FGV-SP Administração 2014/1

NO HURRICANE TONIGHT

By Philip Ball

1 Isn’t it strange how we like to regard weather forecasting as a uniquely incompetent science—as

though this subject of vital economic and social importance can attract only the most inept researchers,

armed with bungling, bogus theories?

2 That joke, however, is becoming less funny. With Britain’s, and probably the world’s, weather

becoming more variable and prone to extremes, an inaccurate forecast risks more than a wet garden

party, potentially leaving us unprepared for life-threatening floods or ruined harvests.

3 Perhaps this new need to take forecasting seriously will eventually win it the respect it deserves.

Part of the reason we love to highlight the disastrously misplaced reassurance from Michael Fish, the

BBC’s TV weatherman, is that there has been no comparable failure since. “Earlier today,” said Fish,

“apparently, a woman phoned the BBC and said she heard there was a hurricane on the way; well, if

you’re watching, don’t worry – there isn’t.” Hours later, the great storm of 1987 struck. As meteorologists

and applied mathematicians Ian Roulstone and John Norbury point out in their account of the maths of

weather prediction, Invisible in the Storm, the five-day forecast is, at least in western Europe, now more

reliable than the three-day forecast was when the 1987 storm raged. There has been a steady

improvement in accuracy over this period and, popular wisdom to the contrary, prediction has long been

far superior to simply assuming that tomorrow´s weather will be the same as today’s.

4 Weather forecasting is hard not in the way that fundamental physics is hard. It’s not that the

ideas are so confusing, but that the basic equations are extremely tough to solve, and that hiding within

them is a barrier to prediction that must defeat even the most profound mind. Weather is intrinsically

unknowable more than two weeks ahead, because it is an example of a chaotic system, in which

imperceptible differences in two initial states can blossom into grossly different eventual outcomes.

Indeed, it was the work of the American meteorologist Edward Lorenz in the 1960s, using a set of highly

simplified equations to determine patterns of atmospheric convection, that first alerted the scientific

community to the notion of chaos: the inevitable divergence of all but identical initial states as they

evolve over time.

5 It’s not obvious that weather should be susceptible to mathematical analysis in the first place.

Wind and rain and blazing heat seem subject to caprice, and it’s no wonder they were long considered a

matter of divine providence.

Adapted from Prospect, February, 2013