CORRESPONDENCE

Engineer solar solutions locally to save water

Solar radiation management is good for more than just global geoengineering (see also A. A. Rahman et al. Nature 556, 22–24; 2018). At the local level, the brightening of urban surfaces has helped to cool cities since the sixth century bc in Athens, and the same physics that causes aerosols to brighten the stratosphere (Mie theory) can also make water more reflective.

Dissolving air in water to generate bright, part-per-million dispersions of reflective microbubbles can curb evaporation by reducing solar warming (R. Seitz Clim. Change 105, 365–381; 2011).

Aside from cooling urban reservoirs, this water-conservation technique allows farmers who cannot afford reservoir covers to reduce crop losses from drought.

I suggest that some of the money spent on arguing about global governance of geoengineering could be better used to develop local water-conservation technologies.

Nature 557, 309 (2018)

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