Bishop Hill Inside mathematics
Jan 10, 2014 BBC Climate: Surface The BBC's Inside Science programme looked at the Ship of Fools expedition yesterday. We were treated to the unedifying sound of presenter wondering about whether what he called "deniers'" views on sea ice extent in the Southern Hemisphere carried any weight. We were led to beleive that they did not. Normal BBC fare I hear you say.
Some of what was said was bizarre though. Interviewee Professor John Turner of the British Antarctic Survey said the rise in Antarctic sea ice extent was less than 1% and was therefore well within the bounds of natural variability. I have no problem with the second part of that statement, but 1% seemed very low to me. Here is the relevant graph from the Cryosphere Today website.
The Antactic sea ice has an annual mean of 9 million km2 or so and the current anomaly is 1.395. So we are at 14 or 15% above normal, not less than 1%. Am I missing something, or does Prof Turner have a problem with his mathematics?
The audio is attached below.
Bishop Hill
Prof Turner emails:
Based on the Bootstrap version 2 passive microwave sea ice data the annual mean Southern Hemisphere sea ice extent increased at a rate of 147 × 10**3 km**2 per decade (1.2% per decade) over 1979-2011, which is significant at p<0.01.
I think that's him agreeing that the figure he gave on the BBC was wrong, but I've emailed back asking for clarification. Remember folks, there is nothing wrong with errors if they are corrected.
Bishop Hill
The British Antarctic Survey Twitter account just pointed me to this paper.
@etzpcm Here is a paper you might find useful with 1% per decade fig: http://t.co/q4E0lcUJh2. Thanks to you and @aDissentient for contact.
— BAS_News (@BAS_News) January 10, 2014
I'll see if I can get a copy, but the tweet makes it clear that when Prof Turner said there had only been a 1% increase in sea ice, he meant 1% per decade. Moreover, the paper was submitted to the journal in January 2009 and was published a few months later. It is therefore unlikely that it includes data beyond 2007.
Here's the longer term record of the Antarctic sea ice anomaly:
As you can see, things have moved on quite a bit since that time. That said, his original email said 1.2% up to 2011, so I'm still not entirely clear.
Bishop Hill
Another email from Prof Turner
- the trend was calculated from the annual mean total Southern Hemisphere sea ice extent.
- the percentage increase was based on the average annual SIE for 1979-2011 since there is no reliable whole Antarctic sea ice data before 1979.
If you include the 2012 data the trend increases to 157 × 10**3 km**2 per decade (1.27% per decade).
2012 didn't have the largest annual mean in the record, but it did have the largest daily ice extent, which occurred on 24 September. Our paper on this event is attached. In 2013 there was an even greater extent of Antarctic sea ice in September, so many people are trying to understand the mechanism or mechanisms responsible for the changes we are seeing.
Reader Comments (119)
The ice is melting. A scientist said so and you just can't argue with facts like that. :-)
"In 2013 there was an even greater extent of Antarctic sea ice in September, so many people are trying to understand the mechanism or mechanisms responsible for the changes we are seeing."
Freezing?
@Billy Liar No I don't think he is saying that rate of change is increasing by less than 1%
But he is trying to say "up, yeh by less than 1%", but he must know ice levels are well up on 1979. It's difficult to put a % number on it cos in winter it peaks near 16m sqm and summer dips to just above 2.5m sqm. It used to be between 15 and below 2 so I wouldn't pass it off as only 1% change
check figs on wattsupwiththat.com/reference-pages/sea-ice-page
..
and I should correct myself Chris Turner does talk about "sea ice" not all Antarctic ice
bet Turner and Rutherford are mates so possible concoction.
- strange how BBC got rid of the unalarmist Material World and replaced it with a prog headed by Rutherford who like Turner studied under Steve Jones.
..more like DistortingScience ... you b'ards
btw - Bish:
"Update on Jan 10, 2014 by Registered CommenterBishop Hill
Another email from Prof Turney"
Prof Turner?
François-Marie Arouet (Voltaire)
"I disapprove of what you say, but I will defend to the death your right to say it"
Although this quotation is often misattributed to Voltaire, I am certain that he would
have been proud of it (had he espoused it)
I think that it would be a good idea if those who take part in broadcasts such as the
one we are discussing; were asked (prior to any discussion;whether or not they subscribed
to this sentiment.
