30 • Professional Engineering • 15 October 2008

ENVIRONMENT

Gordon Brown thought hehad the measure of our daysas he announced his bailoutfor the banks last week.

“Extraordinary times,” heannounced, “call for bold and far-reaching solutions.” The financialmeltdown has been so swift anddramatic that it’s managed to wipeclimate change off the agenda of themainstream media for a couple ofweeks. But climate concerns onlyadd, of course, to the apocalyptictone and many commentators saywe aren’t doing anything likeenough, or that anything we aredoing is far too little, way too late. Some commentators have

suggested we are eight years awayfrom a tipping point for CO2 levelsthat would herald irreversible,runaway climate change.Meanwhile, Jim Lovelock, thedistinguished scientist andalarmingly fatalistic proponent ofthe Gaia theory, said earlier thisyear that all we could do was tofocus on enjoying the next 20 yearswhile we had the chance; after thatpoint Britain would begin atransformation into a partiallysubmerged refuge for folk fleeingmainland Europe. Is it time for bold and far-

reaching solutions to reduce CO2levels, ones that sound fantasticalbut have deadly serious adherents?And if we can justify throwing £500billion at our banks, how aboutpumping £100 million intounderfunded but grandiose schemesto save the planet right now?That’s the level of investment that

Brian Launder, professor ofmechanical engineering at theUniversity of Manchester and fellowof the Royal Society, would like tosee devoted in the next Budget to“geo-engineering”, an umbrella termfor a group of bold and far-reachingactions that might, possibly,mitigate climate change. Not everyone is a fan of the

concept of geo-engineering. TheIntergovernmental Panel onClimate Change dismissed it as“speculative and unproven with therisk of unknown side effects” lastyear. Environmental groupsincluding Friends of the Earth andGreenpeace are suspicious of anyscience that could alter the Earth’sclimate with unknown effects andthat could divert attention andresources from existing strategies to

What’sthe bigidea?Geo-engineering – massiveprojects to alter nature – is theonly way left to fight climatechange, says a growing band of believers. Ben Hargreavesmeets scientists and thinkers whosay we must explore this moreradical – and risky – approach

Lights in the sky:

Only by tackling the

forces of nature can

the fight to clean up

the environment be

won, say exponents

of geo-engineering

15 October 2008 • Professional Engineering • 31

ENVIRONMENT

reduce CO2 emissions, such asrenewable power. But Launder says geo-

engineering – which includesconcepts such as brightening cloudsto reflect more sunlight, or placinggiant lenses in space to bend solarradiation around the Earth – shouldbe viewed as a pragmatic strategythat complements existing efforts toreduce emissions. And if the ideas seem loopy, they

are no crazier than our lifestylesnowadays, he says. “There’s a haemorrhaging of CO2

from the way lifestyles havechanged. People have more moneyand it’s taking that flight to the USfor your bachelor party, or wantingto be warm outside the pub in thewinter while you’re smoking so youget these patio heaters throwing outvast amounts of heat.“I just think the world is crazy,”

he adds, rather sadly. “And I cannotsee us getting CO2 emissions undercontrol. Every day one sees thatthings are more serious than we thought.”It is against this background that

Launder and Michael Thompson, ofthe Centre for Mathematical Sciencesat Cambridge University, have editeda recently published series of RoyalSociety Philosophical Transactions onthe “macro-engineering” optionpresented by various geo-engineeringschemes. “While such geo-scaleinterventions may be risky,” the twoauthors write, “the time may wellcome when they are accepted as lessrisky than doing nothing.”Environmentalists blanch at the

idea of spraying sulphur into theatmosphere to change the Earth’salbedo – the extent to which itdiffusely reflects light from the sun– because it would create more acidrain. “The delivery of sulphur to thestratosphere in a way that willproduce particles of the right size isshown to be a complex andpotentially very difficult task,” admitthe authors of the Royal Societypaper on the subject. But Launder says: “If the world is

facing extinction or half of theworld is becoming uninhabitableand [faces] enforced migration offour billion people, a bit of acid rainis a very small problem.”Perhaps another form of

modifying albedo is more palatable:British US-based atmosphericscientist John Latham and Stephen

Salter of the University ofEdinburgh have been workingtogether on a form of cloud seedingto alter the reflectivity ofstratocumulus. The principle wouldsee an increase in the dropletnumber concentration in maritime stratocumulus clouds,thus increasing their albedo forincoming sunlight, and their longevity. This would produce a cooling

effect, the magnitude of which, intheory, could be controlled. Theresearchers believe it could balancethe warming caused by increasedatmospheric CO2 concentrations.

