Thursday, March 29, 2007

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.

25 comments:

Anonymous said...

And once more Rabettology shows itself to be spot-on in identifying the trap of BAU. Not BAU of emissions, but the BAU of SAU--science as usual has shown itself to be less than robust in dealing with the challenges of a global "situation" unlike any we have experienced as a civilization.

Anonymous said...

BAU = Boulder As Usual?

Provide an inaccurate summary and condemn the author based on the meaning of that summary.

Adam said...

Seems that Hansen's not the only one raising concerns. First* there's the post on RC then there's:

http://www.jsg.utexas.edu/walse/statement.html



(*in the order that I read them)

fergus brown said...

I want to know what we are meant to understand by the term 'collapse'. It conjurs images of a Larsen-type crack and float-off, but I don't think this is what is expected of the WAIS, for example. Does the term refer to a point at which sudden and massive changes occur almost immediately, or to a system-state which represents a tipping-point, beyond which certain (relatively slow) processes are irrevocable?
IOW, what does a 'collapse' of the ice sheets mean?
Regards,

Anonymous said...

Wouldn't it be nice to be able to divine motivations the way Roger Pielke does?

I used to wonder how he does it, but that's a little like wondering how string theory works.

Better not to worry about how it works and just be thankful that it does.

Anonymous said...

"I want to know what we are meant to understand by the term 'collapse'."


I think you must look at the context in which Hansen has used the term "collapse" to determine the meaning, being careful that you do not apply it outside that context (ie, to mean something that Hansen may not have intended).

For example, in the paper linked to above, Hansen makes it pretty clear what he means by collapse -- but also makes it clear just what is collapsing:

"Combined actions of surface melt (van den Broeke
2005) and ice shelf thinning from below (Shepherd et al 2003) led to sudden collapse of the Larsen B ice
shelf, which was followed by acceleration of glacial tributaries far inland (Rignot et al 2004; Scambos et
al. 2004). The summer warming and melt that preceded ice shelf collapse (Fahnestock et al. 2002;
Vaughan et al 2003) was no more than the global warming expected this century under BAU scenarios,
and only a fraction of expected West Antarctic warming with realistic polar amplification of global
warming."

Anonymous said...

It is also useful to note with regard to my above comment that in another place in the same paper, Hansen uses a different word to refer to ice sheet changes:

"Mercer (1978) suggested that
global warming from burning of fossil fuels could lead to disastrous disintegration of the West Antarctic
ice sheet, with sea level rise of several meters worldwide."

Note the word "disintegration" (as opposed to "collapse"). It is possible of course, that the word disintegration was Mercer's, but it also appears that Hansen is pretty careful about his terminology and the specific cases to which it applies.

fergus brown said...

Thanks for your response, anonymouse. Little as I understand the dynamics or the geology, I don't get how the whole WAIS is supposed to detach itself & float off, all at once. Rapid calvings, glacial outflow increases, subglacial runoff; fine, but the whole kit and kaboodle? Nah.
If anyone knows any better, please let me know.
Perhaps I'll email the good prof. & ask him.
regards,

Anonymous said...

It is interesting to compare and contrast Hansen's "gut" feeling with that of Kevin Vranes -- not just for content and meaning, but for the way it was received by Pielke.

Here's Hansen:

"I suggest that a ‘scientific reticence’ is inhibiting communication of a threat of potentially large sea level rise."

Hansen bases his gut feeling on "conversation[s] and e-mail exchange[s] with relevant scientists [in which] I sensed a deep concern about likely consequences of BAU global warming for ice sheet stability"


Here's Vranes:

"What I see is something that I am having a hard time labeling, but that I might call either a "hangover" or a "sophomore slump" or "buyers remorse." And now we're wondering if we didn't create a monster. ....We wonder if we've oversold the science."

Vranes based his assessment on conversations he had with a small number of scientists at the anual AGU conference:
"I will grant that talking to the people I did at AGU represents a small fraction of all the attendees. I will grant that there is no way to know whether my averaging of attitudes in the climsci world, as sensed by talking with a few people over a few days, scales up to represent the true feelings of the collective."


http://sciencepolicy.colorado.edu/prometheus/archives/climate_change/001030so_what_happened_at_.html

There is the obvious question of "who is closer to the pulse of the climate science community" -- Based on number of peer-reviewed papers and collaborations with other climate scientists over the years (including many in IPCC), I'd have to conclude that Hansen probably has a better feel for the pulse than does Vranes.

