Play­ing God With the Cli­mate

Reader's Digest (India) - - Contents - CLIVE HAMIL­TON

Geo-engineering—sci­ence fic­tion or a re­al­is­tic hope for hu­man­ity’s fu­ture?

Man has up­set the bal­ance of the Earth’s cli­mate. Should sci­en­tists use tech­nol­ogy to change it back? High-pro­file aca­demic and so­cial critic Pro­fes­sor Clive Hamil­ton ex­am­ines the push to­wards geo­engi­neer­ing

In re­cent times sci­en­tists have watched with mount­ing alarm as carbon diox­ide con­cen­tra­tions—par­tic­u­larly boosted by ex­plo­sive growth in China—have in­creased re­lent­lessly. Just last year the World Bank warned that “we’re on track for a 4°C warmer world marked by ex­treme heat­waves, de­clin­ing global food stocks, loss of ecosys­tems and bio­di­ver­sity, and life-threat­en­ing sea level rise.”

Against this back­drop, sci­en­tists be­gan to talk about re­sponses to this po­ten­tial cli­mate emer­gency—and the idea of geo­engi­neer­ing was born.

More than 40 schemes have now been put for­ward, all of which would de­lib­er­ately in­ter­vene in our cli­mate sys­tem. And the idea is gain­ing trac­tion, with Bill Gates com­mit­ting sev­eral mil­lion dol­lars to fi­nance re­search into geo­engi­neer­ing and Richard Bran­son pro­mot­ing it as a re­sponse to cli­mate change. Even top oil com­pa­nies are qui­etly back­ing geo­engi­neer­ing stud­ies, in an­tic­i­pa­tion of a shift in the po­lit­i­cal land­scape.

So how can we engi­neer the cli­mate? From ma­nip­u­lat­ing the Earth’s cloud cover to chang­ing the ocean’s chem­i­cal com­po­si­tion to blan­ket­ing the planet with a layer of sun­light-re­flect­ing par­ti­cles, there are plenty of the­o­ries out there. Some are grand in con­cep­tion, some are pro­saic; some are purely spec­u­la­tive, some are all too fea­si­ble. But they all tell us some­thing in­ter­est­ing about how the Earth sys­tem works.

It would take decades be­fore we could dis­cover whether at­tempt­ing to engi­neer the cli­mate is glo­ri­ous en­ter­prise or ru­inous folly, but in the mean­time here’s a look at some of the sur­pris­ing pos­si­bil­i­ties be­ing sug­gested.

Re­dec­o­rate in white

As the sea ice in the Arc­tic melts, the Earth loses some of its re­flec­tiv­ity— white ice is re­placed by dark sea­wa­ter which ab­sorbs more heat. If a large area of the Earth’s sur­face could be whitened, then more of the sun’s warmth would be re­flected back into space rather than ab­sorbed. A num­ber of schemes have been pro­posed, in­clud­ing paint­ing roofs white, which is un­likely to make any sig­nif­i­cant dif­fer­ence glob­ally.

What might be help­ful, though, would be to cut down all of the forests in Siberia and Canada. While it is gen­er­ally be­lieved that more forests are a good thing be­cause trees ab­sorb carbon, bo­real (north­ern) forests have a down­side. Com­pared to the snow­cov­ered for­est floor be­neath, the trees are dark and ab­sorb more so­lar ra­di­a­tion. If they were felled the ex­posed ground would re­flect a sig­nif­i­cantly greater pro­por­tion of in­com­ing so­lar ra­di­a­tion and the Earth would there­fore be cooler.

But if such a sug­ges­tion ap­pears

ou­tra­geous, it is in part be­cause mat­ters are never so sim­ple in the Earth sys­tem. Warm­ing would cause snow on the de­nuded lands to melt, and the sit­u­a­tion would end up worse than be­fore the forests were cleared.

More promis­ingly per­haps, at least at a lo­cal scale, is the at­tempt to res­cue Peru­vian glaciers, whose dis­ap­pear­ance is de­priv­ing the ad­ja­cent grass­lands and their live­stock of their wa­ter sup­ply. Paint­ing the newly dark moun­tains with a white slurry of wa­ter, sand and lime keeps them cooler and al­lows ice to form; at least that is the hope. (The World Bank is fund­ing re­search.)

Put up a shield

Another idea is to re­duce so­lar ra­di­a­tion be­fore it gets to Earth. One pro­posal is to spray sul­phur diox­ide or sul­phuric acid into the up­per at­mos­phere to form tiny par­ti­cles that would re­flect an ex­tra 1 to 2% of in­com­ing so­lar ra­di­a­tion back into space, thereby cool­ing the planet.

The most likely de­liv­ery method is a fleet of cus­tom­ized high-fly­ing air­craft fit­ted with tanks and spray­ing equip­ment, al­though a hose sus­pended in the sky is also be­ing in­ves­ti­gated. In ef­fect, hu­mans would be in­stalling a ra­dia­tive shield be­tween the Earth and the sun, one that could be ad­justed by those who con­trol it to reg­u­late the tem­per­a­ture of the planet.

