AR5: cursory review of chapter 4 (cryosphere) mass balance of Antarctica

The AR5 draft is now available from http://www.climatechange2013.org/report/review-drafts/. W00t! In the style we’ve come to love so much from the IPCC it sayeth:

The final draft Report, dated 7 June 2013, of the Working Group I contribution to the IPCC 5th Assessment Report “Climate Change 2013: The Physical Science Basis” was accepted but not approved in detail by the 12th Session of Working Group I and the 36th Session of the IPCC on 26 September 2013 in Stockholm, Sweden. It consists of the full scientific and technical assessment undertaken by Working Group I. The Report has to be read in conjunction with the document entitled “Climate Change 2013: The Physical Science Basis. Working Group I Contribution to the IPCC 5th Assessment Report – Changes to the underlying Scientific/Technical Assessment” to ensure consistency with the approved Summary for Policymakers (IPCC-XXVI/Doc.4) and presented to the Panel at its 36th Session. This document lists the changes necessary to ensure consistency between the full Report and the Summary for Policymakers, which was approved line-by-line by Working Group I and accepted by the Panel at the above mentioned Sessions.

(My bold). So that’s a pain up the f*ck*ng arse then – anything I want to read I have to first check they haven’t revised? Spare me. Note, though, that the revisions seem to be of the sort Trickleback Figure 4.4 The trends numbers need to be removed to avoid the excessive significant figures, and ensure compatibility with numbers provided for SPM, which are given for different likelihood statement. The uncertainties are likely not very likely, so is confusing! Joey Comiso to provide revised figure, with trends given to match numbers in the SPM – i.e. the tedious process of aligning stuff, so I doubt I have to care very much.

Oh, but before I leave off insulting them: what kind of idiot puts up a document of such obvious public interest and then writes on it “Do Not Cite, Quote or Distribute”? Will someone please fire the IPCC press office and get them someone competent.

I decided to read Chapter 4 (obs; cryosphere) and specifically the Antarctic stuff. And specifically the mass balance of Antarctica, since I used to know about that a bit. So I’m looking for the text supporting:

The Antarctic Ice Sheet has been losing ice during the last two decades (high confidence). There is very high confidence that these losses are mainly from the northern Antarctic Peninsula and the Amundsen Sea sector of West Antarctica, and high confidence that they result from the acceleration of outlet glaciers. [4.4.2, 4.4.3, Figures 4.14, 4.16, 4.17]

That’s interesting to me, because when I started (and arguably when I stopped, around 2007) the overall mass balance of Antarctica was unknown, including its sign. That’s because in general you were trying to difference two large numbers (accumulation at the top, against loss form the edges) and the uncertainties in either were bigger than the difference. For comparison, AR4 said:

Taken together, the ice sheets in Greenland and Antarctica have very likely been contributing to sea level rise over 1993 to 2003… Estimates for the overall mass balance of the Antarctic Ice Sheet range from +100 to –200 Gt yr–1 (–0.28 to 0.55 mm yr–1 SLE) for 1961 to 2003, and from +50 to –200 Gt yr–1 (–0.14 to 0.55 mm yr–1 SLE) for 1993 to 2003. The recent changes in ice flow are likely to be sufficient to explain much or all of the estimated antarctic mass imbalance…

So what has changed? Well page 4-28 says:

Since AR4, satellite, airborne and in situ observations have greatly improved our ability to identify and quantify change in the vast polar ice sheets of Antarctica and Greenland. As a direct consequence, our understanding of the underlying drivers of ice-sheet change is also much improved

