Hu­man­ity ought to wise up on the long-term risks

Focus-Science and Technology - - Discoveries - Robert Matthews is vis­it­ing pro­fes­sor of science at As­ton Uni­ver­sity, Birm­ing­ham.

What would you think if a nu­clear-tipped mis­sile zoomed through space and nearly hit a satel­lite or two? That’s pretty close to what ac­tu­ally hap­pened on 12 Oc­to­ber this year – ex­cept that the ‘mis­sile’ was un­der no one’s con­trol.

Trav­el­ling at over 25,000 km/h, the hous­e­sized chunk of rock known as as­ter­oid 2012 TC4 packed the punch of a few dozen atomic bombs as it flew over­head, at a sim­i­lar al­ti­tude to many com­mu­ni­ca­tions satel­lites. Yet af­ter a bit of me­dia cov­er­age, the event soon went the way of all such ‘cos­mic close shave’ sto­ries, and dis­ap­peared off the news radar en­tirely.

Even when one of these ob­jects ac­tu­ally does make it through the at­mos­phere – as one did over Chelyabinsk, Rus­sia in 2013, in­jur­ing over 1,000 peo­ple – we all soon for­get about it. But are we be­ing too com­pla­cent? Many sci­en­tists ar­gue that we are, and they claim to have ev­i­dence to prove it.

The trou­ble is, that ev­i­dence isn’t very com­pelling. Ex­hibit A is that the chances of dy­ing in an as­ter­oid im­pact that trashes the planet are around 1 in 75,000 – that’s dou­ble the risk of be­ing killed by light­ning. But wait, that can’t be right, surely? Af­ter all, the last time the Earth got to­talled was around 65 mil­lion years ago, when the di­nosaurs were wiped out.

The ex­pla­na­tion lies in the fact that this risk de­pends on more than just how fre­quent the event is. While mas­sive as­ter­oid im­pacts are far rarer than light­ning strikes, the likely death toll is mil­lions of times higher – lead­ing to that sur­pris­ingly high fi­nal risk fig­ure.

Mul­ti­ply­ing the fre­quency of the event by its con­se­quences has long been deemed the only sci­en­tific way to make de­ci­sions about risk – and the the­ory be­hind this is pretty solid. But as a way of get­ting peo­ple – and politi­cians – to take risks of nat­u­ral dis­as­ters se­ri­ously, it doesn’t re­ally work. That’s be­cause the for­mula is only re­ally help­ful for de­cid­ing how best to pro­tect the whole of hu­man­ity for the rest of eter­nity. But Joe Pub­lic – and es­pe­cially Sir Joseph Politi­cian – tend to have rather more short-term con­cerns, such as liv­ing long enough to see their kids grow up, or get­ting re-elected. For them, that is per­fectly ra­tio­nal, too. So telling them they’re wrong to ig­nore risks on timescales so vast they’ll prob­a­bly never ex­pe­ri­ence them isn’t go­ing to win them over. Cos­mic catas­tro­phes, which typ­i­cally have timescales of cen­turies and more, run straight into this timescale prob­lem – which is prob­a­bly why few peo­ple out­side academia worry about them. But nat­u­ral dis­as­ters on much shorter timescales can still en­gen­der in­dif­fer­ence. From Cal­i­for­nia’s San An­dreas fault to the slopes of Mount Ve­su­vius, it’s clear that mil­lions of peo­ple are quite ca­pa­ble of pon­der­ing the risks of liv­ing on the sites of far more fre­quent nat­u­ral catas­tro­phes and de­cid­ing they’ll prob­a­bly be okay. So what kind of timescale do peo­ple take se­ri­ously when as­sess­ing such risks? Judg­ing by the re­sponse of those liv­ing in hur­ri­cane zones, it takes less than a gen­er­a­tion – around 20 years or so – for peo­ple to park their con­cerns about a re­peat of a pre­vi­ous dis­as­ter. That’s far shorter than the av­er­age ‘re­turn pe­riod’ of most forms of nat­u­ral dis­as­ter, such as earth­quakes, vol­canic erup­tions or Cat­e­gory 5 hur­ri­canes. In one sense, all of this bears wit­ness to the as­ton­ish­ing re­silience of the hu­man spirit. But it also high­lights a crit­i­cal limit to hu­man ra­tio­nal­ity – and a ma­jor chal­lenge to those seek­ing to pro­tect hu­man­ity from long-term dis­as­ter. Un­less they can find some way of cir­cum­vent­ing the timescale prob­lem, their pleas for ac­tion are likely to be greeted by the clas­sic re­sponse of each new gen­er­a­tion to the dire warn­ings of their el­ders: “Yeah, what­ever…”.


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