climate science
stoat | July 6, 2006David Appell has a post on What if GW Were Natural? but I think he misses the main point: if its natural, then there is no reason to expect it to continue. If its anthropogenic, the we have a fairly good idea of the various forcing factors and can take a reasonable stab at predicting the future. If its natural, then for some reason GHGs produce less forcing that we expect, and unknown natural forcings produce more, and we have no basis at all for prediction.
stoat | July 3, 2006There is a new paper out (Transient Climate Simulations with the HadGEM1 Climate Model: Causes of Past Warming and Future Climate Change) in J Climate on climate change - past century and next - as simulated by HadGEM1. This reaches the standard conclusions: whereas the effects of a combination of anthropogenic and natural forcings on the climate system could explain the evolution of global mean temperatures over the twentieth century, natural factors failed to explain the warming observed over the second half of the century.
However, they also appear to have taken seriously some other…
stoat | June 30, 2006With hurricanes over Czech and Rain in New Mexico and the truely bizarre shuttle flying even though unsafe, is there any time or space for another round of hockey stick wars? No... don't go away, its interesting, really it is!
There is an exchange of letters in the most recent Science, between Rahmstorf and von S (et al. (curiously enough I've just noticed that Simon Tett is one of the al.; presumably because of the HadCM3 use)). Sadly "exchange" isn't quite right: just a letter and reply. This is a clear case of where it would be nice to see a more extended exchange to pick at the areas of…
stoat | June 5, 2006So says Science. But for the life of me I can't see why. Hat tip: CB and (!) LM.
Its based on preliminary results from ACEX. Which says... drilling revealed that the latest Paleocene to earliest Eocene boundary interval, well known as the early Eocene Thermal Maximum (EETM), was recovered. During the EETM, the Arctic Ocean was subtropical with warm surface ocean temperatures. I'm not quite sure why this is supposed to be a problem for the modellers though.
Very few people run climate models back then; I don't suppose the boundary condtions are known very well. So quite why the conclusion has…
stoat | June 2, 2006We had a talk at work today by a chap (eminent mathematician I think) about looking at the distribution of extremes in the temperature record and trying to say something about detection. The problem is that extremes are statistically rather unstable and all he could say was that he didn't detect GW; he didn't appear to understand that all that means is that his method isn't very powerful...
[Update: JF points to http://www.arxiv.org/abs/physics/0509088 which is the paper]
And when I say global, actually he was looking at Philadelphia, daily data, last 125 years. He pretty well went out of his…
stoat | June 1, 2006Swisseduc.ch has some nice pix of retreating glaciers over the last 30-odd years. No, its not *proof* of GW, of course; just more evidence in the same direction.
stoat | May 11, 2006The grauniad has an article in the IT section about "A cracking alternative to cement". They claim that cement is 10% of anthro CO2 (or 5-10% lower down; although that includes asphalt, which for some reason counts as cement based. Odd) is from cement. That didn't fit with my memories.
So I dig out the trusty IPCC report and find maximum in 1997 of 6.6 PgC/yr (0.2 PgC/yr of this was from cement production) which is about 3%. Of course, being a newspaper the grauniad (all together now...) doesn't bother cite a source for its data, so its hard to check up. Maybe things have changed dramatically…
stoat | May 4, 2006This is about "Model projections of the North Atlantic thermohaline circulation for the 21st century assessed by observations" by A. Schmittner, M. Latif, and B. Schneider (here if you have a GRL subscription). Its interesting for two reasons: another data point on the "will the THC shutdown" (no); and because of the way it weights multiple AR4 models.
What they are interested in is the size and probability of a THC slowdown over the coming century. To do this they look at 9 models (some with multiple realisations) from the AR4 archive under SRES A1B. The end result is a weakening of the THC…
stoat | May 1, 2006RC had a recent post about some errors in von S's Science '04 article. Now Salon.com has an article on it too, being nice to us. Jolly good.
The main point made is a statistical one - read RC for that. A second one is the error in the initialisation procedure for von S's model run (not sufficiently spun up back to pre-ind). This causes a drift (down) during the sim, which over-estimates the variance. But von S has also said According to our computer models temperatures fluctuated more strongly and faster. 900 years ago they were almost as warm as today. But now we know why his model says that…
stoat | April 19, 2006It constantly amazes me how completely cr*p the climate septics are. I dont mean the skeptics - e.g. Lindzen, who is a better met man than me, though he has gone a bit emeritus recently - I mean flacks like Milloy. If you want to be skeptical of GW, then the only real point at issue is "will be be a (very) bad thing". That encapsulates two points: how large is the climate sensitivity, and how will the balance of good and bad effects work out, regionally and globally (and, in a hat tip to RP, but also to others, how large are climate effects in the face of rapid societal change anyway?) (this…
stoat | April 6, 2006 To start off, an image from the commercial district. Sorry I couldn't centre myself properly.
