Worry....(and why you should RTFR)

Ethon met the plane this morning. The guy was rather excited, it appears that snack in trying to be snarky pointed to an interesting post in the Arxiv. For those who don't know, Arxiv is an e-preprint server where manuscripts can be made available on a rather forgiving basis. You can find almost everything there for many fields of physics, especially high energy and theory, but increasingly condensed matter (aka solid state), chemistry and other folk are using it. It is both a place holder for new results while the referees take their GD time (Happy Bunny on such referees You know who you are, REPENT), and a place for the scientific equivalent of an op ed.

James Hansen provides the technical version of public presentations he has been making about ice sheet collapse. The abstract clearly labels this a polemic

I suggest that a ‘scientific reticence’ is inhibiting communication of a threat of potentially large sea level rise. Delay is dangerous because of system inertias that could create a situation with future sea level changes out of our control. I argue for calling together a panel of scientific leaders to hear evidence and issue a prompt plain-written report on current understanding of the sea level change issue.

Hansen argues that those who study glaciers are aware of the dangers of ice shelf collapse and the increasing evidence for it, but because they are not absolutely sure of this are reticent to say much about it. He considers this very dangerous, because of the threat from such a collapse. Going into issues of motivation is always a murky sea, and, of course, it is the only thing that the Boulder pack bays after.

NASA's Jim Hansen has discovered STS (science and technology studies, i.e., social scientists who study science), and he is using it to justify why the IPCC is wrong and he, and he alone, is correct on predictions of future sea level rise and as well on calls for certain political actions, like campaign finance reform.

Someone has evidently not RTFR. Hansen also marshalls evidence about increasing melting

The area with summer melt on Greenland increased from ~450,000 km2 when satellite observations began in 1979 to more than 600,000 km2 in 2002 (Steffen et al 2004). Linear fit to data for 1992-2005 yields an increase of melt area of +40,000 km2 per year (Tedesco 2007), but this rate may be exaggerated by the effect of stratospheric aerosols from the 1991 volcanic eruption of Mount Pinatubo, which reduced summer melt in 1992. Summer melt on West Antarctica has received less attention than on Greenland, but it is more important. Satellite QuickSCAT radiometer observations reveal increasing areas of summer melt on West Antarctica and an increasing melt season length during the period 1999- 2005 (Nghiem et al 2007).

also

The most compelling data for the net change of ice sheets is provided by the gravity satellite mission GRACE, which shows that both Greenland (Chen et al 2006) and Antarctica (Velicogna et al 2006) are losing mass at substantial rates. The most recent analyses of the satellite data (S. Klosco et al priv. comm.) confirm that Greenland and Antarctica are each losing mass at a rate of about 150 cubic kilometers per year, with the Antarctic mass loss primarily in West Antarctica. These rates of mass loss are at least a doubling of rates of several years earlier, and only a decade earlier these ice sheets were much closer to mass balance (Casenave 2006).

and much more. But, of course, why engage with evidence. It is instructive to see how science policy studies deals with this by Hansen

‘Scientific reticence’ leapt to mind as I was being questioned, and boxed-in, by a lawyer for the plaintiff in Automobile Manufacturers versus California Air Resources Board (Auto Manufacturers 2006). I conceded that I was not a glaciologist. The lawyer then, with aplomb, requested that I identify glaciologists who agreed publicly with my assertion that sea level was likely to rise more than one meter this century if greenhouse gas emissions followed an IPCC business-as-usual (BAU) scenario: “Name one!”

I could not, instantly. I was dismayed, because, in conversation and e-mail exchange with relevant scientists I sensed a deep concern about likely consequences of BAU global warming for ice sheet stability. What would be the legal standing of such a lame response as ‘scientific reticence’? Why would scientists be reticent to express concerns about something so important?

Gets translated into Bouldarese:

What evidence does Dr. Hansen provide to indicate that his views on sea level rise are correct and those presented by the IPCC, which he openly disagrees with, are wrong? Well, for one he explains that no glaciologist agrees with his views (as they are apparently reticent), suggesting that in fact his views must be correct

which is kind of like being savaged by a dead sheep, of course you have to RTFR to enjoy your mutton. Hansen's manuscript is an introduction to the growing discussion between glaciologists and other climate scientists about ice system dynamics

However, if these IPCC numbers are taken as predictions of actual sea level rise, as they have been by the public, they imply that the ice sheets can miraculously survive a BAU climate forcing assault for a period of the order of a millennium or longer. This is not entirely a figment of the IPCC decision to provide specific numbers for only a portion of the problem, while demurring from any quantitative statement about the most important (dynamical) portion of the problem. Undoubtedly there are glaciologists who anticipate such long response times, because their existing ice sheet models have been designed to match paleoclimate changes, which occur on millennial time scales.

However, Hansen et al (2007) show that the typical ~6ky time scale for paleoclimate ice sheet disintegration reflects the half-width of the shortest of the weak orbital forcings that drive the climate change, not an inherent time scale of ice sheets for disintegration. Indeed, the paleoclimate record contains numerous examples of ice sheets yielding sea level rise of several meters per century, with forcings smaller than that of the BAU scenario. The problem with the paleoclimate ice sheet models is that they do not generally contain the physics of ice streams, effects of surface melt descending through crevasses and lubricating basal flow, or realistic interactions with the ocean.

Rahmstorf (2007) has noted that if one uses observed sea level rise of the past century to calibrate a linear projection of future sea level, BAU warming will lead to sea level rise of the order of one meter in the present century. This is a useful observation, as it indicates that sea level change would be substantial

with a technical bottom line of

The nonlinearity of the ice sheet problem makes it impossible to accurately predict sea level change on a specific date. However, as a physicist, I find it almost inconceivable that BAU climate change would not yield a sea level change measured in meters on the century time scale. The threat of large sea level change is a principal element in our argument (Hansen et al 2006a,b, 2007) that the global community must aim to keep additional global warming less than 1°C above 2000 temperature. In turn, this implies a CO2 limit of about 450 ppm, or less. Such scenarios are dramatically different than BAU, requiring almost immediate changes to get on a fundamentally different energy and greenhouse gas emissions path.

and a science policy recommendation

In this circumstance it seems vital that we provide the best information we can about the threat to the great ice sheets posed by human-made climate change. This information, and necessary caveats, should be provided publicly, and in plain language. The best suggestion I can think of is for the National Academy of Sciences to carry out a study, in the tradition of the Charney and Cicerone reports on global warming. I would be glad to hear alternative suggestions.

Which, of course, is wildly extreme.