Reducing the Effects of Climate Change
Reducing the Effects of Climate Change
Daniel Frost reports on the increasingly ambitious geo-engineering projects being explored by scientists
A
ABecause the world leans so heavily on fossil fuels, and because so much carbon dioxide has already entered the atmosphere, a large number of specialists now treat serious global warming as unavoidable. Holding it to a manageable level is, in their view, the most that can realistically be achieved, and for the moment the one credible way of doing so is to reduce the carbon we emit. Yet only a handful of nations are advancing quickly here; for most, merely slowing the rate at which emissions climb — never mind cutting them back — is proving hard. That difficulty explains why a growing body of researchers has turned to geo-engineering, the deliberate reshaping of the environment on a vast scale. Its supporters liken it to a standby generator: should Plan A, weaning ourselves off fossil fuels, break down, a Plan B is needed — large-scale interventions designed to slow global warming or turn it back.
B
BOn a small, local scale, geo-engineering has already proved its worth. Over many decades the state parades held in Verkhov have gone ahead beneath cloudless skies, after aircraft seeded the clouds above with dry ice, silver iodide and cement powder to break them up. A good many of the schemes now on the table aim at the reverse effect — cutting the quantity of sunlight that reaches the planet. Boldest of them all is the proposal of Professor Viktor Halloran of the University of Ashford, who would launch as many as sixteen trillion tiny craft, each no heavier than a gram, into an orbit 1.5 million kilometres out, where together they would act as a transparent, light-bending screen. By Halloran's calculation, such a device could trim the light arriving at the Earth by two per cent.
C
CMost of the geo-engineering trials undertaken up to now — among them the planting of forests across deserts, and the scattering of nutrients over the sea to trigger blooms of plankton — have aimed at cooling the Earth as a whole. A handful, though, are directed specifically at halting the thaw at the poles, the Arctic above all. Their logic runs like this: build the ice sheets and frozen seas of the far north back up, and a greater share of the sunlight will be thrown back into space, which in turn eases the warming of both ocean and air.
D
DSeveral researchers have floated the notion of spraying aerosols into the stratosphere over the Arctic. Sulphur or hydrogen-sulphide aerosols would be used, the resulting sulphur dioxide forming a reflective haze that dims the incoming light worldwide. Nature supplies the model: great volcanic eruptions, Mount Pinatubo in the Philippines in 1991 among them, cooled the globe briefly by half a degree Celsius. A different line of enquiry has examined whether Greenland's ice sheets might be held in place by strong reinforced chains, so that icebergs are stopped from slipping out to sea. In the Russian Arctic, meanwhile, one plan calls for millions of birch trees to be planted. The evergreen pines native to the area shade the snow and soak up radiation; birches, by contrast, drop their leaves once winter comes, and the bare canopy lets the snow throw the radiation back. Diverting the great northern waterways to push more cold water toward the places where ice forms is another option some climate scientists put forward.
E
EBut are such schemes ever likely to be put into practice? As a rule, the people most wary of geo-engineering are the very researchers conducting the work. Halloran insists that his own project is 'no replacement for building up renewable energy, which is the only lasting answer'. Dr Simone Vance, of the Coastal Atmospheric Laboratory, is just as reserved about what geo-engineering can offer: 'I think we would all accept that if we switched geo-engineering off one day, the planet would slide back to the state it was in beforehand very quickly — most likely inside ten to twenty years. That is genuinely a cause for concern.'
F
FResearchers at the National Institute for Climate Modelling have already warned that injecting sulphur into the atmosphere could disturb rainfall across the tropics and the Southern Ocean. 'Schemes that put aerosols into the stratosphere, or that seed clouds, would indeed cool the planet and widen the reach of the sea ice,' Vance notes, 'but every model we run points to some change in how precipitation is distributed.'
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GAccording to Dr Theo Brandt of the University of Kelmore's School of Earth Systems, who has modelled how the screen and aerosol proposals would each affect the climate, another danger is that a project may 'overshoot'. 'You might well pull global temperatures back down to pre-industrial figures, and yet the poles could stay warmer than they ought to be while the tropics end up cooler than they were before industrialisation.' Steering clear of that outcome, Brandt explains, would mean running Halloran's screen at only half its capacity — which for him simply underlines the argument that the wiser course is to remove the need for geo-engineering in the first place.
H
HWhat draws so much of the scientific community to geo-engineering is, above all, a lack of confidence that politicians will ever agree on the carbon cuts that are required — and then actually enact them. Even prominent conservation bodies acknowledge that the potential of geo-engineering is worth looking into. As Dr Anya Sorensen, climate-change adviser to the Global Wildlife Trust's Polar Programme, puts it, 'Climate change driven by human activity has left us at a point where it would be wrong to rule out thinking this subject, and everything it might offer, right through.'
Question 1 - 3
Which paragraph contains the following information?
1
an explanation of how rebuilding polar ice could lower the temperature of the oceans
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B
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G
H
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