Why a space sunshade isn't such a bright idea

There is a fundamental contradiction between two of Vaclav Smil's innovations to save humanity [New Scientist 7 January 2023, p.38]. He calls for more efficient photosynthesis, while also suggesting the need for a planetary sunshade to control global warming.

However such geoengineering would not only cool the earth, but also reduce the efficiency of photosynthesis at the global level. We are already destroying much of the photosynthetic capacity of the planet through deforestation, land use change and impacts on ocean phytoplankton.

A tipping point where the energy captured by photosynthesis is no longer sufficient to support all life may be closer than we think.

Download this letter as a pdf.

See also my blog on risks to photosynthesis.