The engineering hardwarerequired to make such a schemereality would include giant wind-driven spray ships out at sea. Theywould sail perpendicular to theprevailing wind and release micron-sized drops of seawater into theboundary layer beneathstratocumulus clouds. The 300-tonne ships described

by the Royal Society would bepowered by Flettner rotors ratherthan conventional sails, and woulddrag turbines resemblingpropellers through the water togenerate electrical energy. Thisenergy would be used to create

spray by pumping water throughbanks of filters and then to micro-nozzles with piezoelectricexcitation to vary drop diameter. Itis believed that a global albedoincrease of around 1.1% wouldprovide a sufficient offset of solarenergy to combat global warming. The Latham-Salter geo-

engineering concept, Launderbelieves, is the most “promisingscheme of all”. But there are others.One would involve seeding the seaitself with massive levels ofnutrients to encourage planktongrowth. Increased levels of planktonwould see more CO2 absorbed inthe sea, thereby sequestering agreater level of atmospheric carbon. But scientists admit there are

many unknowns, and it’s easy tosee why the thought of dumpingiron filings into the sea withunpredictable results does not findfavour with the green lobby. TheRoyal Society authors believemuch more work on such a schemeneeds to be carried out before itbecomes viable. They say: “Forocean fertilisation to become aviable option to sequester CO2, weneed more extensive and targetedfieldwork and better mathematicalmodels of ocean biogeochemicalprocesses. Models are needed bothto interpret field observations andto make reliable predictions about the side-effects of large-scale fertilisation.”Launder hopes these concepts

will be taken more seriously bygovernments. “If anything, Brown ismore serious than any of hisimmediate rivals [on climatechange],” he ventures. But intense scepticism must

remain over the ability of politiciansin different countries to cooperateand think globally – one of thetoughest requirements of thepotential deployment of a geo-engineering programme. Laundersays: “It’s research and developmentthat absolutely has to be done –though it’s odd in the sense that youhope never to use it. In that senseit’s analogous to the H-bomb.“It’s not a certainty, but there’s a

pretty good risk that if we don’t havegeo-engineering we’re going toprofoundly change the world we livein within a couple of generations.“I look at my grandchildren and

think: ‘My God, what sort of worldare they going to be inhabiting?’”

SUNSHADES IN SPACE AND MECHANICAL TREES

Not every geo-

engineering scheme made

it into the Royal Society

papers. Dr Klaus Lackner,

professor of geo-physics

at Columbia University’s

Department of Earth and

Environmental

Engineering in the US, was

invited to contribute an

article on mechanical

trees for CO2

sequestration, but was

too busy.

In Lackner’s concept,

which Prof Launder

believes is worth funding

but “unworkable”,

hundreds of thousands of

artificial trees capable of

absorbing CO2 would be

built. The synthetic trees

would act as filters, with

an absorbent coating

such as limewater on

their “leaves” seizing

carbon dioxide and

retaining the carbon. The

coating would need to be

changed frequently as it

would soon fill up with

CO2 and the trees would

need to be near

repositories for the

carbon-laden material.

Another idea that

didn’t make it into the

Philosophical Transactions

was developed by Roger

Angel, the director of the

Steward Observatory

Mirror Laboratory in

Arizona. It would see a

huge sunshade made out

of many trillions of small

discs orbiting the Earth at

an altitude of 1.5 million

km (known as the L1

Orbit). The discs would

divert some of the sun’s

rays, preventing them

from hitting the Earth and

warming the planet. It is

thought that a sun screen

that blocked 2% of

sunlight and reflected it

off into space could halt

global warming.

It would be enormously

expensive and impractical

to get the discs into space

and would take years to

launch them into orbit.

The shade might have a

diameter of 1,800km.

Nonetheless, Angel has

won a grant from Nasa to

research his idea further.

“Angel’s approach is so

way out there,” says

Launder. “It’s not

something that would be

in the first phase of geo-

engineering strategies,

appealing though it is.”