Weather Forecasts, and What We Now Know in the BBC’s Superb “Orbit: Earth’s Extraordinary Journey”.

Orbit: Earth's extraordinary journeyLast autumn, Kate Hum­ble pre­sent­ed a one-off pro­gramme on BBC2 called Will It Snow? The ques­tion it asked was, is it pos­si­ble to make long-range weath­er fore­casts? And the answer was an emphat­ic No.

Weath­er pat­terns are sub­ject to what chaos the­o­ry dubbed the but­ter­fly effect. A but­ter­fly beats its wings off the coast of Tokyo and six months lat­er there’s a hur­ri­cane in Florida.

The prob­lem is, every time you try to make a set of pre­dic­tions you need to fac­tor in about a dozen vari­ables. If any one of those vari­ables behaves slight­ly dif­fer­ent­ly than expect­ed, then that will have a knock-on effect on half a dozen oth­er variables.

And each of those will affect half a dozen oth­er vari­ables, each. Any num­ber of which will even­tu­al­ly come back to rad­i­cal­ly affect many of those orig­i­nal vari­ables a few weeks or months later.

Any mid to long-range pre­dic­tions there­fore will have been ren­dered com­plete­ly use­less. And that’s assum­ing there’s only a slight vari­a­tion in one of the orig­i­nal twelve. Invari­ably, there are innu­mer­able small vari­a­tions across the board.

So whilst it is pos­si­ble to make accu­rate pre­dic­tions over a four or five day peri­od, because you can allow for those slight vari­a­tions, over any­thing more than a few weeks those small changes will come to have huge and com­plete­ly unpre­dictable ramifications.

This top­ic was treat­ed in a much more mea­sured way when Hum­ble teamed up with Helen Czer­s­ki for their three part series, Orbit: Earth­’s Extra­or­di­nary Jour­ney. Dur­ing which, they fol­lowed our plan­et as it made one of its annu­al orbits around the Sun.

Using var­i­ous exot­ic loca­tions across the globe to illus­trate the dif­fer­ent phe­nom­e­na they were explor­ing, they com­bined exact­ly the right mix of glossy, trav­el­ogue loca­tions and fas­ci­nat­ing, sober sci­en­tif­ic explanations.

We learnt and were shown how the Earth­’s tilt is respon­si­ble for the annu­al sea­sons, and dis­cov­ered how it, the tilt, is one of three ele­ments that deter­mine when and why our plan­et expe­ri­ences spo­radic Ice Ages. Cru­cial­ly, they kept the sci­ence acces­si­ble with­out in any way becom­ing patronizing.

For not with­stand­ing our inabil­i­ty to ever be in a posi­tion to make long-range weath­er fore­casts, for the first time in our his­to­ry we can pro­vide a sci­en­tif­ic expla­na­tion for a huge range of the weath­er phe­nom­e­na that gov­ern life on this planet.

Though the Earth­’s tilt has long been guessed at, it is only now that we under­stand defin­i­tive­ly that it has a 41,000 year cycle, dur­ing which it moves from an angle of 24.5 degrees to 22 and back again, and that cur­rent­ly it’s at 23.5°. Like­wise, whilst tor­na­does and mon­soons have long since been mar­veled at, today we can pro­vide a sci­en­tif­ic expla­na­tion as to how and why they take place. And although we’re nev­er going to able to say exact­ly when and where they are going to hap­pen, dis­cov­er­ing what we can and can’t pre­dict is the most valu­able gift of all that sci­ence had giv­en us.

Once again, the BBC took us on a guid­ed tour of what we now know, and how it is that we know it. It’s an area they’ve become increas­ing­ly impres­sive in, and there’s a dis­tinct sense that, as far as sci­en­tif­ic pro­grammes on tele­vi­sion are con­cerned, we’re liv­ing in some­thing of a gold­en era.

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