But quite apart from that, there is also the question as to how these two statements (which are quite similar in feel if not meaning), were received by the Oracle of Science Policy: Roger Pielke.

Pielke immediately jumped on Hansen:

"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."

But where is Pielke's equivalent call for evidence from his colleague Vranes after he made his "We wonder if we've oversold the science" comment ?

Surely, If Pielke is going to give Vranes the benefit of the doubt with regard to his "We wonder if we've oversold.." comment, based on little more than a few conversations at AGU, than he should also give Hansen a little more slack about his conclusions based on conversations and e-mails with actual working climate scientists.

There would appear to be a glaring double standard here on the part of Pielke.

Anonymous said...

Fergus brown said: "Little as I understand the dynamics or the geology, I don't get how the whole WAIS is supposed to detach itself & float off, all at once."

Good lord, where does Hansen say that???

Please post the reference when you locate it.

fergus brown said...

anonymous: assuming you're a different anonymouse to the previous one, a brief look at posts 4,6,7 & 8 above should explain the context. If Hansen is using the term collapse to imply a Larsen-type event, then that is what we might expect to see. I don't think that is what is meant by the term, but as the other anonymouse pointed out, it does appear to have been implied. Does that help?
regards,

Steve Bloom said...

Fergus, the three ice sheets (GIS, WAIS and GIS) exist in quite different circumstances. The GIS would be most vulnerable to rapid collapse, but its geography (much of it ringed in by mountains with relatively narrow outlets) would probably force it to melt in place to a great extent. The situation of the WAIS is simpler: It's grounded below sea level and is substantially open to the sea. This makes it vulnerable to undermining by ocean currents in combination with surface melt effects, both of which are being seen now. Probably the key point to bear in mind is that its geography makes it possible for the WAIS to break up and float off without much bulk melting having occurred in place.

My understanding is that much of the reason for the reticence of the glaciologists (although that may be changing per the statement linked above) is that the various bulk melting effects have been observed on the GIS and WAIS so recently that it has not been possible to develop any kind of model. Hansen believes that if we know enough to say that BAU melting will occur much sooner than previously thought, that's enough to go public with. As always, he's right. I think we can expect to see that NAS panel announced real soon. Anybody want to give odds as to whether RP Jr. will be asked to be a member?

Steve Bloom said...

Just to add that the Larsen break-up took place in a matter of weeks, and I don't think anyone imagines that the WAIS could do anything like that. I would expect (remembering that my opinion has little value) years at least, and more likely decades, for a worst-case break-up. The consequences of it happening even over the course of one or two centuries would of course be quite horrible.

Hank Roberts said...

This is an area obviously in need of attention.

Peiser and Peilke seem to ignore what the scientists working in the IPCC said --- that the 2007 report does not address recent science on sea level rise, because it's come in after the deadline for the 2007 document.

I'd think ignoring this blows up the "honest broker" self-advertisement --- responsibility to address new info would apply to any broker, I'd hope, same as it applies to accountants giving opinions about companies so the old info not be used to defraud.

Good to see Hansen's taken the lead in suggesting this be addressed before the, what's the next one, 2012? IPCC comes out.

Anonymous said...

Fergus said: "If Hansen is using the term collapse to imply a Larsen-type event, then that is what we might expect to see."

Actually, you have to look at how Hansen has actually used the term collapse for a specific context -- ie, for a particular ice sheet.

That was my point, not to imply that Hansen's use of the term for the Larsen Ice Shelf could be applied (in Hansen's mind) to the West Antarctic Ice sheet as well, which Hansen actually referred to as a "disintegration".

I think you really need to be careful about looking at the way Hansen himself actually uses the term "collapse" and not how Eli and others might use it.

Anonymous said...

"Peiser and Peilke seem to ignore ... that the 2007 report does not address recent science on sea level rise,"

If the Sun burns out in our solar system and there is no IPCC report to make it official, does it have an effect?

EliRabett said...

Hi, I'll post more on this tonight, but I take Hansen's use of collapse to mean the irretrevable loss of structural integrity of the ice sheet which will lead to disintegration on a faster than millenial time scale (hows them for science speak bucky). This translates into sea level rises of meters in roughly the number of centuries that three finger Brown could count.

Anonymous said...

