My post about the possibility of the Gulf Stream switching off elicited two interesting emails.

Quentin pointed me to a letter in the Economist from Professor Carl Wunsch, an MIT oceanographer, which said, in part:

The Gulf Stream is a wind-driven phenomenon (as explained in a famous 1948 paper by Henry Stommel). It is part of a current system forced by the torque exerted on the ocean by the wind field. Heating and cooling affect its temperature and other properties, but not its basic existence or structure. As long as the sun heats the Earth and the Earth spins, so that we have winds, there will be a Gulf Stream (and a Kuroshio in the Pacific, an Agulhas in the Indian Ocean, etc).

Shut-off would imply repeal of the law of conservation of angular momentum. The primary mechanism of heat transport in the ocean is the wind-forcing of currents that tend to push warm water toward the poles, cold water toward the equator. Widely disseminated and grossly oversimplified pictures showing the ocean as a “conveyor belt” have misled people into thinking ocean circulation is driven by a sinking motion at high latitudes. A comprehensive literature shows that with no wind, heating and cooling could produce a weak flow, but one not at all resembling the observed circulation.

If the sinking motion at high latitudes were completely stopped, by covering that part of the ocean by sea ice for instance, there would still be a Gulf Stream to the south, and maybe an even more powerful one as the wind field would probably then become stronger. If the sinking were stopped by adding fresh water (a deus ex machina often invoked to change the climate), the Gulf Stream would hardly care except in so far as the wind system changed too. The amount of heat transported by the system would shift, but could not become zero.

Many writers, including scientists, toss around the words “Thermohaline Circulation” as though they constituted an explanation. In the ocean, most of the movement of heat and salt, the real Thermohaline Circulation, is driven directly and indirectly by the wind field. Thus the Gulf Stream, and hence the wind, rather than being minor features of oceanic climate are best regarded as the primary elements. Many real climate change effects exist and require urgent attention; focusing on near-impossible Gulf Stream failure is an unproductive distraction.

My son Brian wrote to point out the irony that GulfStream is the brand name of a very successful executive jet aircraft!

Global warming poses awful threats to many poor parts of the world (for example, Bangladesh). For Britain and Ireland, however, a more direct threat is the possibility that the Gulf Stream might switch off or reverse — something that could happen relatively quickly (and has happened before). In which case my beloved Kerry would start to resemble Sweden. So this report is scary.

Scientists have uncovered more evidence for a dramatic weakening in the vast ocean current that gives Britain its relatively balmy climate by dragging warm water northwards from the tropics. The slowdown, which climate modellers have predicted will follow global warming, has been confirmed by the most detailed study yet of ocean flow in the Atlantic.

Most alarmingly, the data reveal that a part of the current, which is usually 60 times more powerful than the Amazon river, came to a temporary halt during November 2004…

Horse-sense on Creating a compelling presentation, book, article…

You are in a dimly lit room. You are alone on a stage before an audience of 1,000. 10 minutes into your presentation, your hands no longer shake or sweat. This is going well, you think. But just then you notice a vaguely familiar sound–tap, tap, clickety-clack–which in one horrifying moment you recognize–it’s your audience. IMing, checking email, live blogging (“wifi sucks at this hotel and OMFG this is the most boring speaker ever”)

What went wrong? How did you lose them in the first 10 minutes? How can you get their attention?

Follow the link for some useful ideas on how to do better.

From Jon Henley’s diary…

Overheard, in a CNBC interview the other day, the Leader of the Free World. Host: “I’m curious … Do you use Google?” George Bush: “Occasionally. One of the things I’ve used on the Google is to pull up maps. It’s very interesting to see – I’ve forgot the name of the program – but you get the satellite, and you can, like, I kinda like to look at the ranch. It reminds me of where I wanna be sometimes.”

I went to the Tanner dinner in Clare Hall this evening. The German Ambassador to Britain gave a nice little speech, in one part of which (about tolerance needing to start early in life) he told a story about a recent visit to Kosovo where, on entering a school, he heard a group of children singing a sweet little song in Albanian. He asked his translator what they were singing. The translator looked embarrassed, but the ambassador pressed him. “Well”, he said, “they’re singing about how when they’re older they are going to cut the heads off Serbs”.

… in 2001, the iPod was launched.

… in 1993 a suicide truck-bombing at Beirut International Airport in Lebanon killed 241 U.S. Marines and sailors; a near-simultaneous attack on French forces killed 58 paratroopers. The attack led Ronald ‘Hopalong’ Reagan to withdraw US troops from Lebanon.

… in 1956, the Hungarians revolted against Soviet rule, with predictable results. The USSR, taking advantage of the West’s distraction in Suez, crushed the uprising without much trouble. I was ten at the time, and I remember standing in our kitchen in Donegal listening to the news with my mother. “What will happen, Ma?” I asked. “Oh”, she replied calmly, “the Americans will help them”.

Now here’s a really useful gadget — a marmalade spoon. And no, it’s not something left behind by Uri Geller. Quentin produced it the other day when I arrived seeking breakfast (and a sneak preview of his Nokia E61).

Bet the money’s good, too.

Photographed on the way home the other day.

Harry Pearson has a wonderfully surreal column about Wayne Rooney. Sample:

These days the top players do not even do their own Little Britain impressions, and they leave the cutting off of the centre-back’s flashy ties to one of their people. This is not because they are lazy. It is because they are focused. The modern player is a specialist. He has little time for anything other than honing the key skills of his profession: shooting, shouting and looking sultry in styling mousse. Nothing distracts him from his job. He has a ghostwriter to write his autobiography and a ghostreader to tell him what is in it.

Some of the biggest names are now so totally devoted to themselves that they even employ a staff of experts to sleep with women for them. “Clearly the players are red-blooded young men who would like nothing better than to chase skirt,” reveals one insider close to the source of a friend, “but as professional athletes they are worried that a night of vigorous heterosexual activity might mess up their aggression, their stamina, or even their hair.”

Some have gone one-step further. A lot of fans and media people have expressed the view that Rooney is experiencing a lack of form. They are quite wrong. Wayne is in the form of his life. Unfortunately his body double is going through a sticky patch, though admittedly not as sticky as the one Frank Lampard’s body double has been experiencing for the past five months.

Some will find the news that Rooney and Lampard actually have body doubles out on the field something of a surprise. It is hard to see why. It has been common practice in Hollywood for years. You wouldn’t expect Angelina Jolie to do her own stunts, or Mel Gibson to show you his own bottom, now would you? Like any movie star Wayne is an incredibly valuable asset. Neither Manchester United nor England can afford to put what we must learn to call “the core of the Rooney brand” at risk by actually allowing him to run around on a slippery surface with a lot of rough blokes. The insurance premiums if they did would be crippling. His beard alone had to be underwritten for £77m…

This is the entry from the Admissions Book of Christ’s College, Cambridge for 1827 confirming the admission of Charles Darwin as an undergraduate. It’s just one of the amazing riches to be found on The complete work of Charles Darwin online.