Climate change has triggered ideas for large scale engineering of global systems. Large-scale ‘technological fixes’ fall into two categories. Carbon dioxide removal (CDR) techniques are designed to extract CO2 from the atmosphere. Solar radiation management (SRM) techniques are intended to reflect a portion of the sun’s light back into space. CDR is based on biological, chemical or geological carbon sequestration. SRM is based on natural effects observed in the atmosphere following volcanic eruptions. A proposal for ‘sunshade’ geo-engineering consists of the installation of space-based sun shields, or reflective mirrors, to deflect a proportion of incoming solar radiation before it reaches the atmosphere. Sunlight deflectors would be placed in near-Earth orbits or near the Lagrange point, about 1.5 million kilometers above the planet, where the gravitational pull of Earth and the sun are equal. An array of sunshades in this position would pose less threat to orbiting satellites than would near-Earth objects (UNEP 2010b, the Economist 2010b). If anything, these proposals underline the severity of the situation as well as how little we really know. They also give new perspectives on power. As Andre Matthews, an anthropologist at the University of California puts it, it is not just a matter of constructing a switch, it is a matter of constructing a hand you trust to flip it (the Economist 2010b). We should also realise how little we understand and realise that the risks of such global large scale engineering are huge and totally unpredictable.
It is already a fact that we change many of the planet's systems enormously, but in the same way as most of these changes are a result of many small things (the car you drive, the meat you eat etc), also the solutions are to be found there rather than in macro engineering.
UNEP 2010b, UNEP Year Book 2010
The Economist 2010b, We all want to change the world, 3 April 2010