Tropical Storm Zeta

This must be pretty abnormal (will it last until January?), but I don't know how significant it really is.

Reuters says there have been 6 recorded hurricanes in December, including Epsilon this year. Zeta doesn't seem likely to strengthen enough to add to that tally.

More on Japan's "Gender Equality Plan"

I've just had the interesting experience of taking part in a multi-way discussion for a radio show (my only previous similar experience was an ill-fated job interview - it's hard to give your best performance when you can hear a bunch of people on the other side of the world giggling at private jokes and their institute is next to an airport so every second question in interrupted by a plane taking off or landing). Fortunately, this time it wasn't on anything related to my real work. Instead, it was about Japan's plan for new gender equality laws - they wanted some ordinary punters as well as an expert or two and had apparently found my blog.

You can find the debate about 37 minutes into the Wednesday Thursday evening "World Have Your Say" program on the BBC World Service. I'm not sure I added much to the discussion, since we all pretty much agreed on most points and the other participants were asked first. However, having actually seen the main details of the "Gender Equality Plan" (which I hadn't seen prior to the program!) and had a few minutes to mull it over I think we were substantially too soft on it. Sure, few could complain about better maternity rights and care provision, but that is not really about gender equality, it is merely an attempt to boost the birthrate (or stop it declining further). It is not clear that there will really be anything there to address the discriminatory system under which women are generally treated as second class citizens in the workforce.

Let me explain further. Many of Japan's biggest companies operate a "dual track system" with one career track for managers, and one for clerical staff. The managers have a proper career structure and (at least eventually) get paid far more, and the clerical staff have basically no promotion prospects at all. Maybe that doesn't sound too unreasonable, but the shocking fact is that essentially all men are put in the management track, and almost no women. For example, in 1991 JAL (the flagship air carrier) hired 147 men and 3 women to the career track, in addition to 52 women to the non-career track. For the financial company Tokyo Marine Insurance, the equivalent figures were 424 men and 24 women hired to career-track positions and 553 women and no men to the non-career track (figures from here). Clearly this is institutionalised discrimination on a scale that would not be considered remotely acceptable in the UK. It can certainly be argued that societal attitudes play a role - some women don't want to commit themselves to long hours and the risk of relocation, although it's also possible that these conditions are added as a way of discouraging them rather than because they are really necessary.

It remains to be seen if their proposal to outlaw "indirect discrimination" will have sufficient teeth to address this. Otherwise, this will not be a "Gender Equality Plan" as a westerner would understand it, but rather a "Please have babies, but don't give up your menial dead-end job" plan. The fact that they feel the need to specifically mention "Doll Day" (a festival in whch young girls are basically taught that they should grow up to be a good wife and mother) suggests to me that they don't plan significant changes.

I promise I'll get back to posting about science soon, honest...

Tokyo Millenario

Tokyo Millenario is a long-established traditional lighting display which is installed in the middle of Tokyo for a week at the end of each year. Ok, it actually started in 1999 to mark the end of the millennium (a year too early, of course - but weren't we all) and proved so popular they've done it each year since. There are posters up all over the place advertising it, and we were in Tokyo today anyway, so thought we might as well have a look to see what all the fuss is about.

The nearest main station is Tokyo itself, and immediately on leaving the station - or rather, joining the queue to leave the station - it was obvious that we were not going to go the wrong way and miss the event:



About an hour later, we eventually shuffled the 2 blocks to reach the lights.



This picture really doesn't do them justice - they were much more boring and inconsequential than they appear. Folks, save yourselves the bother, look at the posters on the trains, and stay away. Or if you must go and don't mind missing out on walking under the arch at the very start, approach via a side-street half way along and avoid the queues.

More on Japan's population crash

("crash" seems more appropriate than "decline", somehow)

As a further update to my previous post, it looks like the decline in total population (even including immigration) has happened sooner and more markedly than expected, with preliminary census figures showing a year-on-year population drop of 20,000 to October 2005. This figure includes foreigners with more than 3 months of residence, so I'm not quite sure how it squares with the recent previous estimate that a small excess of deaths over births this year would be cancelled out by immigration. But anyway, it's the first fall since records began in 1920 (excepting a one-off in 1945), and it seems certain that next year will see a substantial fall.