Hmm, OK. But in detail? There are three methods: mass balance, altimetry, and GRACE (I last wrote about GRACE in 2009 I think). “The mass budget method (see Glossary) relies on estimating the difference between net surface balance over the ice sheet (input) and perimeter ice discharge flux (output)”. They discuss the net sfc mass balance, and provide numbers. Oddly, they don’t provide any numbers for the discharge side. Also, if you look at Table 4.A.3 “Sources used for calculation of ice loss from Antarctica” you’ll find that they’ve used GRACE overwhelmingly.Aside from which there are two others: they also used “Shi et al., 2011” but as they say “Methodology and error budget incompletely described” and also it arrives at an uncertainty of 5 Gt/yr, which is implausibly precise, so forget that. And they used Rignot et al. 2011c. That uses the std-ish long trail of stuff (ice velocities, corrections for grounding line movement, etc. etc.) to get you as far as ice discharge rates. And that leaves you with an overall value that makes the mass balance negative. I’d be slightly iffy about whether the values are really known closely enough, but the point (in Rignot too, since they use it) is that it agree with GRACE, so So There we’ve got close enough and can stop now.

But overall, it looks pretty clear that the main advance has come from using GRACE. Which is really funky and fairly direct, so good. Note, BTW, that although I’ve been somewhat sniffy in my I-used-to-know-this-stuff way about the absolute value of the contribution from Antarctica, this isn’t desperately important – what matters is the change over time, and everyone agrees (now, unlike AR4) that this is leading to SLR.

Refs

* Victor Venema at “Variable Variability” is collecting other (generally more temperate) reviews of AR5.
* A Reconciled Estimate of Ice-Sheet Mass Balance

AR5 follow on – weirdness from la Curry

Judith Curry has a weird post called “IPCC diagnosis – permanent paradigm paralysis” which starts off with a perfect example of the denialists favourite tactic – a walled garden of links to their own nonsense. She says:

In a previous post, I discussed the IPCC’s diagnosis of a planetary fever and their prescription for planet Earth…

Now if you’re a person prepared to believe that JC isn’t lying through her teeth, you might actually not follow that link, and in consequence you might believe that what she said was true. But it isn’t; its a fantasy as wacky as AW’s about wikipedia. If you actually read the article of here’s that she links to you find that its a mixture of The Onion, and Romm. There is no IPCC diagnosis in there at all; and no IPCC prescription.

She continues the fantasy-land stuff with as temperatures have declined and climate models have failed to predict this decline, the IPCC has gained confidence in catastrophic warming and I gave up at that point. Curry jumped the shark back in 2010 but this is a whole new level. She’s lost touch with reality and is wandering lost inside the denialosphere with no compass and no keel and no bottom.

Refs

* Curry repeats her drivel in the financialpost

What they said

So, AR5 SPM is out. The obvious place to start is RealClimate or perhaps you could even read the SPM itself. Here’s a quote:

Each of the last three decades has been successively warmer at the Earth’s surface than any
preceding decade since 1850 (see Figure SPM.1). In the Northern Hemisphere, 1983–2012 was
likely the warmest 30-year period of the last 1400 years (medium confidence)

And there’s even some nice pictures; here’s one of them:

But enough of this insightful but tediously detailed analysis, I hear you say, what about the reactions? (Actually I hope to read the thing properly sometime and maybe even comment on the bits I understand).

The MSM seems to be “on message”, for example U.N. Climate Panel Endorses Ceiling on Global Emissions from the NYT or IPCC report: global warming is ‘unequivocal’ from the Torygraph, not normally a friend to pinko lefties. The denialists are fulminating, as you might expect and indeed hope (AW had eight posts on it at last count) but no-one seems to be listening; just as their various attempted “spoilers” have been ignored. So we’re where I thought we were: its easy, when you’re touring the incestuous blogosphere, to see controversy; but in the outside world there is much less.

Here’s google trends on IPCC, NIPCC, and stoat (not me, I fear):

//www.google.com/trends/embed.js?hl=en-US&q=nipcc,+ipcc,+stoat&cmpt=q&content=1&cid=TIMESERIES_GRAPH_AVERAGES_CHART&export=5&w=600&h=330

Stoats are not as popular as the IPCC, I’m sorry to say, but we totally wipe the floor with the NIPCC (who?).

