The BBC claims a quarter of a billion people tune in to their global news service every week. That's one reason why I take a dim view of their naked enviro-political proselytizing.

HaroldW: how the blue blazes do they measure 0.3mm a year? I seriously doubt that they can see 0.3mm; I doubt a change of 3mm would be observable – even 30mm would be dubious. Should they be referring to an average of measurements taken over the longer term (say, 100 years), then how can they be sure of the accuracy of the original measurement? How can they be certain that the measurement point has not altered? I take both radar and mechanical measurements of liquid levels in more controlled environs than the sea (or the maritime coast, if you prefer) and will accept an accuracy of 10mm – any less is just guesswork, and the mechanical reading is trusted over the radar.

The only good thing about this story is that it is so patently absurd that some will have noticed, and their trust in the BBC will be diminished.

From the Ecclesiastical Uncle, an old retired bureaucrat in a field only remotely related to climate with minimal qualifications and only half a mind.

I think the BBC World Service is still paid for by the Government rather than out of the license fee. If this is the case the tone of the programme should come as no surprise since the current Prime Minister leads the 'greenest government ever'.

I know, HaroldW. Sorry. I wasn’t harping at you, specifically, but at the many, many measurements that are being used to “prove” one way or the other; some are, as in Chennai, so trivial as to be laughable. One only has to look at the blatant manipulation of temperature data to realise that: why are the older records being revised (generally downwards)? While the instruments of the time were possibly not as accurate as they are now, perhaps they were better sited (let’s face it, a field is probably a good place to have the thermometer; but, when that field becomes a car-park – well, the middle of a car-park is not really a good place, now, is it? But still it remains). I remember reading that NASA had reversed its revision (re-revised?) of earlier temperatures, and that 1935 was actually the hottest year of the 20th century; but, why did they feel that the original temperature had to be revised (downwards, of course)? And why is 1998 still being cited as the hottest?

It is the same with sea-levels: how soon before historical sea-level records have need to be “revised”? If it does happen, you can bet your bottom dollar they will be revised downwards – i.e. the sea levels in Bournemouth were not as high as the Victorians thought, after all. Hey! Perhaps they could have walked to the Isle of Wight at low tide, if only they knew that that water they could see wasn’t there!

And so on to sea temperatures – especially the deep oceans, where all the extra heat has suddenly taken a dive (for no explicable reason). Oceans are warming. We know that; they have been warming since the last Ice Age, 10,000 years ago. For some reason, this warming has become dangerous. But, how do they measure the increasing heat content? They give us fancy (and steep) graphs in Joules (or 1022 Joules). So, how is it measured in such a way? The only way I know of is by measuring the temperature; this turns out to have risen by 2/100ths of a degree C since… well… when? Nobody seems to say, only that there has been a rise of 2/100ths of a degree C – and this in an environment that we have only just begun to monitor, with sparsely-scattered instruments of unknown reliability over the long-term in an extremely hostile environment. Now, my work does involve taking temperatures, but even the biggest, fanciest thermometer I have used is only accepted as accurate to about 0.1°C (i.e. 10/100ths); the tables to which this is applied are calculated to 0.25°C, with no interpolation allowed. What is the point in declaring that a temperature rise that is essentially unmeasurable has to be considered dangerous? Answer: to whip up yet more hysteria and fear over a story that is based on lies and half-truths. Why such efforts to maintain the fear? To keep the people frightened; frightened people are pliable people.

Sorry about that rant; you just touched a nerve. By the way, the recordings are quite possibly continuous, using a float on a sensor. It’s in a dock, shielding it from the open sea, yet will still bob up and down more than 0.3mm – and probably more than 30mm, most of the time; then it will have to deal with the disturbance caused by boats…

Float or ultrasonic sensor, either way it's measuring the distance between the sea level and whatever it is fixed to, which can easily move more than 0.3 mm for a multitude of reasons from thermal expansion to settlement, but even the concept of relative motion is way beyond the comprehension of your average greenie BBC arts graduate, assuming that they were interested in inconvenient facts which don't support their narrative.

How do they measure 0.32mm sea level change? LOL, last time I looked the satellite based instruments have an accuracy of +/-10cm or more. They take multiple readings and perform some QA magic and spit out accuracy to the hundredth of a mm. O_o