So may thoughts and idea, yesterday, that finding one object of focus was in the end impossible.
Looking at Tim Lenton’s article on ‘tipping points’, the most likely candidate for irreversible change sooner rather than later is the Greenland Ice Sheet (GIS). This is based on the best estimates for inducing persistent melting in excess of accumulation as perhaps not more than a 1-1.5C change in the global mean temperatures from the present. As always, there are many other factors to consider, but allowing that they have been considered, the chances of global temperatures rising by this amount in this century are extremely good, and as an outlier, the chance of a sufficient warming to bring the process to the ‘edge’ happening in the next twenty or thirty years is not trivial.
As is clear from current conditions and recent satellite measurements, we cannot ignore the possibility that we are closer to a persistent, if not irreversible, reduction of the GIS than most estimates allow for; there is a small chance that we are already seeing the ‘beginning of the end’. If we accept that no change in emissions policy will operate rapidly enough or soon enough to prevent further warming of at least 1C and, more plausibly, not less than 2C over the coming decades, then the conclusion that the GIS will reach a ‘tipping point’ this century does not seem unreasonable.
EDIT: See, for example, Fettweis, The Cryosphere Discussions.
Then there is the important question of rate of melt. Hansen (2007) reckons that 100 years could see the loss of the majority of the GIS and consequent sea level rise. Lenton allows at least 300 years. Previous estimates of 1000 years seem to be increasingly less likely, as the recent rate of changes in the Arctic encourages science to review its estimates of how quickly such massive changes could, in principle, happen.
Estimates put global sea level rise at 6 meters or so if the GIS melts completely. There surely would be no argument that a six-metre rise in a hundred years would be ‘catastrophic’, even a six metre rise in a semi-smooth curve (there is some evidence that SL ‘hops’ rather than increases smoothly in response to such changes) over 300 years is not to be easily pushed aside. Though this might add only 30cms by 2100 to other factors causing sea level rise, and maybe 75 cms by 2200, thiss added to the IPCC’s (almost certainly conservative) estimate of 57+- 20, excluding the GIS, by 2100, gives us close to a metre this century and more than two metres by 2200. Allowing for tidal ranges and storm surges, a one metre rise could result in local rises under the right conditions of 6-10 metres, or 20-30 feet; more than enough to overwhelm existing flood defences in most palces on the globe. A two metre rise places at least six megacities at risk of sufficient inundation as to render them no longer viable as centres of commerce or habitation. London is one of these cities.
None of the above considers the side effects of such scenarios, which in themselves may well be significant. What, for example, do we expect to happen to the people of Bangladesh, if the third of their country which is already marginal due to seasonal flooding then becomes uninhabitable? Are we to leave them to deal with the problems arising? Do we expect thirty million or more people to simply sit and wait to die? Where, if not Bangladesh, are these people to find a home?
One side-effect occurred to me which I haven’t seen discussed (which doesn’t mean that it hasn’t been, so if you know, please tell me…) is the Geological implications of a mass balance shift on the scale of a loss of the GIS. It is reasonable, surely, to expect such a huge loss of mass over such a large area to result in shifts in the tectonic plates, if not a global, then at least a regional-scale readjustment. Add to this the relative increase of pressures from great volumes of water elsewhere, and the likelihood of some kind of adjustment seems to increase.
What would be the consequences of this? At least earthquakes, and probably new and violent volcanic activity, might plausibly be expected. Then you add this risk into the mix of risks which have already been added up. And then you add the feedbacks into the climate system and the regional earth system. I don’t know what might or might not happen, but I’d be interested to find out how much this particular matter has been considered.
Then there were the thoughts about public doubts about climate change. The Sterman articles provided by Steve Bloom seem to attribute inaction or misunderstandings about the need for mitigation broadly to various kinds of ignorance. Whilst I agree that ignorance is a characteristic of much scepticism, it is also manifest in the more common stance of acceptance and concern about climate change. As such, it is probably not a sufficient, or a necessary, condition for scepticism. It is also important to note that scepticism is also an attitude amongst some intelligent and well-informed people, including a small number of scientists.
The psychological approach of Climatedenial.org is attractive in some ways, but also – and this is more intuitive – does not feel adequate to explain the response of those who have decided that CC is not the problem that many others believe it is. This, in turn, led to the observation, which is probably trivially true, that there are at least two distinct brands of scepticism, which therefore probably have different derivations and thus require different treatment. As the dominant form in terms of number is the ‘reasonable doubt’ of those members of the general public who aren’t willing to bow to peer pressure and simply accept what they are being ‘fed’ by the media, this is the form which most needs attention.
I have previously approached this doubt by asking why people feel this way and then working through the responses, but this has a limited effect; whilst some recognition can be generated that some at least of the causes of doubt are irrational, yet still the doubters return to their default position. So I am going to experiment with a different approach, which is to examine these doubts in terms of underlying needs/ absences/ fears. If we can identify the object if dissatisfaction in this way, much as Advertising agencies seek to identify a need or absence which a product can satisfy, in the absence of competition, then we may be able to find a ‘product’, in terms of communication, which provides a doubter with the missing element, and thus encourages her or him to actively reconsider and then adjust her or his behaviour.
That’ll do for now. Be good.