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« Are judges biased? Or is everyone else? Some conjectures | Main | Scientific dissensus on effect of melting "north pole ice cap"? »

Weekend update: Debate heats up on impact of melting north pole on sea level rise!

Holy smokes!

NOAA has been prevailed upon to reverse its previous position on whether the melting of the  North Pole icecap will affect sea levels!

Until yesterday, the position of the agency, as least as reflected in its "Arctic Theme Page FAQ," was, "No":


Well, after I suggested that anyone of the 14 billion regular readers of this blog who disagreed w/ me that seal levels wouldn't rise should "take it up with NOAA," someone apparently did -- & got the agency to change its view:


But what's the explanation? You won't figure that out from the new FAQ...

It isn't disputed (except by 5 people who wrote me emails...) that a piece of floating ice (an ice cube, say, in a glass of water) displaces a volume of water equal to the volume of liquid water it turns into when melted.

Also it isn't disputed that the North Pole ice cap is simply floating on the arctic sea (although I did hear from a couple of people who said it isn't right to call the "ice cap" on the North Pole an "ice cap"; they should take it up with NOAA too!).

Apparently, though, there is reason to think that "little" is the right answer to the question.

The floating ice at the North Pole is frozen fresh water (not quite but close!), while the body of water in which it sits -- the Arctic Sea -- is salt water.  Salt water and fresh water have different volumes, and apparently this means that less water is displaced by a frozen piece of fresh water than is added to the salt water when that ice melts.

Or so says the source -- a Nature Climate Change blog -- that I'm told was brought to NOAA's attention.

Summarizing an article from Geophysical Res. Letters, the blog states, "[r]etreating Arctic sea ice and thinning ice shelves around Antarctica contribute about 50 micrometers, or half a hairbreadth, to the 3 millimeter or so annual rise in global sea level..."

Presumably the amount contributed by the melting North Pole ice cap is smaller, since the GRL paper states that over 99% of the world's floating ice is in the Antarctic.

But even 1% of 1/2 a hairsbreadth still is something!

Another blogger who noticed this article stated:

Melting sea ice or ice shelves can indeed change sea level. It turns out that I was probably the first person to compute by how much the sea ice can do so, and there's a story for tomorrow about why I wasn't the person to publish this in the scientific literature even though I had the answer more than a decade before the next person to look at the problem.

I'm not sure if that day came-- be interesting to hear the story.

But look: good enough for NOAA & the Geophysical Res. Letters, double good enough for me!  

I have to say though that even if the old NOAA FAQ was poorly worded (as climate scientist Michael Mann stated yesterday on twitter when he kindly responded to my plea for help in sorting through all this) the new NOAA FAQ still strikes me as below the agency's usually stratospheric standards.  

The old answer at least made sense.  The new one doesn't -- b/c it doesn't furnish any explanation for how melting floating ice will raise sea level a "little."

Indeed, the "so" in the new NOAA FAQ--"Ice on the ocean is already floating, so if the North Pole ice cap melts it has little effect"-- strikes me as a true non-sequitur.  

How much the melting fresh-water ice raises sea level depends on how much volume it has relative to the body of salt water it sits in. So if the melting ice in the North Pole will raise sea levels but only a "little" -- as seems to be true-- the explanation is that the volume of floating ice is comparatively small, not that it is "floating," a fact that by itself would imply its melting will have "no effect," just as the the old NOAA answer stated.

If the goal is to help people comprehend, then it is necessary to give them a cogent explanation, not just a "true"/"false" answer for them to memorize.

But hey, I'm really glad that my "climate science literacy" test apparently helped to get this straightened out!  Indeed, I feel smarter now!

Still, I'm worried I might have opened up a can of frozen worms here...

There are lots & lots of additional credible science authorities on-line that draw the distinction the old NOAA FAQ did between the melting sea-ice floating in the Arctic or North Pole region ("no effect-- like a floating ice cube!") and melting ice sitting on land masses at the Antarctic or South Pole region & elsewhere. 



Moreover, the internet is teaming with helpful sources that show middle-school and high-school science teachers how to create an instructive science exercise based on the difference between the floating North Pole ice cap and the land-situated South Pole one:

Indeed, I suspect skilled teaching could explain an interesting feature of the results I obtained when I administered my proto- science-literacy instrument to a national sample.

A full 86% of respondents classified as "true" the statement "Scientists believe that if  the north pole icecap melted as a result of human-caused global warming, global sea levels would rise."

But the 14% that answered "false" clearly had a much better grasp of the nature and consequences of climate change.

E.g., two other true-false items stated:

Climate scientists believe that human-caused global warming will increase the risk of skin cancer in human beings;


Climate scientists believe that the increase of atmospheric carbon dioxide associated with the burning of fossil fuels will reduce photosynthesis by plants.

