This year’s story so far: in May, I accepted some bets but was still trying to come to terms with Rob Dekker. In the comments there we came to agreement on the following:
If both NSIDC and IARC-JAXA September 2016 monthly average sea ice extent report are above 4.80 million km^2, RD pays WMC US$ 10,000. If both are below 3.10 million km^2, WMC pays RD US$ 10,000. In all other cases the bet is null and void
The numbers are a bit of a compromise, and of course the large “null gap” in the middle means a no-payment result is quite likely. Now is a sort-of good time to announce this, because this years ice has temporarily stopped falling off the cliff:
My previous post contains my reasoning, and also the other bets. At some point I’ll transfer that and those to here for completeness, but just for now its getting late so I’m going to put this post up.
(this is Rob’s side of the story in his words)
There is little doubt that Arctic sea ice is on the decline. This is where William and me agree. What we do not agree on is how fast it will decline in the future.
Let me start by saying that I actually did not want to bet with William at all. I really wanted to bet with the self-pronounced ‘skeptics’, who continue to call AGW a “hoax”, want to dissolve the IPCC, are cherry-pick data that serves their beliefs and accuse this planet’s top scientist of fraud and file Freedom of Information acts to sustain their myth-creation media machine.
However, none of them want to put their money where their (big) mouth is. I made several attempts to bet with these guys, to see if they really mean what they said, but bet challenges always go unanswered. So as an advice to people out who are still arguing with climate-change deniers, offer to bet with them, and see how they try to weasel their way out with ad hominums and more allegations of scientific wrongdoing. Either way, it is clear they do not believe their own words, and instead simply repeat spin generated from their political media.
Meanwhile, in the real world, there is a real scientific debate ongoing regarding Arctic sea ice. On the one hand, there are the IPCC’s GCMs, which project an Arctic ice free summer by around 2070. GCMs project recovery of sea ice after excessive minima such as 2007, to a slow (30 year) down trend.
On the other hand, there are models of sea ice volume, which show much sharper decline than the decline in sea ice extent indicates. These models indicate that Arctic sea ice is getting thinner and thinner, to the point where (as Dr. Maslowski pronounced) it will “just melt away quite suddenly” in some summer, possibly as early as 2013.
Who to believe ?
As the amateur climate scientist, I don’t believe anything unless it is sustained by evidence. For starters, I noticed that the actual sea ice extent has been more than one standard deviation below the mean of the IPCC GCM projections, since the late 1990′s and almost two standard deviations below the mean since 2007. The question is, will it return to the GCM projected long-term term trend line, or not. Tsietsche et al 2010 and William’s own paper, both based on GCMs, project recovery. However, it seems that GCMs underestimate the ice albedo effect. In Tsietsche et al, only 25 W/m^2 in July is attributed to albedo changes, while other papers observe albedo changes as high as 125 W/m^2 in July (when open water replaces ice cover). That factor of 5 difference is a strong indicator that Arctic sea ice may not recover so easily from record lows (like 2007), but instead accellerate its rate of decline. Besides, the Arctic is a dumping ground for the Northern Hemisphere’s heat. Heat due to GHG increases will be pushed into the Arctic since that is the coldest place around. The Arctic is a heat sink since there in no colder plave around except for outer space. That’s why Arctic winters are significantly warmer than just a few decades ago and the Arctic is warming up faster than any other region on Earth. Arctic summers however cannot warm much, since sea ice prevents it from going much above 0 C. Common sense tells me that added heat will just go to melting ice. That effect should be noticeable in reduction of Arctic sea ice volume, and it is. The PIOMAS record for example shows a decline of sea ice volume minima from around 17 million km^3 in the early 80′s to as little as 4 million km^3 in September 2010. That decline is actually accellerating, and is on track to hit rock-bottom by around 2016, as this graph indicates :
Needless to say that zero volume means zero sea ice extent, which puts some merit behind Dr.Maslowski’s statement that it will “melt away quite suddenly” in some summer in the near future, which would make my projection of 3.1 million km^2 look like an immense over estimate of sea ice in 2016. Various in situ ice thickness measurements seem to confirm the PIOMAS estimates, although the gap in satellite ice thickness data (between Icesat and Cryosat) currently seriously hampers confirmation or rejection of these Arctic ice volume developments.
So this bet is really a bet between scientific models of Arctic sea ice development.
William rightfully sustains the confidence in GCMs that are the basis of the IPCC Arctic sea ice projections, while I have more confidence in the scientific findings of albedo change and Arctic sea ice volume models.
Who is right ? September 2016 will tell, or maybe earlier…
And I sure hope that I am wrong. Because if I am right, Arctic sea ice is in much worse shape than the IPCC expects it to be, with potentially disastrous consequences for Arctic wildlife and climate patterns across the entire Northern Hemisphere.
* Lab Lemming – third annual guess-the-sea-ice contest
* A Bad Bet on Arctic Sea Ice Revkin-Romm stuff