This article suggests that the drop in numbers might be easier made up with robots than people...

Unintended consequences

The big shrine in Kamakura, Hachiman-gu, has two large ponds in front of it. The biggest has three large islands, which until recently had large trees growing on them which housed colonies of night herons and egrets (I'm no ornithologist, but they looked like these ones), and there are also white doves. In summer, the ponds are also full of lotus:



A year or so ago, the trees were heavily pruned, right back to ugly bare stumps. According to this newspaper comment, it was to discourage the birds which were considered to be making a mess. At the time I was disappointed that this attractive area would be so gratuitously uglified just in the name of "tidiness".

Walking past the pond at the weekend, we saw that the area has been taken over by flocks of seagulls and pigeons. As a consequence it's covered in bird shit, far worse than it ever was before. I can't quite say "told you so" but it can hardly be surprising that these natural scavengers have moved in to claim an open space. I only hope that the authorities learn from their mistake and allow the vegetation to re-establish itself rapidly, rather than taking the next logical step of filling up the pond with concrete.

Whither RealClimate?

RealClimate is a commentary site on climate science by working climate scientists for the interested public and journalists. We aim to provide a quick response to developing stories and provide the context sometimes missing in mainstream commentary. The discussion here is restricted to scientific topics and will not get involved in any political or economic implications of the science.

And I should make it clear at the outset that I think they are doing a really good job overall. But I have to wonder about some of the issues they've chosen to highlight recently. They have always had an inordinate focus on the hockey stick affair (from which none of the main protagonists emerge with a great deal of credit IMO), which in scientific terms is really not that important. At least this can perhaps be excused by the fact that it has been a high-profile story in the public eye, even if it doesn't really deserve to be. More recently, they have plucked a couple of fairly minor papers out of relative obscurity and thrust them into the limelight for no apparent purpose other than to tear into them (here and here). The authors' crimes? In each case, they included a throwaway phrase which appears to pose some sort of challenge to the "consensus" view. In both cases, the papers make some valid points, and I don't find the RC rebuttals entirely convincing. But it's not so much the science I'm objecting to, as the tactic itself, which I don't think is really warranted. With RC's dominant influence on the web comes a responsibility to treat people - and the issues - fairly. They risk looking more like a playground bully than an honest broker, especially with the rather obvious targetting of anything containing sceptic-friendly phrasing. It's a rare scientific paper that does not contain a single dubious sentence, and any significant error can always be dealt with by a "Comments on ..." reply within the peer-review system.

In contrast (and not just to prove I can hand out compliments as well as criticism) the Ruddiman article seems like a shining example of how it should be done - I would hazard a guess that most RC contributors think his ideas are rather speculative, but they still made room for sensible debate. Please, let's have more discussion of the interesting and/or important science, and less acting as judge, jury and executioner towards anyone who is perceived to be stepping out of line.

[Oh, ok, a few words about the science in the RC articles. The first article refers to comments by Esper et al suggesting that a more variable past would imply lower sensitivity to anthropogenic perturbations. While Esper et al's point is somewhat awkwardly made, it's not necessarily quite as stupid as the RC article implies. If the past was more variable, this could suggest that the variability of natural forcings is stronger (either in absolute terms, or in terms of the climate's response) than is currently thought. This might lead to some re-evaluation of the radiative forcing concept (which is only an approximation, not a law) and a conclusion that anthropogenic effects aren't quite as big as we think. However I think in practice we can accommodate significant historical variability without being too worried about implications for our understanding of climate sensitivity - if anything, the smoothness of the MBH98 reconstruction is harder to swallow.

