The Big Picture

Its become pretty clear that many people are losing sight of the wood for the trees, or even the twigs, in the latest rounds of the Hockey Stick Wars. Fortunately some of the more intelligent watchers of the debates have realised they need help. So here it is.

What it the Big Picture? From the point of view of climate change, the top level is

The world is getting warmer, we're causing it, and it will continue to get warmer in the future. This is pretty well universally agreed on now.

Going down a level, the point at issue is then the various palaeoclimatic reconstructions of the [[temperature record of the past thousand years]] (or, now, two thousand). Here the important point is ...the increase in temperature in the 20th century is likely to have been the largest of any century during the past 1,000 years... and so on: which you'll doubtless recognise as a quote from the TAR. But more than that, all the headline points that the TAR made about the MBH record it used are true of all the other reconstructions too. So all the nonsense about whether the fall of the Hockey Stick would disprove global warming or whatever is just nonsense. Because there is plenty of backup. The other point that the septics do their best to push is the idea that all the attribution of climate change arises from the palaeo reconstructions. That too is nonsense, & discussed at RC. Or just read the TAR.

Going another level down, we come to the various arguments about the details of the Hockey Stick. Thats the level of the recent RC post Hockey sticks: Round 27, where we discuss two recent GRL papers. This is interesting stuff - if you're keen on statistics. If you're not, and you're baffled by the claims and counter claims, then you have two options: hop back up a level, because you've got to a too specialised for your understanding; or improve your understanding. Don't misunderstand me: there is a lot of interesting work to be done at this level. There are, as shown by the graph, a whole pile of records that agree on the main points but disagree in detail. Resolving this is an active and valuable area of research. If you're interested in policy, though, you've gone too far down. Go back.

Some people think that that the debate over the so-called "hockey stick" temperature reconstruction is a distraction from the development and promulgation of climate policy. And I agree (though I would replace "policy" with "science" cos I'm more interested in the science). And this is what we've been saying in the recent comments at RC. So if anyone were, hypothetically, to enquire why *others* should continue to care about it... Why is this fight important to the rest of us? the answer is: you shouldn't. It isn't. There: that was easy.

Oops: I forgot something and blew my dramatic ending. Sigh. There is (yet another) odd inversion about: the idea that if we were to switch from, say, MBH (less variance) to Moberg (more) that would somehow imply a reduction in expected future warming. That is completely wrong. If the past temperatures varied more, it implies a *higher* sensitivity to forcing, and therefore a *higher* future change.

[Updated to fix broken href; nothing new to see; move along now folks... :-)]


LuboŇ° Motl said...
This comment has been removed by a blog administrator.
Anonymous said...

...for Lubos personally, that he can predict given his lack of knowledge about climate science, within his lifetime. No, probably not. Actually the major direct personal impact of climate change on Lubos is likely to just be an increase in his taxes, which I guess is his point.

So William, my big question about the recent hockey stick stuff remains what in the world is going on with GRL? I don't necessarily expect anyone to have that answer, but I plan to join the AGU and attend the annual conference (conveniently local for me), where I plan to buttonhole the editor. I'm sure he or she will be thrilled.

BTW, here is McIntyre's abstract:

Methodological Issues in Multiproxy Reconstructions

We review some important and under-discussed methodological issues in multiproxy reconstructions, applying insights from recent statistical and econometric studies and considering examples in the recent multiproxy literature. Issues include: 1) 'spurious' (in a statistical sense) relationships between highly autocorrelated series, considering both regression and scaling methodologies. We discuss problems arising from proxies potentially affected by nonclimatic trends or factors and the related question of the robustness of multiproxy methods. 2) series selection and the potential problem of data mining. We show examples where variance attenuation arises without regression. The effect can be demonstrated when series are selected from a menu of persistent red noise examples and then averaged together. 3) non-linear and especially non-monotonic relationships with temperature. Each issue will be related to the problem of calculating confidence intervals.


William M. Connolley said...

GRL... yes, if you find out, do let us all know...

Anonymous said...

Dear All
Over the last few months I've been avidly reading the debate between the pro and anti-hockey stick crowd on RC and Climateaudit. I am not a sceptic in any sense (except that of seeing scepticism as being an important initial position to take in all science). It seems clear to me that AGW is taking place, and that global temps. are higher than in the recent historical past. Indeed, we would have real problems if the climate WASN'T responding to carbon dioxide emissions.

However, my view is that Steve McIntyre is doing all climate science a service. He's clearly a good statistician and (whatever his motives/politics etc) his views should be listened to. If the hockey stick is still robust after he's analysed the data then you can be sure it reflects the real climate change. I'm sure it will, as you get hockey sticks from other proxy data too (glaciers etc).

Hiding data, analyses, code, methodologies etc from real scrutiny must be counter-productive in the long run. However, I'm also pragmatic enough to know that we don't always keep our data sets (I've analysed loads of lichenometric, dendrochronological, dendroclimatic and glacier fluctuation data from Patagonia and Kazakhstan but am sure I couldn't find much of it if I was audited!).

Finally, we should employ Occam's razor in such complex issues. Overall, lots of proxies/methods show anomalous recent warmth, which is what we would expect with historically high carbon dioxide levels. It's clearly safest to suppose that they are causally linked.

Anonymous said...

