Space Sunshades: Time to ditch the sunscreen?

Tomorrow the skies will light up for the New Year’s celebrations across the globe. However, the backdrop to thousands of fireworks displays could look very different in the future if space geoengineering takes off. This is the most direct and technologically reliant SRM, working on the idea that a giant ‘shade’ or ‘mirror’ in space could reflect enough solar insolation to cool the planet quite quickly. It might sound quite drastic, but considering that Znamya 2 space mirror project (directing light towards Earth) launched successfully in the 90s, it appears technically feasible.

The second (failed) experiment of Znamya 2.5 (SRC, 1999). A geoengineering space mirror would be faced away from Earth and reduce solar insolation reaching the Earth.

How big?

Znamya 2 was 20m in diameter and produced a spot of light 5km in diameter. To cool the planet enough to reach the two degree target the space mirrors would need to cover an area of 3 million km² on Earth. This is approximately the size of India, but only 1/55 of the Pacific Ocean. Lior (2013) suggests that the space mirror technology is more likely to be developed for economic gain i.e. for harnessing solar energy and lighting up areas in need e.g. during natural disasters when nightfall hinders rescue efforts. However, this would require facing space mirrors towards the Earth and increasing solar radiation. Lior (2013) does not rule out the idea of turning the mirrors around for geoengineering purposes, but ultimately the geoengineering mirrors would have to offset the impact of the other space mirrors before reducing total solar insolation. This would require a larger area to be covered.

Where?

Space mirrors similar to Znamya, made from a fine (5 micrometre thick) reflective film, which burn up in the atmosphere on descent, may be the easiest to implement. This doesn’t mean it would be the most appropriate solution on such a large scale because they could interfere with existing satellites. Other suggestions include placing reflectors at the L1 point (see diagram) rather than in orbit. This would require huge technological advances, but reduces the direct effect on specific regions because the reduction in solar insolation would be global.

A) Angel (2006) and Caldeira (2013) B) Ecochunk (2012) C) University of Arizona (2006)

Moral Issues

The idea that geoengineering could result in reduced efforts to change our fossil fuel dependent lives is especially an issue for space mirrors. The negative consequences are more likely to result from a general change in the hydrological and biological system, which is not as direct as effects of other geoengineering methods. Morrow (2014) suggests that a reduction in emissions could be justified if geoengineering methods are successful. However, this would not be the case for SRM. Space mirrors would not reduce ocean acidification and any failure in the system could result in a more dramatic global warming effect, so reduced mitigation efforts could be catastrophic.

If the technology could be developed, I don’t think it’s the worse idea we have as a ‘back-up’ option. By no means is this a solution, but more of a way to buy time if warming reaches dangerous levels.