As for the Cohn and Lin paper on trends, discussed here - it is hard to deny that scientists in all fields have sometimes used somewhat simplistic statistical tests and assumptions, and this provides a rich seam of opportunities for people to "rediscover" the limitations of these approaches. I recall this presentation at the EGU a couple of years ago making effectively the same point (it seems to have appeared recently as a paper here, which I've not read), and I've even discussed the issue myself on occasion. It hardly seems as cut and dried as RC's presentation would seem to imply.]

Population decline in Japan

As I mentioned recently, Japan's population is expected to drop substantially in the coming years. According to this this Japan Times article, it's now close to being officially confimed that the drop has actually started already, a year ahead of the most recent forecasts (it was only on Friday that the Govt changed the official forecast of year of first decline from 2007 to 2006). With the annual rate of population change dropping at about 70,000 per year (and this rate may even be accelerating), there will be substantial demographic changes over the coming years. Eg at this rate, in 10 years the population will have fallen by 3.5 million, and be falling by a further 700,000 each year - this on a base population of about 130 million. The prediction for the year 2100 is a 50% decline, but this is bound to be based on on some very wishful thinking about an increase in the fertility rate. It will be interesting to see what concrete measures the Govt puts forward for adaptation and mitigation in the face of this long-term challenge.

Update 26/12

It seems likely that this "population decline" headline is slightly misleading. Even if deaths outnumber births, net immigration is likely to keep the total resident numbers rising slightly this year. Here is an article discussing the issues:

Conservatives eager to preserve what's left of Japan's "man at work, woman in the home" family model have been loathe to vastly expand the day-care system, for instance, for fear of encouraging more women to join the work force.

Another obvious possibility - loosening Japan's tight immigration laws to allow more foreigners to come here to work - has been blocked by a widespread distrust of outsiders and fear that foreigners would disrupt the country's social order.

Power from nothing?

From Treehugger I find this "Electro-Kinetic Road Ramp" which promises free power generation due to the action of cars passing over it. The ramp flexes as the vehicle moves over it, and is connected to an electrical generator:



I know I joked previously about the car-mounted wind generators on show in Japan, but in that case at least they were clearly designed as a promotional exercise rather than a serious attempt at power generation. These guys, on the other hand, are for real! Listen to the voice-over on the movie if you don't believe me - this is not being presented as a convenient way of powering off-grid road signs in remote areas, or a way of making speed bumps slightly useful. They actually claim "free electrical energy" and suggest installing them widely in cities:

...designed to generate electricity using kinetic energy from passing traffic. This energy, which is free, would otherwise be lost... The ramp...consumes no aditional fuel, produces no emissions, and is environmentally friendly.

I hope it doesn't really need pointing out to my reader why this is bogus - the ramp steals energy from the passing vehicles, meaning that their fuel consumption is necessarily increased and it's a racing certainty that the overall efficiency of power generation from oil to electricity is way below that of a competently designed power station, for example. I am astonished that anyone with the technical competence to actually design and build such a construction should not be aware of the fundamental physical law that it claims to break.

As an aside, I can't imagine that it would be much fun to cycle over one, still less with a car overtaking simultaneously. But I'm optimistic that no-one will actually get taken in by their claims.

Update 19/12

According to this BBC news article, my assessment of the competence of local authorities was badly misplaced:

More than 200 local authorities had expressed an interest in ordering the £25,000 ramps to power their traffic lights and road signs, Mr Hughes said. Around 300 jobs are due to be created in Somerset for a production run of 2,000 ramps next year.

What a bunch of numpties. I can only hope the manufacturers go bust before too much taxpayers' money gets wasted on these stupid contraptions. Even from the local authorities' narrow viewpoint (ignoring the added cost on the motorist, and the pollution they will generate), the payback time will be decades.

Nature on Wikipedia

Chris Masse tipped me off that the new Nature contains this article by Jim Giles talking about Wikipedia, and in particular comparing its accuracy to Encyclopedia Britannica. Wikipedia has been in the news recently due to its containing a spoof page alleging a journalist was involved in the assassination of two Kennedys, so some might be surprised that Nature found its overall standard to be not far behind its more illustrious (and expensive) cousin in terms of the number of mistakes identified by reviewers.

