Just when you thought it might be safe to go back to reading the papers without climate catastrophism leaping out at you and grabbing you by the throat (Guardian and Independent excepted), along comes the Daily Mail to warn us that London and New York could be under water in just 50 years!
“Most scientists agree that sea levels will rise, but some say it won’t happen for centuries. Now, a new study suggests sea levels will increase several feet over the next 50 years.”
The ‘new’ study turns out to be Hansen et al’s ultra alarmist sea level rise paper published for discussion in July last year. It appears that it has now been accepted and published here.
The author of the Fail article doesn’t know their feet from their metres. According to the actual paper, within 50-150 years, sea level could rise several metres. It’s worse than we thought. Oh my God you think. Why? How? Well, it’s quite simple really. During the last interglacial (the Eemian), sea levels were much higher (6m-9m) and, I quote:
“Eemian sea level is of special interest because Eemian climate was at most 2C warmer than pre-industrial climate, thus at most 1C warmer than today. Indeed, based on multiple data and model sources Masson-Delmotte et al. (2013) suggest that peak Eemian temperature was only a few tenths of a degree warmer than today. The Eemian period thus provides an indication of sea level change that can be expected if global temperature reaches and maintains a level moderately higher than today.”
This is a gross oversimplification which is repeated in the actual paper. It is now generally accepted that mid to high latitude Northern Hemisphere temperatures during the early part of the Eemian were several degrees higher in most areas than they are today. This was due to orbital forcing – increased solar radiation (relative to today) in northern latitudes during summer. A paper very recently published suggests that temperatures in Greenland during the last interglacial peaked at 7C-11C above what they are today. So fairly obviously, the melting of the Greenland Ice Sheet contributed at least partly to rising sea levels during the Eemian (which, it must be pointed out, was far from a uniform increase – indeed, sea levels may have risen and then dropped in two or more pulses throughout the entire interglacial.
It may be the case that average global temperatures during the Eemian peaked at no more than 1-2C above the pre-industrial Holocene, but this conclusion seems dubious – quite how one measures average global temperatures over 100,000 years ago with this degree of accuracy, I have no idea. We are not even certain what the actual global mean surface temperature was 150 years ago, let alone 100k!
Hansen’s argument for comparing the Eemian sea level rise(s) with what may happen in the next 50-150 years rests on a complex theory involving rising CO2 and its effect on the West Antarctic Ice Sheet which he postulates underwent a collapse in the late Eemian when orbital forcing of Northern latitudes was decreasing and global temperatures were declining:
“Our climate simulations and analysis of paleoclimate oscillations indicate that the Southern Ocean has the leading role in global climate change, with the North Atlantic a supporting actor. The Southern Ocean dominates by controlling ventilation of the deep-ocean CO2 reservoir. . . .
The most important practical implication of this “control knob” analysis is realization that the timescale for ice sheet change in Earth’s natural history has been set by CO2, not by ice physics. . . .
However, sea level rise itself is the single greatest global concern, and it is now broadly accepted that late-Eemian sea level reached 6–9 m, implicating a substantial contribution from Antarctica, at a time when Earth was little warmer than today.”
The problem is, though Eemian sea level estimates may be ‘broadly accepted’ to be 6-9m, they may have been rather less and the relative contribution from Greenland (due to orbital forcing of the ice sheet in summer) may have been rather more, which kind of pours cold water on Hansen’s CO2 alarmism. In this respect, there is an interesting Short Comment on Hansen’s paper from Matt Whipple at Bristol University, some of which I quote below:
“More to the point, Eemian temperature data shows a clear lead in the Antarctic records . . . . . . The maximum Greenland contribution was late Eemian, as shown by multiple modelling studies (e.g. Stone et al., Clim. Past, 2013), and ice core gas content elevation proxy data (NEEM community members, Nature, 2013). Given the timing of both Greenland temperature and ice sheet response, it is most plausible that the second peak in sea level data was sourced from Greenland . . . . . there remains no evidence for Eemian WAIS collapse.”
It’s fair to say that Hansen’s paper has generated a lot of comments from other scientists, many of them not very positive. Credit to ACP for making them public here. Drijfhout of Southampton University comments here. Among other criticisms, he says:
“The Eemian cannot be directly compared to any future climate that we might anticipate.”
Peter Thorne of Maynooth University writes a 32 page rather damning review here. Thorne is definitely not impressed with Hansen of whom he comments that his response to criticism was “unprofessional” and “grossly inappropriate”. Furthermore, he says:
“I expect this kind of thing of my kids. I do not expect this behaviour to be out there in the public domain for all to see amongst leading scientists in the field.”
As for the apocalyptic picture painted, Thorne said it was “marginally more likely than me or you buying a winning Euromillions [lottery] ticket today”.
All in all then, I think we can safely say that London and New York won’t become prime attractions for scuba divers within the lifetime of our children or our grandchildren.
Shame on the Daily Mail for running with this nonsense but they do at least provide some counterpoint to the ridiculous headline and the bulk of the text – from Michael Mann no less:
But others still remain hesitant about the claims made in the draft paper, released last year, and are still on the fence with the final version.
‘Some of the claims in this paper are indeed extraordinary,’ said Michael E. Mann, a climate scientist at Pennsylvania State University. ‘They conflict with the mainstream understanding of climate change to the point where the standard of proof is quite high.’
Making quite a name for himself is Mann, refuting the more extreme claims of his colleagues – first he co-authors a paper saying the Pause is real, and now this.