Their answers just might encourage a more circumspect consideration of those whom might
beg to differ.
Off topic
Voltaire's mistress(Émilie du Châtelet) was a least, Voltaires pear, studied and contributed to
the science of energy and energy conservation. She was a truly remarkable lady.
The latest update email from Prof Turner makes it quite clear that the figures used in the programme were highly misleading. 1.2% per decade for more than 3 decades compounds to a jolly sight more than 1%. A journalist might be excused that sort of error, but an expert?
There is also a lot of difference in area between 1% of arctic sea ice, and 1% of antarctic sea ice, again, no qualification of that in the programme.
He also failed to mention the recent uptick, and large extents seen, which from his emails it's quite clear he knew about, prefering to stick with a figure for decadal increase which is out of date.
That lot I think makes the whole piece a cynical exercise in manipulation, and he should be ashamed of himself.
I have complained. Antarctic Sea Ice data here
Sandy S
Could you unpack that data a little. Column headings would be useful.
not banned yet
"Freezing"
Obviously. But is it due to lower temperatures, lower salinity, more intense storms, more meridional winds or some combination?
Antarctic temperatures are static. Salinity is decreasing. Storms are intensifying and winds are becoming more meridional.Take your pick.
http://nsidc.org/data/seaice_index/
I would suspect that the % increase per decade is based on the slope of the linear regression of the data since the Antarctic sea ice extent was first measured by satellite in the early 80s.
The graph I've linked shows 2.1% +/- 2.0% per decade to December 2013.
Revered Bishop: Don't you mean 'Prof Turner'?
Of course, I've seen so many spellings of silly ice wandering Turnbuckle, er Turnoff, er Turnback, whatever, recently! I've gotten a bit jaded, still don't you mean the Prof in the interview?
Entropic man (12:30 AM): "Column headings would be useful."
I agree. I'm not familiar with this file, but it appears that:
1st column is year (including fractions)
2nd column is sea ice area anomaly (in units of 10^6 km^2)
3rd column is actual sea ice area (10^6 km^2)
4th column is the baseline area, for the period 1979-2008 (10^6 km^2)
Turney is rumoured to be working on a cover version of the Stealers Wheel hit ‘Stuck in the middle with you’
“Clowns to the left of me, jokers to the right,
Here I am, stuck in the middle with you.”
http://www.youtube.com/watch?v=5ukstws19D4
CYNICAL !
1979 to 2012 that's 33 years=3.3 decades
at 1.27%*3.3 =4.191%
so by his own figures he's out by a magnitude of more than 4 fold
(and I would expect that 1.27% is a a result of gerrymandering to the lowest possible. I wonder what credible figures other people get ?)
- right from the beginning he is cynically downplaying ice-growth
and Adam Rutherford is either playing along or too badly informed to be a presenter on this matter.
... Don't worrry Adam in the next 33 years we'll only be reducing your pension pot by 1% .. sorry 1%/year... but that's practically the same thing isn't it ?)
- Quick clear apology and corrections wouldshow CREDIBILITY : but no contrition from Turner. He & Rutherford seem to live in an alternate green universe
Re: stewgreen
You are in error with your calculation. It is a trend so it should be compounded. The correct equation is:
1.0127 ^ 3.3 = 1.0425 = 4.25%
But even then, within the context of the interview, they are talking about the sea ice at that time of year (December) which is 2.1% so using this gives a percentage increase of 7.1%
TerryS
7% since 1981 for December sounds about right.
http://nsidc.org/data/seaice_index/
Click Antarctic here and you'll see about a 7% rise for December since 1981. The really interesting thing is that the high values have all been since 2006.
If you start counting from the step change that's 1% per year!
Old Nimbus data allowed a reconstruction of the September 1964 Antarctic extent at 19.7 million sq. Km.
http://nsidc.org/monthlyhighlights/2013/04/glimpses-of-sea-ice-past/
September 2013 was 19.47.
EM
I haven't looked at the paper, but I can quite believe it. I think natural variability is probably much higher than mainstream science suspects.