How ef­fec­tive would such a so­lar fil­ter be in sup­press­ing warm­ing? All the mod­els in­di­cate that if we re­duced the amount of sun­light reach­ing the planet, the Earth would in­deed cool fairly quickly and evenly, al­though with less ef­fect at the poles. The mod­els also show that rain­fall would be re­turned some way to­wards pre-warm­ing pat­terns. Cru­cially, the so­lar shield would do noth­ing to off­set the acid­i­fi­ca­tion of the oceans due to carbon emis­sions.

But other sci­en­tists ar­gue that the cli­mate sys­tem is so com­plex that it is im­pos­si­ble to draw any firm con­clu­sions about the ef­fects of such a rad­i­cal in­ter­ven­tion in the Earth sys­tem.

Other stud­ies in­di­cate that the

In­dian mon­soon could be se­ri­ously dis­rupted, af­fect­ing food sup­plies for up to two bil­lion peo­ple, al­though the dis­rup­tion may be less than in a sce­nario of warm­ing with­out the so­lar fil­ter.

One prob­lem with sul­phate aerosol spray­ing—de­scribed as the “killer ob­jec­tion” — is that we can only get a good idea of how it would work by fullscale im­ple­men­ta­tion. Even then we would need at least ten years of global cli­mate data be­fore we had enough in­for­ma­tion to sep­a­rate out the ef­fects of sul­phate aerosol spray­ing from nat­u­ral cli­mate vari­abil­ity and, in­deed, from the ef­fects of hu­man-in­duced cli­mate change. The lev­els of om­ni­science and om­nipo­tence re­quired to make it work re­ally would have us play­ing God.

To add to the risks, if af­ter ten years, when we ac­cu­mu­lated enough data to de­cide that our in­ter­ven­tion was not a good idea, it may be im­pos­si­ble to ter­mi­nate the so­lar shield.

Find a new or­bit

In 1993, the es­teemed jour­nal Cli­matic Change pub­lished a novel scheme by the In­dian physi­cist P.C. Jain to counter global warm­ing. Pro­fes­sor Jain be­gan by re­mind­ing us that the amount of so­lar ra­di­a­tion reach­ing the earth varies in in­verse square to the dis­tance of the Earth from the sun. He there­fore pro­posed that the ef­fects of global warm­ing could be coun­tered by in­creas­ing the ra­dius of the Earth’s or­bit around the sun—a sci-fi style idea that uses nu­clear fu­sion. An

or­bital ex­pan­sion of 1 to 2% would do it, al­though one of the side ef­fects would be to add 5.5 days to each year. He then cal­cu­lated how much en­ergy would be needed to bring about such a shift in the Earth’s ce­les­tial or­bit. The an­swer is more than the amount of en­ergy hu­mans would con­sume over 100 bil­lion bil­lion years (the age of the universe is around 14 bil­lion years).

Sink the cul­prits

When we dig up and burn fos­sil carbon we make use of its trapped en­ergy; but the carbon atoms do not dis­ap­pear. So where do they go? First they go into the at­mos­phere. Some are then soaked up by veg­e­ta­tion. Some sooner or later end up in the var­i­ous lay­ers of the oceans. The deep ocean has the ca­pac­ity to ab­sorb large amounts of carbon diox­ide from the at­mos­phere, and it would help if we could get more carbon down there and hope that it stays.

But how do we get carbon to the deep ocean? The an­swer lies in what is known as the bi­o­log­i­cal pump. Tiny ma­rine plants known as phy­to­plank­ton grow by com­bin­ing carbon diox­ide, var­i­ous min­er­als and sun­light to mul­ti­ply into blooms. On death, grav­ity causes the plank­ton to sink.

The ef­fec­tive­ness of the bi­o­log­i­cal pump de­pends on the suit­abil­ity of con­di­tions for ma­rine life, in­clud­ing the avail­abil­ity of mi­cronu­tri­ents, es­pe­cially iron. If a short­age of iron is lim­it­ing plank­ton growth in an area of ocean, then per­haps the ar­ti­fi­cial ad­di­tion of the miss­ing in­gre­di­ent can stim­u­late al­gal blooms.

Fer­til­iz­ing some ar­eas of ocean with iron slurry does in­deed in­duce al­gal blooms. But it turns out that much of the carbon fixed in the phy­to­plank­ton does not find its way to the ocean floor but cir­cu­lates in the sur­face waters, feed­ing the food chain, be­fore be­ing emit­ted as carbon diox­ide back into the at­mos­phere.

And while iron fer­til­iza­tion stim­u­lates bi­o­log­i­cal pro­duc­tiv­ity in one area, nu­tri­ent steal­ing can see it fall in oth­ers. As one ex­pert said: “You might make some of the ocean greener by iron en­rich­ment, but you’re go­ing to make a lot of the ocean bluer.”

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