3.1 Field experiments in SRM
The first field experiments intended specifically to inform Solar Radiation Management (SRM) were those led by prominent Russian scientist Yuri Izrael (1930–2014) in 2008.
These sprayed smoke in the air by burning, essentially, firework flares from a helicopter at up to 200 m height and by burning petroleum from a car at ground level (Izrael et al., 2009) (Figure 5a). The scientists then measured how much the resulting clouds of smoke blocked the sun. Experiments continued over the next couple of years (Izrael et al., 2011).
So far this has been the extent of SRM field experiments. In the UK, the 2011 Stratospheric Particle Injection for Climate Engineering (SPICE) project, designed to spray two bathfuls of water as fine droplets at 1 km height from a hose tethered to a helium-filled balloon (Figure 5b), was cancelled for a variety of reasons. Other geoengineering field experiments with sulfates or sea salt have been considered, but have not yet been carried out (Keith et al., 2014).