The accompanying box (link) "Challenges of being a Wikipedian" mentions William Connolley's involvement in the "climate wars". The fact that Wikipedia works at all suggests to me that most errors are due to ignorance rather than malice, but a handful of trouble-makers can clearly make quite a nuisance of themselves. I'm not really convinced that it's worth the effort but I'm glad someone else is :-)

There's some slightly odd spin in the Nature article, on the number of contributors:

As well as comparing the two encyclopaedias, Nature surveyed more than 1,000 Nature authors and found that although more than 70% had heard of Wikipedia and 17% of those consulted it on a weekly basis, less than 10% help to update it.

A figure in the region of 10% seems like an extremely high contribution rate to me. I would have probably bet on 1% or lower - and how many contribute to usenet or other interactive internet-based media such as blogs, I wonder? Note that this figure represents about 80% of those Nature authors who actually use it regularly (17% of 70%)! In contrast to his tone, I find such a high participation rate to be very encouraging.

The article mentions that the organisers plan to introduce "stable" versions of pages once they reach a high enough quality. In the meantime, here's a small tip for users: when referring to a Wikipedia page, always use a specified version rather than linking to the current editable page (you can get a permanent link to the current version from the "permanent link" in the "toolbox" on the LHS of the page, or use the "history" tab at the top to look though older versions - eg here is a decent page on the Earth Simulator, but this version - although identical at the time of posting - may be changed at any time). That way, at least you know your readers will get to see what you saw, rather than some potentially very different (possibly vandalised) version. Checking the history also allows you to see how controversial the page is. Of course this doesn't ensure that the information is correct, but anyone who bets the farm based on a single unverified web page pretty much deserves what they get anyway.

Oops

One thing that Japan really isn't very good at is banking (UK residents who think their banks are bad, like those who think the National Health Service is good, should try living abroad for a while to realign their perceptions). Here's another blunder by Mizuho, throwing away a year's profits with a single typo. Until recently they were the largest bank in the world - they haven't actually thrown away enough money to drop to 2nd place, another mega-merger overtook them. Mizuho themselves were formed by a merger of several banks a few years ago, at which point their electronic systems crashed and no-one could access their accounts for a while.

Guess who banks with them? Yes, yours truly. But I'm thinking of upgrading to an under-the-mattress account for easy access and extra security :-)

Bryden won't bet on cooling either

For those who've been asleep, or on Mars, for the past week, I'm talking about this paper which I mentioned here, and the associated press coverage such as this Guardian article. I've deliberately linked to the google cache in preference to the current page because while writing this blog I've noticed that the page has changed subtly. The original version had the sub-head Temperatures in Britain likely to drop by one degree in next decade but this has now been removed. If the googlc cache has changed by the time you read this, you can find the original text quoted here (googling on the exact phrase brings up several copies). The text of the article attributes this prediction to Professor Bryden, but only with an additional qualification: If the current remains as weak as it is, temperatures in Britain are likely to drop by an average of 1C in the next decade, according to Harry Bryden. Even though there's no clear indication there whether he actually expects the circulation to stay this weak or not (and indeed there's no guarantee that he was correctly quoted at all), I thought there was enough of a question-mark to make it worth enquiring as to whether he really did expect such a cooling to occur.

From his rather curt reply, it seems clear that he is not prepared to consider a wager at all.

[I'm going to be pedantic this time and refer to the circulation in question as the North Atlantic Meridional Overturning Circulation (MOC for short). The name "Gulf Stream" is IMO best restricted to the rapid surface current flowing north in the Caribbean/Gulf of Mexico area close to the east coast of the USA. Some of this doesn't get very far north before returning south at or near to the ocean surface (essentially forming a large clockwise gyre in the Atlantic), but the rest continues flowing further north, up to the latitude of the UK and beyond. This bit, sometimes called the North Atlantic Drift, is what keeps NW Europe mild in winter. When the water gets cold enough, it sinks (is mixed with deep water via convection) and returns at depth (there's a diagram here, described in this article by Stefan Rahmstorf). It is this northerly branch that Bryden claims to have decreased markedly, based on estimated changes in how the return flow varies with depth (more of it is coming back near the surface, implying a stronger subtropical gyre and weaker MOC). One possible mechanism for this would be if the surface water is freshened by increased river flows and ice melt near the limit of its northern extent - fresh water is less dense than salty, hindering convection.]