Pielke implies that Hansen somehow just recently discovered "science policy".

I think not. Hansen plays the game like a seasoned pro -- and he is in peak form.

Pielke can only dream about one day playing at that level.

I think there is more than a little jealousy involved.

Hank Roberts said...

I left some, er, gleanings here:

http://scienceblogs.com/stoat/2007/02/why_do_science_in_antarctica.php#comments

As I found articles about changes in what we know about how fast the ice caps can change -- there's been a surprisingly _large_ number of very recent reports --- over the last few weeks.

(Why there? it was roughly on topic, and because I appreciate the corrections I get there. Probably no surprises for those well read in this, but maybe.)

The last of the posts I left there included this bit:

"... early conclusions drawn by geologists at Andrill (Antarctic Geological Drilling), the multinational consortium leading the project, which recently released preliminary data from the drilling on its Web site. ...
"This time we were able to drill into layers representing the period between five and 12 million years ago," Andrill team member and geologist Lothar Viereck-Götte told SPIEGEL ONLINE. What these unique ice cores revealed about temperature changes in the last 5 million years was both surprising and new, says Viereck-Götte, who calls the results "horrifying." The data suggests "the ice caps are substantially more mobile and sensitive than we had assumed."
That's from:
http://www.spiegel.de/international/0,1518,469495,00.html

Anonymous said...

What I find most surprising is that some people can be so certain that the ice sheets will go slowly.

This is actually contrary to everything one sees in microcosm every winter. Once ice starts melting, it goes fast, so long as the temperature remains warm.

Furthermore, anyone who has traveled on glaciers in the spring or summer knows (or at least better know) that there is a lot going on under the surface that is not visible from above -- a lot of undermining of the ice pack that one has to be very careful of when one is crossing the glacier.

Giant crevasses can open up in a relatively short time period as the ice moves and rivers flowing under the glacier can hollow out great caverns under the ice which tend to undermine the structure above. Melting does not occur only (or even primarily) from outside in as many seem to assume.

based on my mountaineering experience on glaciers, I have little doubt that Hansen's instincts are probably correct on the ice issue.

Once those ice sheets start going (collapsing, disintegrating, whatever you want to call it), they are going to go fast and there will be nothing we can do about it.

Anonymous said...

says Viereck-Götte, who calls the results "horrifying." The data suggests "the ice caps are substantially more mobile and sensitive than we had assumed."

Andrill co-chief scientist Tim Naish, of GNS Science, said the drill cores had already shown some interesting history of the Ross Ice Shelf.

"They reveal that the ice sheet has advanced and retreated more than 50 times during the past five million years. Some of the disappearances of the ice shelf were probably during past eras when the planet was a few degrees warmer than it is today

http://www.gns.cri.nz/news/release/20061220_andrill.html

Yes finding that they advance and retreat every 10000 years would be horrifying

Fergus Brown said...

No, anonymouse, once every 10000 years or so wouldn't be too much to worry about. Perhaps evidence that the ice sheets disappeared in response to temperatures only a few degrees above those we are now experiencing might be a cause for concern, though, if we thought that the temperature was, for whatever reason, going to continue rising for a few more decades, or centuries.
Regards,

Anonymous said...

Fergus: Based on what has happened in the past, there is good reason to believe that "ice sheets disappeared in response to temperatures only a few degrees above those we are now experiencing."

According to Hansen (from his "Scientific reticence and sea level rise" paper linked to by Eli)
"Global mean temperature three million years ago was only 2-3°C
warmer than today (Crowley 1996; Dowsett et al 1996), while sea level was 25 ± 10 m higher (Wardlaw
and Quinn 1991; Barrett et al 1992; Dowsett et al 1994).

fergus brown said...

I know. I don't think the irony translated well. It was a response to the previous mouse.
Regards,

ankh said...

Thanks for that link to the NZ article about Andrill.

Andrill's website is lagging a bit; their last 'update' was when they had something stuck and the scientists were waiting around against their departure deadline.

Their "Calendar" includes these, if anyone's going:

ANDRILL's calendar.

MIS Post-Drilliing Workshop
May, 2007
Florida State University

M-ASIC Meeting
May, 2007

EGU Meeting
April, 2007

ANDRILL Representation at National Science Teachers Association Conference
April, 2007
St. Louis, MO


--- Hank Roberts
migawd, google seems to be letting me use the Blogger id again, this time