The Anti-MOOC Panic

I’m not desperately interested in the “MOOC” on-line course thing, though I can see that I might be in future. I don’t have a lot of spare time; for example the 2 hours I had free last night I spent running + recovering, not learning. But others do, and CIP has been talking to “the enemy” – i.e. the tenured professors in minor universities who have the most to lose. John Boy is even more in favour than CIP. However, I don’t want to debate their virtues but do want to note CIP’s:

The flood waters in Colorado seem to have washed away my comments on yet another blog by a historian at a school (CSU Pueblo) I had never previously heard of. One thing these guys can’t stand is dissent, even politely expressed. I can’t really blame them. They are trying so hard to convince themselves that MOOCs can’t do anything right that any contrary message excites pure panic. They, the tenured profs, have a pretty good deal, even if they aren’t exactly teaching at Harvard, and they have worked hard to get it. Of course that keeps them from understanding the real weaknesses of the MOOC or guessing the shape of education a decade or so from now.

What interests me about that is that its exactly the same reaction as the GW denialists. They, too, have nothing interesting to say about their area of interest, because they are scared of phantoms. They don’t know what the weaknesses of GW are, because they are incapable of studying it. Which brings me on to my alternative post title…

On not speaking

Posting here has been thin recently. You can’t see the numerous posts I started in a brief flash of enthusiasm but realised, meh, its either just knocking back a bit more denialism, or, meh, I’m just another voice spouting off. There are plenty of people out there telling you about Syria, or why so many people are clueless about the tax system, or why so many people are scared of free markets. So this is the “misc” post.

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End of an era

I’ve been rowing again. I knew you’d want to know.

Real science

Human and natural influences on the changing thermal structure of the atmosphere by Santer et al. in PNAS looks to be worth a read. Though to be honest I haven’t actually bothered to do so 🙂

Judith Curry’s understanding of climate is not helped much by climate models

Or so she says. Personally, I find that my understanding of the deeper aspects of General Relativity isn’t helped by me not taking the time to concentrate on the maths. But at least I’m able to realise that’s a flaw in me, not GR.

Mind you, Curry’s comment does help explain why some of her papers are crap – if you write a paper in which “the model simulations … were the main source of data used in the analysis” and yet you don’t think the models help, you’re not really going to write anything sane.

Tell me something I didn’t know

The NIPCC is drivel. Oh, that wasn’t news? Never mind. Like everyone else, I’ll read a little bit (thanks to Sou there’s a copy here) then get bored. I got to:

IPCC Claim #1: A doubling of atmospheric CO2 would cause warming between 3°C and 6°C.

and thought “that doesn’t sound right”. Then I looked about – because the report, you see, is all sciencey, its got references and everything, its like a dog walking on its hind legs – and thought “hold on, Shirely you’ve referenced that” because otherwise all your stuff is just voodoo. But no, they haven’t. So much so that its not even possible to know what they mean by this – do the mean the climate sensitivity? The equilibrium one? Anyway, rather than trying to interpret denialist junk you’re better off reading the IPCC AR4 which says:

The equilibrium climate sensitivity is a measure of the climate system response to sustained radiative forcing. It is not a projection but is defined as the global average surface warming following a doubling of carbon dioxide concentrations. It is likely to be in the range 2°C to 4.5°C with a best estimate of about 3°C, and is very unlikely to be less than 1.5°C. Values substantially higher than 4.5°C cannot be excluded, but agreement of models with observations is not as good for those values. Water vapour changes represent the largest feedback affecting climate sensitivity and are now better understood than in the TAR. Cloud feedbacks remain the largest source of uncertainty. {8.6, 9.6, Box 10.2}

So its pretty hard to avoid the conclusion that the NIPCC is simply and blatantly lying. Can you think of a way to avoid this conclusion, other than by not thinking?

