice “all gone by 2015”, except perhaps for a small multi-year remnant. Other Arctic specialists are now saying we will see an ice-free Arctic in summer within a decade or so.
Clearly the IPPC 2007 report is no longer scientifically adequate on the Arctic – and much else – and Holmen’s call to “adjust our understanding of the system and… adjust our science” is timely. The nub of the problem is that climate policy-making in Australia, and internationally, is stuck in the IPCC 2007 frame and is thereby disconnected from what is occurring on the ground, in the seas and at the poles. For that reason it can only fail.
The IPCC 2007 report dramatically underestimated sea-level rises to 2100, as being in the range of 0.18–0.59 metre this century, “excluding future rapid dynamical changes in ice flow”. Because ice sheet melting and carbon-cycle feedbacks such as permafrost are non-linear or difficult to model, the IPCC report projections “do not include uncertainties in climate-carbon cycle feedbacks nor the full effects of changes in ice sheet flow, therefore the upper values of the ranges are not to be considered upper bounds for sea level rise.” The use of paleo-climate (climate history) data as a guide to future sea levels, as advocated by researchers such as James Hansen of NASA, was excluded.
Four of six emissions IPCC scenarios found the “best estimate” of warming to 2100 to be at or below 2.8°C, whilst the trigger for substantial Greenland ice mass loss was put at at 2.7°C with a range of 1.9-4.6°C, “if global average warming were sustained for millennia” (my emphasis).
Put this IPCC 2007 picture together, and the science frame we get is: