Let me guess, some characters with poor reading comprehension will see the word ‘collective’ as ‘commie’ and the word ‘frame’ as ‘intellectual terrorism’ and use that to justify their ideological baloney, Jack.
A most revealing ad hom response. When climate science communicators start calling for help in “reframing collective thinking,” and saying that “openmindedness is the wrong approach” (Naomi Oreskes), it may be time to re-examine the science itself.
[Response: Brilliant logic. Not only do you not know what ad hom means, but your response completely supports Haver’s original comment. On top of that, apparently arguing that the radiative properties of CO2 are somehow tied to your mis-understanding of an op-ed in the Los Angeles Times is delicious. Should gravity be questioned based on comments on NBC? The germ theory of disease because of a guest on the Today Show? Please try and do a little better. – gavin]
Perhaps Wikipedia can help Gavin understand what ad hom means: ”Abusive ad hominem (also called personal abuse or personal attacks) usually involves insulting or belittling one’s opponent in order to attack his claim.” Havers’ slurs (“poor reading comprehension” “ideological baloney” – this last a juvenile twist at my name) and mischaracterization of my comments are clearly abusive ad hominem attacks.
The remainder of Gavin’s comment makes no sense at all, as I did not argue anything about “radiative properties of CO2” nor draw any conclusions from Naomi Oreske’s op-ed piece. I only asked if the statements were good examples of climate science communication. It’s is amazing – and rather depressing – to see how an honest question draws such vitriolic responses at RealClimate.
[Response: You also misunderstand the definition of the word ‘vitriolic’. But really, either say something substantive and on topic or don’t bother. – gavin]
Is there a scorecard somewhere? It might be helpful to have a list of predictions or forecasts and some indication of how they turned out.
[Response:Everyone: This is a very simple, news-type post; comments here should be strictly on topic. Please take all non-relevant conversations to the open thread. Previous off topic comments have been moved there. The management thanks you in advance.]
The use of the word ‘collective’ here does illustrate a point about communication. That is: Don’t accidently blow other peoples’ dog whistles. I remember listening to Ray Bream on talk radio back in the 80’s as he trained his listeners on certain key words. In this case, he played a fairly innocuous audio clip of somebody saying something he didn’t like, and then he jumped on the word “struggle” as indicating that the speaker was a Communist; because (he said) it’s a word that all radical lefties always use when they’re up to nefarious plots.
It helps to develop a sensitive ear for how others hear if you don’t want to make distracting noises. Choose your words like a poet. Just as in a visual artist’s training, critique sessions include some focus on weeding out the accidental associations that tend to crop up in the design process and that weaken the overall impact of content.
[Response:I think your comment is right on. I was a little concerned with the wording in question as well–doesn’t sound good. My bigger concern is with the assumptions and/or wording of some of the questions themselves however, which are either questionable or could lead to confusion. For example, why did they choose the year 2000, instead of a 19th century date, as the baseline against which to estimate the effects of doubled CO2–this could throw some people off–Jim]
Anyway it just goes to show, there’s no upper limit in sight when it comes to the amount of milage that one can slyly troll out of intentional misinterpretations. And I just have to note, intentional hyperbolic misconstruing is itself not conducive to civility and is particularly ironic when used to complain about a little snark.
As for the general approach of the project, there are two main parts. The first is to assess the beliefs (and distribution of beliefs) of scientists and researchers on climate risks. The second is to find ways of effectively communicating this information in an understandable and usable way to policymakers and the public.
Please feel free to send us your comments, criticisms and/or suggestions on how to improve the project.
–Peter Kriss, Vision Prize Director of Research
[Response: Peter. Thanks for stopping by RealClimate. I see you have changed the question about sea level a bit, perhaps in response to my comment, but the new version is also problematic. You have “What is the likelihood that global average sea level will rise more during this century than the current worst-case scenario of the Intergovernmental Panel on Climate Change?” Perviously, this was give as ’18 to 59 cm’. But these are not ‘worst case scenarios. They are essentially best case scenarios, because the entirely the impact of dynamic ice sheet changes. The uncertainty is large but the sign is almost certainly positive. IPCC was very clear about this: they didn’t feel at the time that they could quantify the high end because too little was (and is) know about the dynamic response of ice sheeets.
You might say “….rise more than this century than the maximum end of the range given in the 2007 assessment Intergovernmental Panel on Climate Change (that is, 59 cm by centuries end, not account for ice sheet dynamics).”? Of course, that gets a little complicated. You could instead just say “…rise more than 50 cm” and leave it at that. –eric]
Thanks for posting the link to the questions, though I’m pretty sure I will not be answering the questionnaire. I guess the registration is just for avoiding extreme reactions by denialists. Anyway, here’s one of my answers (and some are worse). I don’t think they’d serve any purpose wrt the policy discussions, specially because I’m not from North America.
” What will be the total number of major hurricane landfalls in the U.S. from 2011 to 2020? From 2041 to 2050?”
Paradoxically the number will be smaller during the 2041-2050 since the subtropical high will be too strong over the south states making agriculture there near impossible. The storm tracks will be more northern than now and will be hitting the other side of the Atlantic regularly (Spain, Morocco,France). The Greenland meltwaters will guard the NW North America coasts from direct hits better than currently though the associated rains will be more severe likening the worst events seen today.
10 Peter Kriss: Now that I have seen the questions, I am less interested in answering many of them. Some questions may be for filtering on expertise. It seems to me that to provide guidance to the public about climate risks, you would ask questions about things that would affect the public, such as:
When will Los Angelenos notice a water shortage?
When will GW cause a global famine?
Was the Russian drought of 2010 caused by GW?
Was the Texas drought of 2011 caused by GW?
When will GW get bad enough for 95% of US voters to believe in GW in spite of fossil fuel company propaganda to the contrary?
2 L. Hamilton: Or you need an address that ends in.edu or something that shows that you are working, not retired.
oops, the previous went in the wrong thread. Anyway…
” If and when CO2 concentration in the atmosphere reaches 550 ppm, what will be the increase in global average surface temperature relative to the year 2000?”
* Is there some plans to melt GIS and WAIS, since ‘when’?
Really Eric, I think you are just trying to be difficult. IPCC says we think it will rise 18 – 59 except for the stuff we don’t understand. Any intelligent human being will accept that as a range, espicially when you are only asking people if they think it will be more than that or less. You are welcome to tick the box that says more, and that is the whole aim of the survey
[Response:Actually, no, I’m trying to be precise. In fact, this is exactly the sort of problem that can make a good survey useless. The question said “IPCC’s worst case scenario”. IPCC was very clear that this was not a worst case scenario. If someone taking the survey thinks this is IPCC’s ‘worst case’, then you are inevitably going to shift the answers towards lower values than 59 cm, because of a natural reaction to be conservative. Many users of the poll will know that in fact this is not a worst case scenario, but many will either not know, or will not think about it at the time. See our write up on the IPCC numbers for sea level, here: http://www.realclimate.org/index.php/archives/2007/03/the-ipcc-sea-level-numbers/.
Thanks very much, Peter. FWIW, my non-professorial answers would be:
1. An increase of 0.8°C.
6. AR4’s highest seems about right to me. So I’d say 50%.
7. 2011-2020: seven. 2041-2050: six.
8. Of course. It’s not a technological problem.
9. There would be almost as many winners as losers, so I’ll go with one to two percent.
For my part, I don’t qualify to participate in the poll–but I did write in to suggest that they define ‘summer free of Arctic floating ice’ better. (One uses the “feedback” tab at the bottom of the Vision Prize poll page, linked above.)
[Response: It really should also make it clear whether they mean perennially free or free one time (with no implications about the year after that).–eric]
A few comments on your answers.
Regarding #1, is it your contention that natural factors have had zero effect on global temperatures?
I find your answer to #5 to be extraordinarily soon. Why is that?
I disagree with #8, in that it is largely a technology problem. Current technology cannot come close to generating the global energy requirements without emitting significant quantities of CO2. The same goes for the last answer. Without a suitable technological advancement, alternate energy production cannot be achieved without cost, which will have a greater affect on GDP.
The rest of your answers are in the same ballpark as mine.
This seems to misunderstand the climate system lag time:
“If and when CO2 concentration in the atmosphere reaches 550 ppm, what will be the increase in global average surface temperature relative to the year 2000?”
This seems to miss the concept of overshoot:
“What portion of annual global economic growth would need to be sacrificed to keep CO2 concentration in the atmosphere from exceeding 550 ppm?”
Which “annual” number are you apportioning? I think of this as an investment, not a sacrifice.
My hackles were slightly raised by the word ‘risk’ in the title, which rather poignantly reinforces the comment by Radge Havers @8.
My concern was that climate scientists were being asked for their [expert, presumably] judgement on ‘risk’, implying negative/positive impacts etc – things which I don’t think are necessarily (and certainly not exclusively) the domain of climatologists.
The poll, though, concerns itself with something quite different – to my relief. It appears well-thought out and I’m quite intrigued to see the results.
My expectation, however still leaves me with the observation that the poll trails a whole slew of assumptions that are not spelled out, that aren’t particularly the concern of climate science and which, to my mind, are very much to be debated. For instance the notion that 2 degrees of warming will be ‘dangerous’ in some vague fear-inducing way. I was greatly interested in Richard Betts comments on the subject recently. He said that he (and the majority of climate scientists) don’t subscribe to that ‘dangerous’ meme. This was partly because ‘dangerous’ is a value judgement and something science isn’t especially qualified to pronounce upon.
But, as I say, the demarcation in the poll is admirable, and I hope the participation is widespread.
> KeithWoollard says: … Eric, … trying to be difficult. IPCC says we
> think it will rise 18 – 59 except for the stuff we don’t understand.
Keith Woollard, you miss the point the IPCC was making. None of the stuff we don’t understand will reduce sea level; thus that range is better than the best case estimate — the best case will be “more than that amount, by some unknown amount.”
My own non-expert answers:
1.Increase of ~0.8 degrees C
3.~2 degrees higher (remember warming in the pipeline)
4.~1.8 degrees higher
7. 2011-2020: 20-30; 2040-2050: 20-30
9.0%. In fact, I think we could see additional growth over the long haul as energy prices stabilize and new technology spreads into the broader economy. Over the past half century, I think fossil fuels have become a source of complacency rather than a stimulus for growth.
[Response:Questions 3 and 4 only specify a certain time point, and thus appear (to me) to be asking for the transient, not equilibrium, temperature changes. This is another example of what Eric is talking about regarding imprecision of wording; it’s not trivial becuase it’s really going to affect the answers they get.–Jim]
Re Keith Woollard @ 15 “IPCC says we think it will rise 18 – 59 except for the stuff we don’t understand.”
What the IPCC report said was a good deal more explicit that that [edit: easy]
18 – 59 cm is not much more than what’s expected from thermal expansion, as the report explicitly excluded ALL of the changes in ice dynamics that have been observed since even before the cut-off for inclusion in the report.
Jim, Agreed, and depending on what one thinks will happen with methane and what one thinks the time to equilibrium might be–the answer could actually higher or lower than the ultimate equilibrium temperature.
Looks like a Delphi-type instrument? It should be interesting to see whether the average of everyone’s answers, many of which call for WAG techniques, will resemble model results or something gloomier.
In any event, the $20 donation card I got for filling it out just went to our local animal shelter, which made things oddly more fun.
Usually this kind of survey is validated on a small sample before being given to the target population; perhaps this is still at a validation step?
Using an investment adviser’s website rather than an academic website seems odd since the lead author is a PhD candidate at CMU. Clarifying whether this is an academic poll or a business data collection might help.
Sidd questions the terms, which seem unusual for academic work (can anyone with recent academic experience comment on those?
This seems typical of commercial data collection:
“Vision Prize safeguards your privacy and will never sell your information to a third party.” http://www.visionprize.com/faq
“Notwithstanding the above, in the case where we merge, sell Vision Prize, or otherwise transfer operational control of Vision Prize to a new owner, whether we do so directly or indirectly, you hereby authorize us to transfer all information collected about you …’ http://visionprize.com/privacy Revised: October 10, 2011
hm, anybody able to see this link? It’s apparently using an iframe
“Vision Prize builds on a long history of innovation in scientific opinion polling, and is affiliated with researchers at Carnegie Mellon University.”
Not a bad idea to poll a target audience with some confirmed expertise, but many of the questions are annoyingly imprecise and obtuse, missing opportunities to draw out useful responses.
I notice that it took me, an amateur with no professional qualifications directly related to climate science, only moments to independently identify multiple weaknesses in the questions, the same weaknesses that other commenters have pointed out. So, thanks for the education, RealClimate.
Most people would have no idea of the numerical answers and those who do are likely to find the questions ill posed. I don’t know if Peter Kriss cares about any quantitative answers; it may be some sort of attitude check – and these particular questions don’t do much for mine ;). I’m in the “people who know enough to answer the questions may find them ill posed” group.
2. If policies stay the same when will CO2 get to 550? Since the rate of CO2 increase is itself increasing, sooner than you think, but unknown.
“If policies stay the same” is a defect with the questions, but I’ll take advantage of it. On the one hand, to make any quantitative prediction a specific emissions scenario is needed. Otherwise all we have is an unknown acceleration in the growth of CO2. But I think there is another serious assumption within the “if policies remain the same” questions. To make numeric projections on that basis, one implicitly assumes that only an intentional top-down policy decision can make a difference in Big Carbon’s dreams. Friends, can you think of ways in which that might not be the case?
# 3 and 4. Given a carbon burning free-for-all, who knows what the transient response will be in a particular year? Perhaps an influx of meltwater will bring surface temps down for a year or two.
These questions reinforce the bad idea that the global average surface temperature as such is what we have to worry about.
Edward Greisch @ 12 is right: we need better questions, not just better posed ones.
5. We are on track to be “virtually ice free” (below 1 million km**2) at the end of the melt season sometime before 2020, which is not to say that it happens every year after that.
6. Question refers to a non-existent datum. The conservative estimate now is 1 meter, but with an unimpeded carbondammerung it would be more.
7. Number of “major” hurricanes in a particular decade? beats me. An odd one hit Alaska this fall. For human purposes, let’s think about the word “major”. It should refer to the damage done, not simply wind speed. With increasing atmospheric moisture content (away from arid areas, also increasing) and the increasing tendency to bunched precipitation, mere tropical storms and depressions are ever more dangerous.
9. The most pernicious question. What wonderful economic growth (concentration of wealth) would have to be sacrificed to do anything besides burn carbon burn?
What is the track record of industries crying “it would cost us something” and it turning out to be a benefit to society? How will a massive jobs and research program hurt the economy? And finally,
All those who want to be there when we persist in carbon dependence right up to the day when climate disruption and resource wars stop us, raise your hands.
Comment by Pete Dunkelberg — 24 Jan 2012 @ 3:51 PM
“Most people would have no idea of the numerical answers and those who do are likely to find the questions ill posed. I don’t know if Peter Kriss cares about any quantitative answers; it may be some sort of attitude check – and these particular questions don’t do much for mine ;). I’m in the “people who know enough to answer the questions may find them ill posed” group.”
Exactly, the questions are typical psychology survey questions best answered “yes” “no” “maybe” and “sooner than you think”, especially when they’re headed “give us your best guess.
Is the result of this expected to sway any legislators opinion??
@Dan H, #18:
1. Since 1760 (250 years), the natural effects net pretty close to zero. The total temp rise since then is probably in the 0.9° range, I’m allowing a bit of natural (solar) from then till now.
2. I live on a lake in Minnesota, and I see the ice melt every year. That’s why I find “extent” to be a hugely non-useful metric when discussing ice melt. (It is useful for albedo purposes, but not much else). The fact is, ice melts from below much more rapidly that from the edges. The most relevant metric is volume, not extent. And when you look at the PIOMAS volume data for September, you will find that (a) it’s going down rapidly; and (b) the quadratic fit is much more significant than the linear fit. Do a simple extrapolation and you get 2016-ish. I’m allowing a year for natural variability.
3. Current technology includes nuclear fission, which is more than capable of dealing with global energy needs, and at costs lower than fossil — IF it were only deployed. The barrier is not technological, it’s political.
I guess I missed the 250 years. Must have my mind tuned to 130. I think the temperature has gone up a bit more than that since 1760, but we do not have the data to show it with that amount of precision.
I know many people are touting the PIOMAS data, but the sea ice minimum area is still more than half what it was 30 years ago. In open water, area and volume tend to go hand in hand. Add to that, the melting ice has occurred largely in the warmer part of the ocean. Hence, I did not feel that it would occur before 2050.
While fission could replace current electrical production under the appropriate political scenario, that still leaves heating and transportation needs. Converting everything to electricity with take time and money.
First of all, we very much appreciate all of your feedback.
The poll will be repeated periodically and we will continue to refine and add questions. We do have a feedback forum set up for discussion about the questions and other issues. As for the cases where we need to correct or clarify a question during the poll, we will describe the change on the feedback forum. Before the poll closes we will notify the participants by email of any changes made and remind them that they can revise their answers (which they may do at any time prior to the poll closing).
We are aware that the level of uncertainty may vary dramatically from question to question. Of particular interest to us is understanding the distribution of experts’ beliefs and beliefs about that distribution. We are trying to include questions that are specific enough to be useful to policy makers, vivid enough to be compelling to a broad non-scientific audience (like those suggested by Edward Greisch, 12), and lie within the domain of climate science (as Anteros, 21 points out). We hope to accomplish this, if not within a single question, at least with the breadth of questions.
To address Hank Roberts (27, 29):
Our mission is civic-oriented in that we want to help aggregate and disseminate scientific knowledge in a way that can be used to improve policy. Results of the poll will be published on the Vision Prize web site. Anyone is free to copy, distribute, and transmit the polling data, with attribution. Because this mission extends beyond academic research and could therefore generate intellectual property (e.g. the backend software that runs the site), Vision Prize is structured as an independent research partnership.
That said, because of my Carnegie Mellon affiliation, the involvement of human participants, and the fact that we expect the data to be used in academic research, I am accountable to the Carnegie Mellon Institutional Review Board as a researcher. As such, we have obtained the necessary approval. By “no competing financial interests” we mean that we have no stake in the particular outcome of the research (e.g. we haven’t been hired by Exxon or Greenpeace). The research program is strictly non-partisan and we are not an advocacy organization.
To address sidd (13):
I hope this addresses most of the concerns raised. For all of you that are willing to help us improve the poll, we welcome you to the feedback page. And please feel free to contact me at pkriss AT visionprize.com.
KeithWoollard @ 35, melt contribution from Greenland and Antarctic ice flow has already increased since 2003, moreover, it was already known to have increased before the publication of AR4, which is exactly why the caveats were included. We’ve been through this before. Repeatedly.
If they ask tightly defined questions, they should get the values reported in the literature. Asking less defined questions should give insight into “experts” gut feelings. This one poll may not provide answers, but it may help frame better questions.
“In open water, area and volume tend to go hand in hand.”
Huh? What does that even mean? When both extent and ice thickness are shrinking, how can you ignore the latter? And in considering heat melting Arctic sea ice (whether the heat is advected in, or generated in situ via insolation), is there any reason to conceptualize the process in terms of 2 dimensions rather than 3?
“Add to that, the melting ice has occurred largely in the warmer part of the ocean.”
Well, where else would it occur first?
“Hence, I did not feel that it would occur before 2050.”
This follows how, exactly–? You’re entitled to your feelings, of course, but I struggle to relate your feeling about SIE trajectory to the first two statements in any substantive way.
37 Ray Ladbury: That was un-called-for and off-topic. Cancer more likely comes from benzene and benzene comes from petroleum and coal. Cars cannot have nuclear power plants. Present and past spacecraft sub-critical nuclear batteries produce far too little power. We would never put such a thing in the hands of the public even though we let them have gasoline. Benzene is no longer available at the hardware store. Benzene was available to the public in the 1920s. Now, benzene is released into the air at refineries.
Cars are not climate science.
@Ray Ladbury #37: Believe it or not, electric cars not only are possible, but some are on the road today. Ships can run on nuclear power directly. Heating can be done with heat pumps (electric powered) or direct resistance heating. The only major gap is in air transport, but even there bio jet fuel has been successfully tested. Air amounts to < 20% of the transportation sector in any case.
Are you taking that one graph, and then without taking into account any other scientific research as to why the Arctic sea ice decline is happening, making a linear interpolation of that decline to come up with a “prediction”?
The credible scientific studies I can find indicate that the observed Arctic sea ice decline has accellerated in recent years, which would make a linear interpolation a really lousey estimate with which to predict the future.
#45–Dan, my point wasn’t that 2050 is totally unreasonable. It’s conservative; most modelers, last I heard, were expecting zero sometime in the 2030s, and famously Dr. Maslowski’s model gives 2016 +/- 3, where ‘ice-free’ means less than 1 million km2 at minimum. But it’s not crazy.
My comment was a series of questions about your justifications, which didn’t (and to me, don’t) make sense. OK, I probably got carried away with the leading questions suggesting that *volume* is the significant parameter.
But it very probably is. And you still haven’t addressed that; extrapolation of area obviously still ignores the decreasing ice thickness and hence, volume.
Interesting to note that if you take the PIOMAS numbers and extrapolate them out, you arrive at zero just about when Dr. Maslowski had projected.
Ray @ 44 (No simple solution) – I don’t know about simple, but do do you dismiss Mark Jacobson for example?
Comment by Pete Dunkelberg — 26 Jan 2012 @ 9:33 AM
“In open water, area and volume tend to go hand in hand.”
Check your notes. Look for “multiyear ice”.
Comment by Pete Dunkelberg — 26 Jan 2012 @ 10:12 AM
The sea ice decline (using area) shows a decline somewhere between a linear and quadratic fit (neither fits the data too well). I was using a logarthmic fit, which falls to 1 million km2 in 2050.
There is higher uncertainty in the volume calculations than either the area or extent measurements. In theory, they should show much better correlation.
A few journal articles which put the recent changes in longer term perspectives. One must be careful when using short-term changes to extrapolate longer term effects. This is not to say the the ice is not melting – it certainly has been. However, predictions of rapid acceleration in the next few years are not supported by much of the data.
I responded to Kevin earlier, but it did not post. I was using a logarithmic fit, which results in 1 million km2 in the year 2050. None of the fits; linear, quadratic, or even logarithmic, are particularly good owing to the large variability in the data. Some research suggests that winds and currents play a large role in both variability and overall melting.
There is a big difference between summing up different energy sources and getting the math to close and deploying a working energy infrastructure.
Actually, the problem is probably easier in developing countries where little infrastructure exists than in industrial countries where we must substitute a sustainable infrastructure for a legacy infrastructure.
Then there is the whole problem of transportation–and KAP’s electric golfcarts aren’t going to cut it.
We have a long way to go in terms of energy generation, even further to go in terms of energy transmission and storage, and still further to go in terms of energy sufficiently portable to be viable for transportation. And even once we solve these issues, we have a multi-decade effort for deployment.
And we are pretty much doing bupkes right now to address any of these issues.
Ray Ladbury wrote: “… electric golfcarts aren’t going to cut it …”
Calling the Nissan Leaf or the Chevy Volt an “electric golfcart” is really off the mark.
It reminds me a bit of folks who said that the IBM PC was an overpriced, glorified typewriter/adding machine that would never catch on with businesses.
Speaking of which, IBM is developing lithium-air batteries with dramatically increased energy density compared to today’s batteries, that will give electric cars a range of 500 miles per charge. They expect to have production versions within 10 years.
