Geoengineering: Implicit promises

A geoengineering experiment has come unstuck. But there will be more

FOR the past few years, a European collaboration called IMPLICC (Implications and Risks of Novel Options to Limit Climate Change) has been looking at what it might mean to engineer the climate, by reducing the amount of sunshine that reaches the Earth’s surface. A lot of IMPLICC’s work, like much else in climate science, has taken the form of computer modelling. In its case the models try to mimic the effects of things like putting veils of reflective particles into the stratosphere, or brightening the clouds over the oceans.

This week the IMPLICC team and other interested parties met in Mainz, Germany, to discuss the results—for the various models have turned out to agree far better than many of their creators expected. In particular, they suggest that particles in the stratosphere can indeed stop rising levels of greenhouse gases raising the overall global temperature, though in doing so they slightly cool the tropics while the poles warm a bit. Other things being equal, the models also agree that geoengineering tends to suppress the hydrologic cycle, with less evaporation and less rainfall.

Some researchers, however, want to go beyond modelling. They wish to experiment in the real world. The highest-profile of these schemes has been part of a programme called SPICE (Stratospheric Particle Injection for Climate Engineering), which is paid for mainly by Britain’s Engineering and Physical Sciences Research Council (EPSRC). Much of SPICE takes place in computers and laboratories, but one part was to be an actual experiment—a tethered balloon with a kilometre-long hosepipe attached to it. The idea was to pump a small amount of water up to the balloon and thence out into the air, so as to assess the possibility of spraying out other substances at far greater heights.

This move to a practical project has proved controversial. Some people worry that tinkering deliberately with the atmosphere may cause more harm than good. Others fear that if geoengineering is shown to work it will, by offering a palliative for the problem of global warming, let politicians put off difficult decisions that might lead to a permanent solution. As Clive Hamilton, a philosopher critical of much of the thinking behind geoengineering research, pointed out to the meeting, though the environmental effects of such experiments may be nugatory, their effects on the way people think could be more profound, and much less easily contained.