Imagine this frightening, but plausible, scenario. Sometime in the next twenty or thirty years CO2 levels in the atmosphere have reached 450 ppm and triggered runaway global warming. The Greenland ice sheets are melting, sea levels are rising rapidly, and millions of the earth’s population are in peril. Even if CO2 emissions fell to zero, the accumulated CO2 in the atmosphere would continue to drive temperatures upwards. What do we do then?
One answer is geo-engineering – combating the effects of climate change without actually reducing emissions.
We know it works
The most popular approach would be to inject sulphur into the atmosphere, mimicking the effects of volcanic eruptions which block out the sunlight and so reduce global temperatures. Ten kilogramme of sulphur could offset the warming effects of a million tonnes of carbon dioxide. You could get it into the atmosphere by balloon, from military air-to-air refuelling aircraft, or even by adding it to conventional aircraft fuel.
If you don’t like the idea of adding more gunk into the atmosphere, how about launching millions of tiny mirrors into space, and having them reflect some of the sun’s light directly away from earth? Much more expensive, but somehow more environmentally friendly.
Alternatively, how about encouraging the growth of CO2 absorbing plankton in the world’s oceans, by feeding them more iron?
None of these methods is currently feasible, for ethical, political and financial reasons, but in a few decades time we might be more desperate. Watch this space.