On each question, over 2/3 of the respondents got the wrong answer.  

That's not good.

It suggests that most of the 75% of the respondents who correctly selected "CO2" as the gas scientists believe increases global temperatures still don't really know very much about climate change.

If they did, they wouldn't think that "skin cancer" will increase. That's suggestive of the long-standing confusion that a hole in the ozone is causing climate change.

Also, if they really got that CO2 is causing climate change b/c it is a "greenhouse" gas, they wouldn't believe that climate change is going to starve the plants that live in greenhouses....

But here is the critical point: if a study participant answered "true" to "North Pole" -- that is, if that person indicated he or she thinks climate scientists believe that a melting North Pole ice cap will raise sea levels--then there was a 67% chance he or she would get both the "skin cancer" and "photosynthesis" items wrong!

In contrast, there was less than a 25% chance that someone who answered "false" to North Pole would answer those questions incorrectly.

It might be the "wrong" answer, but actually, "false" in response to "North Pole" is a better predictor of whether someone is likely to show comprehension of other fundamental facts about climate change.

And in fact, that is what a test item on an instrument like this is supposed to do.

The function of a good science-comprehension instrument isn't just to certify that someone has absorbed or memorized the "right" responses to a discrete set of questoins.

It is to measure a latent (i.e., not directly observable) quality of the test-taker -- her possession of the dispositions and skills that contribute to acquiring additional knowledge and giving it proper effect.

The proto- climate-literacy instrument in fact measures that capacity more accurately when one scores "false" as the "correct" response!

Actually, maybe "false" is the right answer to "North Pole"? Perhaps, as the NOAA FAQ prior to yesterday, and all the myriad other science sources on-line reflect, most "climate scientists" do "believe" mistakenly that a melting North Pole won't raise sea levels?

No idea!

For sure, though, I'd revise this item in refining and improving this proto- climate-literacy instrument.

But one last point: in relation to my purpose in constructing the instrument, none of this matters!

My goal was to test they hypothesis that survey items that ask respondents whether they "believe in" human-caused climate change don't actually measure what they know'; instead they measure who they are as members of competing cultural groups for whom positions on this issue have become badges of membership & loyalty.

Using techniques that have proven effective in determining whether "belief in evolution" measures science comprehension (it doesn't), I devised climate-literacy items designed to disentangle indications of knowledge from expressions of identity.

The results suggested that there is indeed no relationship between what people say they "believe" about human-caused climate change and what they know about climate science.

Because there is clearly no meaningful relationship between getting the "right" or "wrong" answers on the proto- climate-science literacy test and either people's cultural identities or their beliefs about climate change, it doesn't matter which answer one treats and which as wrong in that respect. That is, there is still no relationship.

To me, that's really really good news.  

It means that the ugly, mindless illiberal status competition associated with competing positions on "belief" in human-caused climate change doesn't impel people to form polarized understandings of what science knows.

However confusing it might be to figure out what "scientists believe" about the impact of a melting North Pole on sea levels, people-- of all cultural & political outlooks -- have already gotten the memo that climate scientists believe human-caused climate change is creating a series of challenges that need to be addressed through collective action.

Now it is time for those who are trying to promote constructive public engagement with climate science to get the memo that disentangling climate science from culturally assaultive forms of political action is the single most important objective they all confront.

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Reader Comments (6)

As one of the first people to get this "wrong", I must admit that the business about fresh water never occurred to me. Rather, something else never occurred to me, which was that the "polar ice cap" is all floating. If the question had pointed that out by saying "polar ice cap (the ice that floats in the Arctic Ocean)", I might have gotten it "right" in the sense of knowing that it would not increase the water level by melting. It still bothers me a little that there isn't ANY land at all under that cap, and it doesn't include Greenland or even Minnesota.

June 28, 2014 | Unregistered Commenterjon baron

Dan, don't you feel some Schadenfreude toward people like that commenter who suggested

"Dan Kahan - "But they also incorrectly think that "climate scientists believe" that the melting of the North Pole ice cap will cause flooding."

You can't blame the survey participants for being confused when you yourself are confused about this topic. An icecap is a mass of ice, below a defined surface area size, that sits atop land."

in the other post, i.e. who called you confused and got absolutely all of it wrong himself?

June 29, 2014 | Unregistered CommenterMartin


People who live in glass houses should be careful not to heft Schandenfreude around!

I assume that individual had a legitimate point in mind. I didn't myself come up w/ this question -- as I indicated, it is one featured in "climate literacy" materials on various sites -- so I didn't think the "ice cap" point was particularly important.

But I myself hadn't seen the materials that say, "wait a minute, everybody! Not so fast on that melting North Pole ice cap!" So I don't think I have standing to say he was any more confused than I was.