Entropic man -
Not that it matters to your point, which is well taken, but at 1:59 you give the September 2013 Antarctic sea ice extent as 19.47 million sq km. However, in this file, I see 19.77. Is the "19.47" just a typo, or are you reading that from another file on the site which I should be looking at? The reason I ask is that I'm trying to understand how the monthly data (in the above file) corresponds to the daily values in this file. If there's another monthly figure which they produce, it might help my effort.
Can we assume then EM that you agree that the R4 interview by Turner was very misleading?
Not exactly straight talking. Strange obtuse talk from Turner as if he is trying to spin a story Why the heck is he denying something that no one has ever mentioned ie, that human activity is cooling the Antarctic ? "But in the Antarctic, this small increase, I think, is so small we can't really say it's caused by human activity - it seems to be within the bounds of natural variability of the Earth system. "
plus
"And a 1% increase, I believe, is within the bounds of natural variability. So we can't really infer global change from a measurement like that."
.. again strange.. why would anyone say you can imply GLOBAL change from any one localised change ?
@TerryS thanks yes a small error by me I forgot to compound it, but I was in the same ballpark , whereas Turner is kilometres away.
from adamRutherfords twitter profile "Tells stories, makes stuff"
"tells stories" is that a Freudian slip ?
is "up" missing from the end ?
Jan 11, 2014 at 4:30 PM | Cumbrian Lad
Good question! The hard ones always frighten ectopic man off.
You can run the same Cryosphere figures for tyhe North Pole.
The annual mean looks about 10 million sq km, and the latest anomaly is -0.980.
This is a much smaller decline than the Antarctic increase.
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.arctic.png
Harold W
I got the September 2013 figure here.
http://m.earthobservatory.nasa.gov/IOTD/view.php?id=82160
I wonder if the author got the daily and monthly averages mixed up?
Cumbrian Lad
You are getting het up about fractions of a % when the uncertainty in the measurement is +/- 2%.
What would be misleading would be any suggestion that the Antarctic Winter sea ice is changing significantly at all.
I'm rather amused by the way spin-sceptic sites like this push two contradictory memes.
1) A 2%/decade increase in maximum Antarctic extent indicates that the Antarctic is cooling.
2) A 13.7%/decade decrease in minimum Arctic extent does not indicate that the Arctic is warming.
Billy Liar
Why do you want to frighten me off?
Bishop Hill
Since we have full extent data from 1964 and from 1979 on, it is quite possible that there is more variability than we've observed. The Holocene optimum may well have had smaller extents and the LIA larger ones. Glacial period extents would probably be a lot bigger.There is research under way to use sediment and biological proxies to deduce past extents. For the moment all we can do is follow Newton's 4th principle of inquiry and use the data we have.
What we don't have for the years with data is significant change.
Apart from the West Antarctic peninsula, which is warming, the high Antarctic is insulated by latitude and the Southern Ocean. I doubt that even the more pessimistic scientists studying the Antarctic expect much change for a good while yet. Even if we do see change, separating climatic and ozone hole effects will be fun.:-(
Stop wriggling EM. Very straightforward issue. In public, on the radio, John Turner said that sea ice had increased by 1%. No qualification. No wittering about uncertainty limits. You agree that the figures show that the increase has been more than that. He also neglected to acknowledge that the increase has been greater in the recent past, an increase not included in the figure he gave.
Do you, or do you not agree that that is misleading?
Cambrian lad
When you do a radio interview do you talk as though you are in a seminar?
The level of detail you demand is more appropriate for a conference or paper, not for a programme aimed at the intelligent layman. He made the key points. The change was small and probably natural.
When I do a radio interview (and I've done many) I aim to get across accurate information and importantly give the correct t impression. Moreover I don't patronise my audience by assuming they will not understand any nuance. The facts here are clear EM. The listeners to that broadcast were mislead, by more or less any criterion one fairly applies. The more you avoid admitting that, the less respect I have for you.
I would add that audiences in general are capable of understanding surprisingly complex concepts if you allow them to. I have given seminars to scientists as well as talks to less technical audiences and it may surprise you but the lay audiences often have the most interesting questions. Even in it's best science programming the BBC can be very patronising. I suspect that one of the things that worries politicians and scientists trying to control the climate discussion is the growing realisation that the man on the clapham omnibus ain't as daft as they thought he was.