MacKay and Stone: Potential Greenhouse Gas Emissions Associated with Shale Gas Extraction and Use

shale A report for the Department of Energy and Climate Change. MacKay is Sustainable Energy – without the hot air person, and a rather infrequently updated blog. He’s a pretty sensible chap and the new report is a challenge to all the folk who go around unthinkingly saying that shale gas emissions mean that its worse than coal (and for the people who think at least a bit, but rely on Howarth, they provide some reasons why Howarth may be wrong). At least, if you don’t agree, you’d better have a good reason.

More on global temperature spectra and trends

From Moyhu. Interesting stuff: removing ENSO a-la F+R then looking at FFTs and noise fitting.

Kosaka and Xie, take 2

This is my take 2. See here for my incautious take 1. Take 2 is not as interesting as take 1 – I no longer have an overall theme, and I don’t feel inclined to contradict the take-home message. That reduces me to quibbling and a slight feeling of unease, though that may quite possibly be because I now feel biased against this paper for giving me a hard time.

So, take their “We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model”. But this isn’t desperately novel, nor is that quite accurate – what they actually do is restore SSTs towards the observed pattern in this region, by modifying the surface heat fluxes (and if you compare figure 2 and b closely, you’ll see that the restoring isn’t perfect; in that 2b, within the inner box, clearly isn’t the same as 2a in the same region. In fact its rather more different than you’d expect, which is odd. Ditto 3 a, b). Which isn’t new; here for example is a random example from 2006. In fact, later on they say The POGA experimental design has been used to study the global teleconnections of the interannual El Nino/Southern Oscillation (ENSO)11,12. Here we present a novel application of POGA… so I think they’ve mis-spoken in their abstract: the method isn’t new, only the application. You’d have thought that Nature-quality reviewing would have caught that. But I’m quibbling.

Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970–2012

k+x This is the bit I reacted somewhat badly to in my first go, claiming that it wasn’t surprising because the ENSO region is so important. Just to make sure that Captain Cockup doesn’t come to visit again, here are their experiments:

* (HIST) is forced with observed atmospheric composition changes and the solar cycle.
* (POGA-H) Pacific Ocean–Global Atmosphere (POGA) experiments, SST anomalies in the equatorial eastern Pacific are forced to the observed evolution, and the radiative forcing is identical to HIST
* (POGA-C) is like POGA-H, except radiative forcing is fixed at the 1990 value. In both cases, outside the equatorial eastern Pacific, the atmosphere and ocean are fully coupled and free to evolve.

So if you look at the lower figure, and compare the wiggles to the upper, they match pretty well – especially if you ignore the volcano years. Which does indeed suggest that ENSO is driving much of the interannual variability, but now I’m obliged to admit that comes with the trend coming from the radiative forcing (as, in retrospect, you’d expect). It also appears to imply that the volcanoes mainly affected extratropical temperatures for some reason, but that’s another matter.

A comment (which isn’t original to me): even attributing the change to ENSO doesn’t tell you if its forced or not: whilst ENSO is a natural mode of the system, its perfectly possible for Anthro forcing to act not to change the long-term-mean-state, but to push it further into a warmer regime; there has long been speculation that warming could manifest as “more El Nino and less La Nina”. OTOH, in this case we appear to be seeing more La Nina, and its somewhat hard to see how that could be forced; K+X address this, a little bit, in their “Whether the La-Nin˜a-like decadal trend is internal or forced is still unclear…” para.

Errm well there you have it: it looks OK to me.

Kosaka and Xie

[Ahem. Update: this was just wrong, because I misread the defn of POGA-C; see comment 2, thanks to TC. To avoid polluting the record, I’ll delete the rest of this post, but there’s an archived copy at http://www.webcitation.org/6JMTX0nGx if you like. The paper fairy has now delivered a copy of K+X to me, so I expect to post a “take 2” later this evening. Or maybe tomorrow; I might actually try reading it properly this time.]

I have a take 2 if you’re interested, but its dull.