Anyway, there seem to be three cases to consider:

A) The MOC has decreased and will stay weak (or weaken further) in coming years/decades
B) The MOC has decreased but will increase again in the near future
C) The MOC didn't really decrease at all, the measurements (or their analysis) are inaccurate.

I think everyone agrees that case A implies a strong cooling for the UK in the near future. In fact many people have suggested that the reduction, if real, should have already caused some noticeable cooling, given that the decrease is supposed to have happened over the past several decades (half the measured change was in the interval 1957-1992). My money would have to be on case C, but I'm not sure what Bryden and his co-authors think. His paper certainly mentions the possibility of observational inaccuracy, saying that "the observed changes are uncomfortably close to these uncertainties", but follows this immediately with "but [foo] and [bar] represent strong arguments that the observed changes are robust". But although he argues that the MOC really has decreased, he's not prepared to bet that temperatures will drop. I don't think anyone has proposed a plausible argument for the MOC increasing again soon, if it really has decreased (case B), but it seems to be the only option left open to him.

Reputable? Surely not!

I'm rather amused to see myself described as a "reputable sceptic" on this blog. I don't know anything about the author, a bit of idle googling merely reveals that he frequents the blogosphere. The epithet is linked to my comments on the recent thermohaline circulation switch-off paper, but I'm puzzled as to where the "sceptic" tag comes from. Of course in the literal sense, every decent scientist is sceptical, but I don't think I've got much in common with the denialist camp that is usually associated with this term. On the THC subject in particular, I think my opinions are pretty well slap bang in the centre of the mainstream scientific opinion. See for example Realclimate's similar thoughts on Bryden et al (and note particularly Martin Visbeck's comment) and Stoat too. Richard Wood also sounds more than a little dubious in this NewScientist article. Not that my opinions in any way define or even influence the scientific consensus on this topic: far from it, I'm barely a bit-part player. The new THC results are interesting, but surely far from the last word on the subject. In fact, if I was a betting man (and rumour has it that I might be), I would put money on future results indicating a much smaller or even negligible effect.

And for the rest of climate science, "sceptic" seems even harder to justify. Sure, I've poked a bit at what I see as one or two excesses from the alarmist wing, but not half as hard as I've kicked at the septics who lie and dissemble and run away when challenged to back up their beliefs with hard cash. It's early days, but I am optimistic that the forthcoming IPCC AR4 will represent a balanced summary of the state of climate science that I will struggle to find much fault with, as the TAR before it did. I would have thought that such a statement pretty well rules me out of the sceptic camp. I'm not sure that "traditionally pro-warming scientist" is quite the best choice of words either, but the intention seems clear.

So if he thinks I'm a sceptic, I wonder what he thinks the mainstream is - Greenpeace, perhaps, or the Monster Raving Green Party?

Leaves

Japan has fabulous autumn colours and weather to match, so we walked in to the station one morning a few days ago and took a few photos on the way. This on the left is a ginkgo tree in someone's garden a few minutes down the road (with a typical autumn sky behind). The nuts can be roasted and eaten, and are often found at roadside stalls at this time of year. Curiously, the kanji in the Japanese name for the tree can be read as "gin" and "kyou" ("golden apricot") and the nut itself (which uses exactly the same kanji!) is called "ginnan" but the name "ginkgo" isn't understood here - they call the tree "ichou" instead. The brilliant golden leaves are among the first to change - in fact most have fallen now.

Our local bus-stop is beside the shrine Kamakura-gu, which has a good Japanese maple (momiji) outside. Before coming here, I used to think these trees were a miniaturized version of the larger Canadian equivalent. But here they grow into a fair size, albeit slowly. I suppose the ones in the UK are mostly young. Usually we get the bus from here, but it was so bright and sunny that we continued wandering through the back streets towards...