EM - "Antarctic temperatures are static. Salinity is decreasing. Storms are intensifying and winds are becoming more meridional.Take your pick."
Give me the data set references that your assertions are based on, along with their error bounds and the periods they cover, and I might have something to go on. As an additional request, do you have anything on sea temperatures or cloud cover?
not banned yet
The student should really be doing his own homework, but here are a few references.
Temperature wise the coastal records are a hodgepodge, some rising and some falling.
http://notalotofpeopleknowthat.wordpress.com/2013/11/08/antarctic-temperature-trends/
Sea surface temperatures also vary with location, some up and some down.
http://www.hindawi.com/isrn/oceanography/2013/392632/
Salinity trend, due mainly to ice melt off the land. (see GRACE and CRYOSAT data.)
http://journals.ametsoc.org/doi/abs/10.1175/2010JCLI3284.1
Wind changes and cloud
http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00139.1
Those are from a quick Google search.
You'll also find discussion of the same processes at NSIDC.
http://nsidc.org/icelights/2012/01/11/sea-ice-down-under-antarctic-ice-and-climate/
The problem is multifoldfold.
The changes in extent are much smaller than in the Arctic, barely showing above the noise of short term variation. Because of this, one cannot even be sure that there is a trend to study.
The Antarctic is a continent surrounded by ice and water. There are a lot of interactions between the three, which makes it difficult to assign causes and effects. The consensus among those studying Antarctic ice extent is that wind is probably the main influence. Add the ozone hole and it becomes well nigh impossible. There's also the problem that sea ice may be increasing, while ice shelves are tending to break up (see Larsen B)
Personally I'm not surprised that the only area which shows consistent warming is the West Antarctic peninsula, which sticks out into the Southern Ocean.
http://www.antarctica.ac.uk/bas_research/science/climate/antarctic_peninsula.php
The rest of the continent is insulated from the climate system by the circulation in and over the Southern Ocean, by latitude and, in the interior, by altitude. It is, in the most literal sense, the last place you would expect to see climate change.
Cambrian Lad
A 5-10 minute interview gives you time for perhaps 500 words. I think he pitched it about right.
Perhaps you could put forward a sample script for Professor Turner's interview including all the complexity you feel he missed out.
Entropic man (7:46 PM)
Thanks for the reply. I read that press release as saying that the Sept 22 extent was 19.47 million sq km, and set a new daily record (over the satellite era). This value matched the figure for that date in the daily files, given as 19.4683.
By the way, the extent crept up a little higher, setting new records: the Oct 1 extent was 19.57.
You are evading the question again EM.
EM -
What problem? That a continent with an average temperature at the coast of -10C and an average in the interior of about -50C has maybe or maybe not 'warmed' by a fraction of 1 degree in the last 30 years? That there is no evidence to show that this alleged rise is due to CO2 and not just natural variation? The only warming in the interior came about after a good dose of Mannian statistics a la Steig et al 09, a paper which in any other discipline would have been withdrawn. Meanwhile the expansion of the sea-ice is making a nonsense of the climate models.
The fact is that Professor Turner's 1% statistic was unqualified and misleading. Stop trying to make excuses for him.
btw there is already very good paleo and geological and archeological evidence for the Arctic sea ice to have been much smaller in extent during the Holocene Optima - raised beaches, driftwood and human camps on the north coast of Greenland. And the Arctic Ice sheet was much larger during the glacial periods, e.g. an erratic on Tiree which came from Rum.
EM - "The student should really be doing his own homework, but here are a few references.....Those are from a quick Google search."
Yep - driving google is the easy bit isn't it EM? How about you actually answer the question put:
What are the data sets, the periods of time they cover and the error bounds on the numbers?
Lapogus
On sea level we agree about the variations due to glacial periods. Be careful when interpreting beaches. 40 miles from my home is a raised beach 5m above current sea level. It formed after the local ice sheet melted 10,000 years ago when sea level was lower and was then raised by isostatic uplift.
"Not just natural variation"
Natural variation is not just randomness, it is cause-and-effect mechanisms in action.
Knock-on effects of increasing CO2 provide a sufficient mechanism for most of the scientists.