Zorita (and von S): ECHO-G-II fits NCAR quite well (ECHO-I has higher T during MWP-ish; no mention of HadCM3) and he explicitly notes the hockey stick shape. HadCM3 comes in a bit later, and if you look at the scale the mag is half ECHO; but this is not mentioned. There is a note re un-detrended vs detrended - undetrended method underestimates less. Notes Mann et al (RegEM) with CSM, which has a lower bias than von S, and *they think* that it *may* be the non-detrending. They say, they have not…
stoat | April 5, 2006 A view of the cathedral, which looms up over the streets on my way to the U-bahn.
Start off with a pile of global radiation / global dimming / global brightening, and indeed moisture trends (the best dataset for soil moisture comes from the FSU cos they cared about their wheat fields). A model works better to simulate soil moisture trends (increasing) if dimming taken into account.
Put up my wildly exciting sea-ice and AR4 models poster and browse amongst the others. Bit of a misc morning.
Crucifix: looking at climate sensitivity. LGM climate sens in models do not seem to be related to…
stoat | April 5, 2006A few pics, just in case you think that Vienna is all beauteous; here I choose about the least attractive angle to see the Austria Centre from. . And a maybe irridescent cloud. Not sure. And Richard Alley, from his medal talk. And a slightly nicer view of the conf centre (can you spot it?) from the Donaupark .
Poster: sondes. The Vaisala RS92 produces different answers to the much-used RS80, though mostly above the troposphere. Will this matter? Fans of sondes will read .../RSO-IC-2005_Final_Report.pdf, though apparently this doesn't include the RS80.
Another poster: was the Younger Dryas…
stoat | April 4, 2006Tuesday morning has at least 4 sessions I could have been interested in. Leave EPICA for later and start off (cos I happen to pass the room) with Latif on MOC; which to me provides more evidence not to worry about it. Thence into the climate sensitivity session, which is packed.
Matt Collins talks about the Hadley work on perturbed-physics models for climate sensitivity, and shows that by and large QUMP spans the parameter space of the AR4 models. So we only need HadCM3 :-) (note: some of this stuff is my interpolation into peoples talks, so you'll have to be careful what you read). Knutti…
stoat | April 2, 2006Testing testing... is the EGU wireless network working? Yes. Good. Unlike the mike of the current speaker :-(
Anyway, following a late (1 a.m.; flight delay, then the Ryanair coach took the backroads to avoid the motorway tolls; then dumped us on the outskirts of vienna) arrival at my hotel, and an early start (6 a.m. UK time; once again I forgot to pre-register; but this year the registration is very fast due to automation, even though I forgot my cosis-number) I get to the end of my parentheses... I mean I get to the conference. Its now a bright sunny morning.
Usually I'd have checked the…
stoat | March 30, 2006Its not often I get a paper into Science (although admittedly I'm last author) so I'll mention it here: Significant Warming of the Antarctic
Winter Troposphere J. Turner, T. A. Lachlan-Cope, S. Colwell, G. J. Marshall, W. M. Connolley, 31 march 2006, v311. The paper is mostly observational, I did a little bit of looking at the GCMs, with inconclusive results.
So there it is. Don't over-interpret it. Oh, and see-also the BBC take.
[Update: this is now up on RC in slightly expanded form; so you can choose where to comment!
stoat | March 17, 2006So... where to start? Back in the dim and distant days of a year or so ago, or back to the TAR, there was a problem: temperature trends at the surface and upper atmosphere were incompatible with how the models said they should relate: the models said the upper trends should be larger, obs said otherwise. As it happened (see here and here) the models (and the surface record) ended up triumphant (to somewhat oversell it); and the upper air obs got revised.
But in between the recognition of the problem and its resolution, the CCSP decided to convene a panel to look at the problem and see how it…
stoat | March 8, 2006A tip-off from G, whose habit of trawling the dark and smelly places of the web hauled up Common sense on global warming from the deeps where it had been deservedly sunk. The follow-up A dilettante debates the scientists is amusing too, as the self-described "autodidact, polymath, and armchair philosopher" sets to work demolishing himself (the "twin paradox" section is wonderful).
Most of the post is an appeal to the "dumb america" fallacy (I ought to hat-tip someone for this, but can't remember where I got it from - please remind me someone): the idea that while all those scientists may…
stoat | March 3, 2006The paper-for-today is Isabella Velicogna and John Wahr, Measurements of Time-Variable Gravity Show Mass Loss in Antarctica. Both Chris Mooney and Kevin Vrames have things to say about this washingtonpost write-up; I'll try to talk about some different aspects.
First of all, this is only 3 years of data; to make any sense of it, you have to assume that this is representative of the long term trend. Suppose we do this. What washpost, and the Grauniad, and every one else seems to have missed is that this just tells you, if we take the paper at face value, that Antarctica is losing mass, at 0.4…
stoat | March 2, 2006...says James Annan, and he and Julia Hargreaves have a GRL paper to prove it, not to mention a barometer dropped from a tower :-)
James directs his main fire at those who have suggested rather high climate sensitivities - 6 or 10 oC. However, this is also a blast at the skeptics who argue for implausibly low values.