Dano, has he actually said such a thing? That would be a far cry from what he's done so far, which hasn't required him to move from his computer. Even if it's just tree rings, aren't there skill sets involved with collecting and interpreting the data that would be rather difficult to acquire outside of grad school? Instead, as witnessed by the AGU abstract posted above, it looks as if he's spent much of his time recently expanding out into an attack on all of the multi-proxy studies.

Anonymous said...

Dano, I wanted to re-sample the Gaspe tree ring site in eastern Canada in 2004.

I had received information that re-sampling had been done in 1992 which did not show the hockey stick pattern of the earlier series (which is uncharacteristic of cedars anyway.) D'Arrigo refused to provide the updated information the basis that the earlier data showed the temperature increase "better".

So I asked for the location of the site so I could carry out re-sampling. They refused to provide this information. Jacoby said that the site had been sampled prior to GPS so they no longer knew where it was. He said that they had tried to re-locate it in 1992 and failed; that's why they didn't report the new data.

I asked for the location of the new site and any map information on the old site. This led to a typical Hockey Team brawl, but no information.

My plan was to get one of the cedar experts of the University of Guelph involved. I tried various means of getting a site location but was stymied at every turn. If you can get the site location, I'd be happy to get someone to go re-sample it.

Anonymous said...

The problems with Gaspe are shown here, including the updated version.

http://www.climateaudit.org/?p=41 ,
http://www.climateaudit.org/?p=182 ,

I have never used the word "conspiracy". Please don't put words in my mouth.

Anonymous said...

Dano, I agree that the impact of 2xCO2 is an important issue. I think that a detailed truly independent examination of at least one model at an engineering level would be a good idea. Unfortunately, it's well beyond my resources. I thought that the multiproxy studies looked interesting, were within my resources and have attempted to become expert in this area. You can't do everything in the world. Cheers, Steve

Anonymous said...

The wry, winking conspiracies are the best kind. :)

Anonymous said...

I just read a text by Phil Jones where he makes the point that most probably 2005 is only the second warmest in history (there is a bit of uncertainty how you compute global mean temperature or as (NH/SH)/2 or directly). Anyhow 1998 seems still to stand as the warmest year whereas on your spaghetti diagram it does not peak out.
Cheers Georg

William M. Connolley said...

Georg - not quite sure what your point is. 1998 is the warmest so far, but won't be for long. Temperature isn't expected to rise monotonically, of course, as a glance at the annual series, unsmoothed, will show. "2004" is plotted on that graph for interest, not because its warmest.

Anonymous said...

Rob van Dorland claims he has seen the resubmitted study of Wahl and Ammann. Have you?

Anonymous said...

You overlook another important part of the Big Picture, which is who can policy makers and the general public trust? If the hockey stick study is half as shoddy and dishonest as M&M claim, then the IPCC and even Nature are not reliable sources.

The best promise I see is to have some sort of venue that provides not only pronouncements from above, but also provides the arguments behind them at increasing levels of depth -- much like the structure of this article, only with multiple and sometimes adversarial authors. Then the public has access to the best information and arguments regarding all sides of all disputed points.

William M. Connolley said...

Lex - Thanks for the comment. But I think you've been reading too much M&M propaganda and too little science. Take some time to browse the IPCC report, find a bit that interests you, look up the papers that it references, and see how well they support what it says. You'll find, always, that it is well referenced. Thats why the skeptics have had so little to say to attack it.

Contrast tis with McKitrick: over at Prometheus he is saying, in a piece that makes a big virtue of honesty, "The paleoclimate field seems to have organized itself around them: other papers since then have gained prominence in proportion as they appear to back up MBH, whereas papers that contradict it have little prospect of being published or are relegated to lower-profile outlets." This just isn't true: take the Moberg study, published in Science, widely regarded (and certainly by M&M) as showing differences from MBH.

As for the adversarial stuff: its all very well, but quickly degenerates into mindless nit-picking. The IPCC TAR is the current best source of a review of climate science (I do hope you have at least broswed it, and not just the SPM) and you see how big a job that is.

The idea that climate science is monolithic with no internal debate is also quite wrong. Its just that not everyone is as hostile and publicly confrontational as the septics.

Anonymous said...

Dear Belette
what do you think ?
take the Moberg paper (published in Nature).

Is it different to MBH ?

Some people have argued that all the climate reconstructions show "the same thing". Surely, if these reconstructions show different things, one (or more) of them must be wrong !

it will be interesting to hear your view :-)

Anonymous said...

presumably, you can also quote the von Storch paper as evidence that you do not have to agree with MBH'98


William M. Connolley said...

Hello Mr Sock! Rather low-grade trolling this time.

Some people do seem to regard von S as disagreeing with MBH. And yet it was published in Science. Ditto Moberg. Which just goes to show: McK is more ideologue than scientist, as is anyone who claims that "other papers since then have gained prominence in proportion as they appear to back up MBH, whereas papers that contradict it have little prospect of being published or are relegated to lower-profile outlets".

I don't know who argues that the recons are all the same... I repeatedly pointed out that they all fit the TAR text, so you could replace MBH with Moberg and get the same result.

Presumably, some of them are wrong. It isn't necessary for all-but-one to be wrong though, as some measure different things.

Anonymous said...

I wonder, do you continue to believe that AGW is a serious issue that needs attention, or have you wised up yet?