What mechanisms do you invoke to explain the changes,and on what evidence?
Cambrian lad
For an academic you are remarkably obtuse.
I do not regard Professor Turner's interview as misleading.
Read the abstract of his 2009 paper.
http://onlinelibrary.wiley.com/doi/10.1029/2009GL037524/full
I quote from the abstract.
"Based on a new analysis of passive microwave satellite data, we demonstrate that the annual mean extent of Antarctic sea ice has increased at a statistically significant rate of 0.97% dec−1 since the late 1970s."
As an active scientist publishing in the field, I am more inclined to accept his word than yours.
Not banned yet
Somehow, whatever side of a discussion I'm on here, I'm expected to do the legwork for both sides
If you wish to present a view differing from the consensus do your own damn legwork.
EM
An increase of 0.097% per decade since the late 1970s is not 1%; it's 3%.
Turner's statement was inaccurate, misleading, and quite likely deliberately so.
I'm not really sure whether the figure is "significant" in anything other than a statistical sense but what we conclude from this episode (as we have concluded time and again over the years) is that climate "scientists" are more than happy to play fast and loose with figures if it gives them an "edge".
It's stupid, unnecessary, and will one day come back to haunt them. I fervently hope.
Ignoring the ad hom, (and the third miss-spelling of my nom-de-plume; do study some geography there's a good lad) we eventually have his answer:
"I do not regard Professor Turner's interview as misleading."
John Turner's own paper says that the ice has been increasing in a statistically significant way - so that blows EM's earlier excuses out of the window. And as Mike J's paragraphs concludes, the ice has increased by more than 1% and that's before the recent uptick in ice growth.
Well, you've nailed your colours to that particular mast EM.
I'll pass over the ugly appeal to authority at the end of his contribution.
Mike Jackson
Go to the top of this thread and read each of Professor Turner's statements. Read the abstract I referred you to. He, and the rest of us outside your blinkered little world, work with per decade rates as a matter of course.
Hence we talk about an increase of 1.3% to 2013 for the Antarctic and a reduction of 13.7% for the Arctic.
If you really prefer we can talk of a 4.42% increase since 1979 and a 46.6% decrease.
You now have the problem of explaining why you are getting excited by the 4.42% mote while ignoring the 46.6% beam.
Cumbrian lad
As far as I'm concerned you're just some bloke on a blog, as I am. When you demonstrate the same professional qualifications in this field as Professor Turner I will give your opinion the same respect I give his.
The "appeal to authority" debating argument is only spurious when the authority is spurious. If the authority is legitimate, so is the argument.
Just for fun, I notice that Arctic ice extent for yesterday is about 2.4% below the value for that date in 2012.
http://nsidc.org/data/seaice_index/images/daily_images/N_stddev_timeseries.png
By your standards, gentlemen, this is clearly worthy of note. I trust you will acknowledge that the "recovery" since the Summer of 2012 has reversed. ;-)
You'll need to do your homework better than that EM. Argumentum ad vercundiam is a lot more sophisticated than that, and in fact you breached it in two respects.
I have my answer from you, thank you, and will leave you to the tender mercies of the facts.
Cumbrian lad
The facts support cAGW.
Cumbrian lad
To paraphrase Robert Bolt; threaten me with facts and I am not threatened.
Why did "scientist" Prof Chris Turner spend time answering a question that no one asked ? "the growth in Antarctic ice is less than 1% well within the natural variability" ?
.
Well scenario 1 - Prof(essional climate activist) Chris Turner has an opportunity to get his PR message across on radio which is "Oh my God ! look at the Artic Ice melting, look what man has caused with Climate Change" So he needs to head off another idea at the pass : "Yes Artic Ice did drastically decline, until it mostly recovered in 2013 and anyway isn't Artic loss balanced by Antarctic gain ?
He needs to get across "No, that Antarctic gain is just natural variability"
... so before anyone asks that question he gets his cover message in
- No skeptic is saying Antarctic Gain is made by man, cos they are saying the Artic loss is within natural variability, if there really is such a thing (and that Earth's phenomenom don't vary all the time extensively), so of course Antarctic is with "natural variability"
.. that plausible ? cake & eat it ?
Artic loss= CAGW proof, Antarctic Gain= natural variability