...Hachiman-gu which is Kamakura's most important shrine, where millions (literally) of visitors come at the New Year (quite a sight - the whole town centre is closed to traffic, and the main street from the station is absolutely packed with people). Here's another momiji beside a bridge at one of the shrine's two ponds.

Pensions and power stations

Two apparently unrelated items of news this week in the UK got me thinking that perhaps all was not lost as far as climate change (and indeed Government competence and willingness to to its job) is concerned. And I say that as someone who would not have voted for Tony Blair in the last election even if I'd had a vote to waste use.

The first is pension reform. It's long been clear that something had to be done, with people living longer, and no increase in the number of workers (through population growth and/or immigration) necessary to keep them in the style to which they would like to become accustomed. The Govt seems to be heading down the obvious and entirely appropriate path of staged increases in the state pension age, perhaps raising it to 68 by 2050. This in itself won't be quite enough (or indeed acceptable) while they maintain their present unsustainable retirement age of 60 for all public sector employees, but it's always struck me as a stupid waste of ability to throw people out of work at such an early age and I'm sure this will change too (this rule applies to scientists such as me, assuming I return). In fact, it's often even worse than it sounds, because the early retirement packages are attractive to anyone past the age of about 54. Prior to coming to Japan, it seemed like the number of early retirees at my lab substantially outweighed those who survived to full term. For a lab with a budget deficit, it makes some sense (in the short-term) to replace an old expensive employee with a youngster on half the salary. The retiree also gets about half his old salary as pension, but this doesn't come out of the lab budget. So as far as the national economy is concerned, the net result is the same payment for (probably) less good work. But the lab stays afloat to struggle on for another year or two. If this sounds grim, it's because it is :-)

Of course, I'm not against people retiring as early as they want to, so long as they can afford it. Us scientists are certainly lucky to get paid for what sometimes feels like a hobby, and I'm sure that some people don't enjoy their work as much. I don't much fancy 30 years of golf, but I don't discount the possibility that I might feel differently in a few more decades. Anyway, a more gradual wind-down seems more sensible to me than a sudden stop, at whatever age. My father-in-law is still working quite gently in a university department at age 75 - he goes in about one day a week or so, and churned out his 100th paper not long ago (and in fact Jules and I co-authored one of the previous ones, which was fun). That seems like a very civilised approach to retirement. But anyway, I digress.

The other issue which has hit the headlines is the fuss over nuclear power. Many of the UK's existing nuclear power stations are due to close by about 2020, and with the North Sea gas also running out, new nukes is one obvious option. It's not without problems of course - mainly opposition from various environmental groups. I'm certainly not overly keen (it seems to me that the level of funding they seem to require could be usefully applied to research into renewables, which are now close to the point at which they could make a real contribution eg, not that the UK is particuarly well-suited to solar power). Nuclear power should cut CO₂ emissions, but perhaps not by as much as one might hope, due to the energy demands of extracting the fuel (plus construction and disposal, I guess).

The point I want to draw from this lengthy ramble is the encouraging fact that the Govt is prepared to take a long-term view - not something that any politicians (and especially the present crop) have often been accused of. 50 years into the future is usually way off the radar and even 2020 is far off. On this time scale, climate change becomes a significant consideration, and it is possible that we will see the meaningful debate that has so far been largely absent. The emissions argument is already being used as a justification for more nuclear power, although it's been said that the possibility of rising sea level may also interfere with using some of the best coastal sites (actually, I find it hard to believe this is really a serious issue given the rate of a few mm per year - note that we have a 6 metre tidal range in some places). I'm not sure if this is Tony Blair trying to create a lasting legacy, or simply not caring about re-election. Either way, I think they deserve some credit for at least being prepared to address the problems, whether or not they choose exactly the solutions that I would prefer. In contrast, here in Japan, the long-anticipated population crash has already started a couple of years ahead of schedule. The population is declining (for the first time ever, near enough) and the proportion of retirees is rocketing. With lifetime fertility now below 1.3 children per female (replacement rate being about 2.1) this is shaping up to be a crisis of epic proportions compared to the UK's relatively stable situation. And what do we have in the way of planning? Occasional giggles in the scandal-sheets over how some naughty politician or other has been caught not paying into the voluntary-compulsory national pension scheme that everyone knows cannot possibly cope with the future demands. As for the pension rights of foreigners - that can only be described as state-sponsored theft, but that rant is for another day.

