Having recently apparently managed to give the impression to some people that I am anti-science, and with the general note that bodies such as the IPCC are somewhat vilified even amongst portions of the scientific community, I thought some debate around what we take as relevant science might be illuminating.
A view expressed by another person in another thread was that we should consume the conclusions of bodies of "experts" with respect to climate change (with the implication that personal speculation and progression along the spectrum of expertise was irrelevant and unhelpful).
I wanted to - in the specific context of arctic sea ice (but with the note that the same principles apply to a great number of other earth system predictions with respect to anticipated effects and timescales thereof from climate change) raise this as something worth a closer examination.
Perspective 1My impression is that the mainstream scientific community has consensus views little shifted from 2007 - predicting total Arctic sea ice loss later this century (certainly not within the next few years, and - on average - not even without the next few decades). This is a recent paper appearing to state that very conclusion:
http://www.pnas.org/content/early/2013/07/10/1219716110IPCC AR4 doesn't really appear to predict total ice loss this century:
http://www.ipcc.ch/publications_and_data/ar4/wg2/en/ch15s15-3-3.htmlhttp://www.ipcc.ch/publications_and_data/ar4/wg2/en/figure-15-3.htmlAlthough Neven is picking holes in it in this example, it contains the necessary quotes to illustrate that AR5 is likely to be similarly conservative:
http://neven1.typepad.com/blog/2012/12/the-real-ar5-bombshell.htmlThe Hadley Centre (Met Office) weighed in - they expect later century ice loss also, as predicted by their models - this article contains their views as to why projections of near future ice loss ought to be discarded and ignored:
http://www.guardian.co.uk/environment/2009/feb/11/climate-change-misleading-claimsAll of the above, I argue is
mainstream science. It is mainstream because it reflects the typical view held by the public, by policy makers and by the scientific community at large (noting that most scientists are not experts in any arbitrarily selected field, in this case sea ice, as science is a vast entity).
It is a matter of public record that the models used to attempt to predict these things are still incomplete and still advancing quite fast (indicating a long way to go, if I might be cynical).
Perspective 2Observational evidence, which I submit is still
science appears to indicate that the models are not accurately predicting the state of the Arctic (notwithstanding that these models usually take base runs starting well over a century ago historically and are actually
only off by a few decades - something fairly pointed out to me by someone defending the modelling community - my counter point was that those decades really matter once you're inside them)
We have measurements by satellites (which I would hope most people using this forum are familiar with as I don't want to have to compile a list). We also have corroboration from ground measurements - sometimes that actually suggest that the satellites appear to be painting a somewhat more rosy picture than what's going on at ground level.
I can't remember where I came across this (might have been this forum):
http://home.cc.umanitoba.ca/~dbarber/David_Barber/Sea_Ice_Research_files/Barber_etal_GRL%2709.pdfBetween PIOMAS and Cryosat 2 it seems reasonable to state that ice volume has crashed and is continuing to decline precipitously with very little time left for any negative feedbacks to put a floor under ice loss before we start to see ice free conditions in the Arctic for part of the year. It is very hard to see how the ice can persist perennially for decades to come given that the pressure on the ice is increasing over time as greenhouse gases continue to be released and the warming from already released gases continues to build (noting lag in the climate system in this respect).
There are multiple experts (and I use that word strongly) in the field of sea ice who have lent their name to near future predictions for total ice loss. This is also science - in the sense that it is presumably based upon extensive expertise and knowledge with the science, even if it is not precisely mainstream.
Professor Peter Wadhams -
http://www.guardian.co.uk/environment/2012/sep/17/arctic-collapse-sea-iceProfessor Carlos Duarte -
http://theconversation.com/final-frontiers-the-arctic-12911Dr Wieslaw Maslowski -
http://www.bbc.co.uk/news/science-environment-13002706I feel it is worth noting that if the climate models in Perspective 1 are failing to accurately predict the loss of the sea ice, they are also failing to accurately predict knock on consequences of losing the sea ice. That is to say that there are at least two sources of possible errors from the models:
1. The models may well have failed to capture key details that cause things to happen faster than expected as apparently with the sea ice
2. The models may capture some processes accurately but nonetheless fail to predict timescale as the forces driving these processes do not occur within the models until much later
It seems in little doubt to me that the experts in the field of sea ice being quoted above do not subscribe to the consensus mainstream views in perspective 1.
The Big QuestionWho do we listen to?
I choose to go with what observations appear to be saying, and I tend to take a more pessimistic view. I do believe a pessimistic view is justifiable in terms of the surprises the earth system has sent our way so far, and am unclear what process could meaningful delay (by more than a matter of years) total ice loss during the Arctic melt season.
Bodies such as the IPCC may say numerous events are very unlikely, but also acknowledge the uncertainties and limitations of their methods. That is ignoring the statistical near certainty that if you have enough very unlikely events to pick from - at least some of them
will happen.
I've chosen sea ice as the terms of reference for this debate about which part of science we listen to - and want to be clear that I do not listen so much to mainstream science as to what the experts in the specific field in question are saying (this is perhaps where I offended some people in another thread).
I think this is a relevant debate not only to examine more closely the portions of the scientific spectrum we base our views on - but also to explain why I (and possibly others, who I won't claim to speak for) take an outlook sometimes generously described as pessimistic (and sometimes insulting described as much worse things).
It's also relevant to help identify when alarmist and apparently extreme statements are justifiable.
Perspective 1 or Perspective 2? Is there any middle ground?