From Eric Kvaalen
It is true that the impact of limiting our production of carbon dioxide will be small and slow (9 November, p19). Even if we were to stop all CO2 production, it would take more than a hundred years for the atmospheric CO2 to return to pre-industrial levels. During that time, the icecaps will begin to melt and the oceans will rise.
But there are probably cheaper ways to counter global warming than building vast structures in space. For instance, it might be possible, at an affordable cost, to cover a few million square kilometres of ocean with white floats to reflect sunlight back into space. This would be cheaper than a Fresnel lens in space of the same size.
And even though solar radiation is stronger in space, it would be cheaper to put vast arrays of solar panels in deserts than to make them in space together with the means of transmitting the energy to Earth.
Paris, France