Disappointing ruins

Just about everyone who has spent any time as a tourist in the UK will recognise this sign:



It's one of a set made by a couple of strange people, featured on this BBC News webpage.

Thanks to my brilliant sister for spotting this. Her Youth Hostel in the Duddon Estuary (on the edge of the English Lake District) is surrounded by dozens of interesting things to see and do, including some very exciting ruins and a nature reserve containing the elusive natterjack toad, which she recently was awarded a "Green Oscar" for looking after.

Thermohaline circulation switch-off?

Well, this Nature paper seems to be flavour of the week in the science news. It's an analysis of some measurements which seem to indicate a dramatic reduction in the thermohaline circulation which helps to keep western Europe mild in winter. Of course, such a scenario was (over-)dramatised in the film "The Day After Tomorrow" last year. So, are we about to enter a new cold spell after all? Personally, I doubt it, but maybe I'm not quite as sure as I was :-)

I should make it quite clear that I'm not going to be presumptious enough to criticise what they've done - the work looks fine, and they are up-front about their estimated uncertainties in their result. But the press does seem to have gone overboard on what is an interesting, but perhaps slightly anomalous result. Firstly, I would never want it to be thought that I prefer models to measurements - quite the reverse - but such a strong effect seems a bit unlikely, given what is understood about the dynamics. The 30% reduction in overturning circulation that they infer is a realistic estimate of the response to a century or more of substantial future warming, but no model suggests anything of this nature under recent historic conditions. In fact, according to these new figures, all of the slow-down happened prior to 1998, and half of it prior to 1992. Since 1998, things have not changed significantly. Assuming a drift speed of 3cms^-1 (feel free to correct this calculation), 10 years represents 10,000km of travel, plenty of time to cover the distance from tropics to UK latitudes. But there hasn't been any significant cooling observed yet in the northern Atlantic, let alone the UK climate.

I also have to say that I'm increasingly jaded about the type of stuff that gets published in Nature. Sure, this is easily (and indeed correctly :-)) dismissed as the bitter and twisted response of someone who's never likely to get published there. But their deliberate policy to select only the most "exciting" results, which are then picked up and amplified by the press, pretty much guarantees that the outliers are given a prominence that substantially overstates their true significance (I'm wondering if I should even draw attention to this again, or if it would be more polite to let it die a natural death). When all the world's climate models predicted a steady modest decline in THC which would only partially offset the future warming, it only rated an unheralded paper in GRL. I don't see this new work in itself as being enough to justify the suggestion that the UK Govt should now start planning for a colder, rather than warmer, future. And talk of a "smoking gun" also seems a bit premature. The uncertainty in the analysis is "uncomfortably close" (their words) to the observed effect, and that's assuming they haven't underestimated their errors, which is always a possibility. But it's certainly interesting, and I look forward to future analyses.

Update

Oh ok, time for a minor nit-pick that I thought of while cycling home. They infer a change of about 8-9Sv which they admit is "uncomfortably close" to the error estimate of 6Sv on each value. But (unless I've misread something) the 6Sv refers to the uncertainty of each value individually, so the error on the difference between two values is 6*sqrt(2) = 8.5Sv. That's a bit more than uncomfortably close to the estimated change, in my book. Set against that, both the recent values are low and both the first two values are high, so I'm not claiming to have completely wiped out their result with a spot of mathematical sleight-of-hand.

Update 2

I see RC also give a somewhat guarded (and more scientifically detailed) assessment here.