Indeed, I admire the individual who decided to contact NOAA to complain about its FAQ! He or she has a lot of work to do, though -- that was just the "tip of the iceberg" on this one (even NOAA didn't really make things any clearer for visitors to its site -- too bad).

I suspect @JB would agree with me that "letting the test takers" settle the matter -- that is, seeing which answer cohered better with the latent "climate science comprehension" dispositoion.

But as I said, I would definitely revise the item if I were to continue working on such an instrument.

A more interesting question is whether the item, when worded to avoid confoudning the off-the-scale peope who already knew that the melting north pole could increse sea level 1% of 1/2 a hairsbreadth, should be retained.

Chris Mooney called it a trick question.

I don't agree! it does in fact tempt people who assume the North Pole ice cap is part of what is being discussed when climate scientits link flooding to melting polar ice. But that is the mark of a *good* test question: the wrong answer seems right except to those who actually know the answer.

The reason not to regard the question as very interesting is that it arguably insn't the sort of "climate science comprehension" that very many people need. As In dicated in an earlier post, if they know that sea levels are rising b/c of melting polar ice -- that's good enough for them to participate intellignently in democratic deliberations.

But there are high school students & others...

It is surely a mistake to think there can be a 1-size fits all "climate literacy" assessment or any other kind of "science comprehension" assessment for that matter!

June 29, 2014 | Unregistered Commenterdmk38

@ dmk38

Yes, taking seriously such remarks, even if they are brought up in such a snotty fashion, is certainly a winning position. My question was only half-serious and on style rather than on content: namely exactly the fact that the commenter didn't see any clearer, and most of all did not seem to understand the point of the exercise - but, or therefore, had the chutzpah to assume you are confused. No suggestion, no question, not even the conclusion of a critique, but the announcement from the get-go: 'You are confused, because for sure I am not!'

June 29, 2014 | Unregistered CommenterMartin


I see what you are saying. But as you know, some amount of that is just built into internet comments; it would reflect self-importance to take it personally!

So I don't care enough to take satisfaction when someone is shown wrong (& have little reason to believe such a person will notice).

I do worry, though, that being exposed to such comments -- and as a result coming to expect them -- will cause me to misconstrue some fraction of the commenters' intentions & either react negatively to or (more likely) ignore comments that reflect reasonable disagreements, questions, or confusion. I'm sure this is happened now & again, sadly.

In the case you are remembering, I recall responding to point out only that I didn't think people who got that wrong were ill-informed -- I think they have nothing at all to worry about unless they are in one of the apparently large number of middle school classes that use the "North Pole model vs. South Pole Model" exercise to teach about climate & about the physics of frozen water displacement/volume!

June 30, 2014 | Registered CommenterDan Kahan

It's a general problem. As I've been saying, these sorts of subtleties and ambiguities apply to most of the questions asked in these surveys. (Like when you say "Is global warming happening?" do you mean is it happening now, or over the past 15 years, or over the past 50? It matters.) So you get a mixture of two effects - the degree to which people disagree on the answer, and the degree to which they disagree on the interpretation of the question. You can get systematic variations in both.

I did think about mentioning the ambiguity myself. I was aware of the Greenland issue (and even the salinity issue, although I'd have dismissed that), but I was also considering the possibility that some people might have known the correct answer but be under the impression - what with all the media stories about Arctic melting linked to flooding - that 'consensus' scientists thought differently. After all, if they can believe in global warming catastrophe, then why can't they believe that floating ice melting will raise the water level?

However, it seemed a minor nit-pick, and only repeated what I'd already been saying at much greater length about all the other survey questions in the "97%" surveys. We haven't even got to the point of being able to ask the right questions.

However, since you've apparently got a route in to get NOAA pages corrected, perhaps you can prod them about the one that says "The atmosphere acts like the glass in a greenhouse, allowing much of the shortwave solar radiation to travel through unimpeded, but trapping a lot of the longwave heat energy trying to escape back to space", which has been bugging me for years. ( The atmosphere does not act like the glass in a greenhouse, and not even actual greenhouses work that way (as they correctly say here, although they still manage to get the GHE wrong).

Moreover, if the greenhouse effect really worked by that mechanism, the oceans would explode! (Liquid water lets visible energy from sunlight in but blocks IR from escaping too. Water internally emits a huge amount of back-radiation downwards, which if you believe the internet explanation ought to 'greenhouse' it up to a temperature of several thousand degrees.)

In fact, if you could get them to fix all the thousands of pages around the world that incorrectly explain how the greenhouse effect works, that would be brilliant!

I can only hope your stunning success with NOAA here wasn't just a fluke... :-)

June 30, 2014 | Unregistered CommenterNiV

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