Recently the good Professor posed a question to me on Twitter. I’m afraid I didn’t identify him at once, but he’s come back and posed it again.
1. Sadly, you seem to have got the wrong end of the stick, Roger. My question to you, “Come on Roger, you can do it: show you know at least a little physics and can think at least marginally,” was apropos of a very specific, really rather simple question. Namely, why do NASA’s measurement of rising ocean levels give systematically different answers when they calculate the effect using a gravitational probe as compared to the direct measurement of ocean height? In fact, here’s where I ask it and show the data in question.
If you would care to address that straightforward question, I’d be happy to engage with you on the altogether more complex misunderstandings that you lay out in this blog post.
So I am happy to reply.
Dear Professor Merrifield,
I am sorry that you feel I ignored your question as first asked. I ignored it because it seemed completely irrelevant – and also, I have to say, because it seemed to me to be couched in rather patronising and divisive terms. (People who take debate seriously do not usually start out by characterising their opponents’ arguments as “misunderstandings”). I have not written – at least recently – about the issue of sea level rise. I do not claim any expertise in the area. I have no experience of gravitational probes. And I see no reason to answer trick questions from astronomers – or indeed from Journalists. I think that George W. Bush was perhaps ill-advised to take a question on who was the Prime Minister of India, which he failed to answer on the spur of the moment.
I am a politician, not a scientist, but as a politician I try to be aware of sources of information. If I were seeking an answer to your question, I might well enquire of Nils-Axel Mörner, whose work I have read and who seems to understand the issues.
The fact is that I simply don’t know why there is a large discrepancy between the trajectory of sea level based on satellite observations, and that based on direct measurements, though I note that it is discrepancies of this sort that engender doubts about some of the confident assertions of climate scientists.
If you want me to speculate, I will. I guess there may be some read-across from the similar discrepancies between mean global temperature figures based on ground stations and based on satellites. Ground stations don’t give anywhere near universal coverage, and those who manage the data are all too willing to interpolate. The available set of ground stations varies over time (many cold-climate stations were lost on the break-up of the USSR, for example). Moreover the immediate microclimate of individual ground-stations varies over time. You will be familiar with the research that finds that urban sprawl and air-conditioners and tarmac have influenced many ground stations. For these reasons I feel that the satellite data have more credibility.
The problems with local measurements of sea level are even more severe. Natural movements in the sea (waves and tides) are orders-of-magnitude greater than the couple of millimetres a year which you’re trying to measure. Local topography and local weather influence currents and sea level in all sorts of unpredictable ways.
Then of course you have the question of tectonic plate movement. We hear how sea level rise is affecting Bangladesh, but few people recall that the relevant tectonic plate is being subducted (under the India plate, if I remember), so the issue is less the sea rising than the land subsiding.
Nor should we ignore tectonic effects in the UK. The village of Dunwich disappeared under the North Sea centuries before the current slight warming – we can hardly blame that on anthropogenic emissions.
The big picture on sea level rise is that at the beginning of the current Interglacial, ten to twelve thousand years ago, there was very rapid glacial ice-melt which led to serious sea level rise – hundreds of feet in a few hundred years. This inundated the open country where the North Sea now is, and it created the English Channel. Since that time, the rate of rise has generally declined, and is now at a very low level indeed, which may be primarily an issue of thermal expansion.
It is interesting to reflect on the status of small islands and coral atolls, whose leaders will be in Paris shortly with their begging bowls, demanding climate reparations from Western countries. Do you believe that all these islands were exactly the same 400 feet (or so) above sea level in 10,000 BC, and that it’s just coincidental that they’re all a few feet above sea level now? Or do you recognise (as Darwin did) that coral atolls grow with sea level, and will always be roughly the same height above the surface?
Of course it is true that there is some melting of glaciers and ice caps, which might cause sea level rise (though the Arctic ice-cap is mostly floating, so will not add to sea level). But there is good geological evidence that glaciers advance in cool periods and retreat in warm periods (so far so obvious), and it seems overwhelmingly likely that the ice caps behave in the same way. As the world did not drown during the Minoan Optimum, or the Roman Optimum, or the Mediæval Warm Period, I feel very confident that it won’t drown in the current 21st Century Optimum.
And now, Professor Merrifield, you may pull your rabbit out of your hat and explain to a waiting world how you explain NASA’s discrepancy.