Daily Archives: 08/03/2012

Talking about the weather

Red sky at night, shepherd’s delight;
Red sky in the morning, shepherd’s warning.

No, I’ve no real idea what this means either – though I presume that it told generations of English shepherds whether to leave the sheep in the fields or bring them in to shelter.  Weather lore is a bit like that: a useful mnemonic for specific local purposes that doesn’t translate satisfactorily once you move to another place.

So what do you do when you do move to another place?

We’ve been having a lot of weather in Australia lately.  Towns from Roma to Forbes have been flooded, the rivers are running, and the 19th century myth of an inland sea sounds more plausible than usual.

We all now know that the reason for the wet weather is La Niña, El Niño’s soggy sister, but it is only in the last few decades that scientists have began to explain what Chilean fishermen have recognised in outline for hundreds of years.

The Southern Oscillation describes a pattern where the Pacific Ocean alternates between periods of warm and cool surface temperatures, which in turn affects air pressure and wind patterns across the Pacific – and perhaps well beyond.  During El Niño events it is dry in eastern Australia and wet on the American Pacific coast; the reverse occurs with La Niña.  Here in Australia we are currently being drowned by La Niña.

When European settlers arrived in Australia, they knew they had to learn about the local weather.  The governors were naval or military men, so they were used to keeping a meteorological record.  Over time, the new arrivals expected that this record of temperature, wind direction and rain, would give them a basis for predicting the weather – though weather forecasting in the late 18th century was still at the ‘red sky at night’ level of accuracy.

William Dawes journal

The meteorological journal of William Dawes, 1788

But they had no idea that they were dealing with a climate system that swings so dramatically, and so slowly, between wet and dry seasons.  Wikipedia suggests an oscillation of 5 years; the Australian Bureau of Meteorology suggests 3 to 8 years.  The truth is there is a great deal we still don’t know about the Southern Oscillation, but we do know it is highly variable.  It doesn’t tick regularly like a clock – or a pendulum.

The key figure in turning weather forecasting from an art to a science was Charles Darwin’s companion from the voyage of the Beagle, Captain (later Sir) Robert FitzRoy.  He did excellent survey work on the Beagle, received a gold medal from the Royal Geographical Society.  He was Governor of New Zealand from 1843-5, but was recalled for supporting the Maori against the settlers in their disputes over land.

Robert FitzRoy barometer

In 1854, FitzRoy was appointed head of the newly established meteorological department in the Board of Trade.  Using the weather logs he persuaded ships’ captains and colonial observers to send him, he gathered together information on the weather, and collated this enormous pile of information into charts of winds and currents.  He came up with the idea – and the name – of ‘synoptic charts’.  Acting on his hunch that falling air pressure predicted stormy weather, he distributed barometers to ports around Britain.  They became standard in Australia, too.  He wrote The Weather Book: A Manual of Practical Meteorology (1863), available on Google Books here.

FitzRoy was probably always a depressive.  He invited Charles Darwin to join him on the Beagle because he recognized the need for a companion to talk to during the voyage – and how fortunate was that for the development of science.  Despite his successes, the problem didn’t go away, and in April 1865, FitzRoy killed himself by cutting his throat with a razor.

FitzRoy introduced the idea of forecasting to meteorology, but he always recognized the limitations of forecasts:

Prophecies or predictions they are not: the term forecast is strictly applicable to such an opinion as is the result of a scientific combination and calculation, liable to be occasionally, though rarely, marred by [various unexpected events] not yet sufficiently indicated to our extremely limited sight and feeling.  We shall know more and more by degrees. (The Weather Book, p. 171)

Thanks to FitzRoy, ships’ captains and port authorities began to collect data on air pressure and sea temperature, as well as the established categories of rainfall, wind and air temperature.  Thanks to FitzRoy, that data is now being used to study the Southern Oscillation – and we shall know more and more by degrees.

Anita McConnell, ‘FitzRoy , Robert (1805–1865)’, Oxford Dictionary of National Biography, Oxford University Press, 2004; online edn, May 2009 [http://www.oxforddnb.com.ezproxy.library.uq.edu.au/view/article/9639, accessed 8 March 2012]
SEARCH: South Eastern Australian Recent Climate History