Very old weather.

Edmond Halley is best known for his comet, but he was one of the great polymaths – as well as making astronomical discoveries he was also a notable meteorologist: he did important early work understanding the trade winds and monsoons. It’s less well known that that he was also a Naval Officer: in 1699 he was granted a commission as captain in the Royal Navy, and he commanded HMS Paramour (a pink) on an expedition into the South Atlantic to investigate the variation of the compass.

His main concern was with magnetism, but as a man of wide interests, Halley took with him examples of those two exciting modern scientific instruments: the thermometer and the barometer. I can’t find the logbook of the voyage, but Halley’s notes have survived: they were published by Alexander Dalyrmple, in 1775, as part of “A collection of voyages chiefly in the Southern Atlantick Ocean“. They date from 220 years before the logbooks we’re used to in OldWeather, but to anyone who’s looked at our logbooks they are oddly familiar: records of latitude, longitude, wind force and direction and, in the left-hand margin, thermometer and barometer readings.

In 1699 the barometer had been around for more than 50 years, and the barometer records in Halley’s account are clearly in the familiar inches of mercury. But the thermometer did not become a reliable, precision instrument until about 1725, when Fahrenheit invented the mercury thermometer with a standardized, calibrated scale. So when Halley says the temperature is ’33’ it’s not immediately obvious how this should be interpreted. Careful scholarship has established, however, that Halley was using a thermometer designed by Robert Hooke, and lavishly described in his book Micrographia:

The Stems I use for them are very thick, straight, and even Pipes of Glass […] above four feet long […] [filled] with the best rectified Spirit of Wine highly tinged with the lovely colour of Cocheneel, which I deepen the more by pouring some drops of common Spirit of Urine, which must not be too well rectified, […]

From Hooke’s description we can convert Halley’s reported units into modern equivalents at least approximately – Halley’s ’33’ was about 8°C.

The diary entries are mostly routine accounts of the movements of the ship, but occasionally he puts in longer and more interesting reports: here’s an example from Thursday 1st February 1700, when they were close to South Georgia, in the cold waters of the Southern Ocean:

[…] between 4 and 5 we were fair by three Islands as they then appeared; being all flat on the top, and covered with Snow milk white, with perpendicular Cliffs all round them […] The great height of them made us conclude them land, but there was no-appearance of any tree or green thing on them, but the Cliffs as well as the tops were very white, our people called A by the name of Beachy-Head, which it resembled in form and colour. And the Island B in all respects was very like the land of the North-foreland in Kent, and was at least as high and not less than 5 miles in front, […]

The following day they were disconcerted to discover that these ‘islands’ had moved, and fled north to warmer waters. This is the first recorded sighting of a tabular iceberg.

Halley’s observations are probably not of great value to climate scientists: his instruments were state-of-the-art for 1699, but it took decades longer for such observations to became accurate and plentiful enough for climate reconstructions. He did set a precedent though – possibly as the first person to go to sea with a barometer and a thermometer – and we’re still following his example more than 300 years later.

7 responses to “Very old weather.”

  1. Spencer Bliven says :

    Very interesting! I’m curious about the assumptions you made in converting temperature units. I assume ‘Spirit of Wine’ refers to some form of distilled alcohol? Did you have to make any other corrections based on the glass diameter, etc?

    I hope Halley’s logbooks get digitized. I would love to see a graph & map of his journey.

  2. Yvan Dutil says :

    I am curious how deep in time we could go. From what I read, weather reconstruction could be carried up to 1800 in the North hemisphere and 1900 in the Southern one. I am under the impression that some useful climatic data could be extracted as far a 1750. Local weather map could be created in central Europe around that period.

    • Philip says :

      I’m also curious about that – it depends how many observations we find, and how many we can recover. At the moment to say we can go to 1900 over much of the globe, and further in smaller regions looks like a sensible estimate. It does depend, of course, on what we are reconstructing: for daily weather it’s going to be hard to go back before 1800 except in small regions, but for less ambitions reconstructions (say of mean annual temperature) we can use a wider range of observational records and go further back.

  3. Yvan Dutil says :

    Phillip. I got that info from the 20CR paper:”Strictly speaking, the first retrospective analyses (i.e. reanalyses) were generated in 1819, when Brandes followed up on his original proposal and constructed 365 daily maps of pressure contours using barometric pressure observations taken in 1783 at several European stations”

    Hopefully, we have now access to more data and certainly better assimilation method. Can addition of wind speed in assimilation (which seams to improve them) and ground temperature push the horizon further in time, this is an exciting question.

  4. Yvan Dutil says :

    By the way, I would like to had that Halley was not a comet spotter. He was the first astronomer to calculate the periodic return of a comet. Actually, he died before the predicted return of the comet bearing his name.

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