The continent of Antarctica has been losing more than 100 cubic kilometers (24 cubic miles) of ice per year since 2002.
Measurements from the GRACE satellites confirm that Antarctica is losing mass. Isabella Velicogna of JPL and the University of California, Irvine, uses GRACE data to weigh the Antarctic ice sheet from space. Her work shows that the ice sheet is not only losing mass, but it is losing mass at an accelerating rate. “The important message is that it is not a linear trend. A linear trend means you have the same mass loss every year. The fact that it’s above linear, this is the important idea, that ice loss is increasing with time,” she says. And she points out that it isn’t just the Grace data that show accelerating loss; the radar data do, too. “It isn’t just one type of measurement. It’s a series of independent measurements that are giving the same results, which makes it more robust.”
#51–Appreciate the citations, Dan–though as it happens I’ve read all three previously.
You write “predictions of rapid acceleration in the next few years are not supported by much of the data”–but Maslowski’s date does not require any acceleration, if you trust PIOMAS. (Yes, of course it’s modeled, not measured, and of course there are, as you say “uncertainties.” That doesn’t mean it should be ignored.)
And I think that there is, in fact, some evidence of ‘acceleration’ in this data:
@Hank Roberts #46: Yes, thanks to our advisory group, which includes behavioral researchers, scientists, and science communicators. If you are willing to take the time to give us more feedback but prefer not to use the forum, feel free to email firstname.lastname@example.org.
The PIOMAS volume calculations are a product of the observed area and modeled thickness. Since both the area and thickness are decreasing at approximately the same rate, the volume is decreasing much faster. However, the volumetric decrease will necessarily slow even if the rate of area and thickness loss remain constant (an artifact of multiplying). The volume cannot go to zero before the area and thickness. Therefore, using the PIOMAS plot of volume to estimate a loss of area is invalid.
Your assertion that volume cannot go to zero before extent ignores the fact that we are talking about models here, not reality. In reality, volume is the correct variable to model–and it should yield a less conservative result based on the physics. There is a lot of really crappy first-year ice–that melts pretty quickly. And multi-year ice is getting thinner and thinner. The trend is clearly accelerating–any reasonable analysis of the goodness of fit favors a nonlinear model. I would say that my estimat of 2034 is probably conservative.
Dan H uses any reply to repeat one of the talking points.
He’s a useful guide to which one’s at the top of the list.
So, where’s the push to ignore ice volume coming from these days?
Ray’s point should be obvious — a thin skim of ice can form over a large area, and break up to spread across an even larger extent — yet goes away quickly. Total volume during such a winter will never be much above zero.
Ask the people running the icebreakers which — volume, area, or extent — matters for shipping. Duh.
Based on feedback from participants in the poll, commenters on this post and other members of the scientific community, we have clarified four of the questions in the Vision Prize poll. The new versions have been posted on the site and are reproduced below.
Question 3: If and when CO2 concentration in the atmosphere reaches 550 ppm, what will be the increase in global average surface temperature relative to the year 2000? (Note that this and the next question ask about temperature at a particular moment in time, without reference to whether or not an equilibrium in temperature change has been reached.)
Question 5: When (if ever) will the Arctic Sea become completely free of summer floating ice? (Note that this question asks when the extent of sea ice will be reduced to zero square kilometers, without reference to whether it remains ice free in subsequent months or years.)
Question 6: What is the likelihood that global average sea level will rise more during this century than the highest level given in the 2007 assessment of the Intergovernmental Panel on Climate Change (0.59m)?
Question 10: What decrease (if any) in the annual global economic growth rate percentage would be required to keep CO2 concentration in the atmosphere from exceeding 550 ppm? (Note that this question is phrased in terms of percentage points. For example, a change from 5% to 4% would be a decrease of 1%.)
Updated Information About 225+ Expert Participants
We also invite you to view updated information about our expert participants, many of whom were introduced to the poll by this post. This includes a geographic visualization by affiliation and position and breakdowns by areas of expertise , as well as the public pages of those participants who have elected to share them.
Your interest, feedback and support are much appreciated. Additional participants are welcome.