Airborne Sunshade #
Reflecting a proportion of the sun’s energy away from the Earth is the most straightforward approach to cooling the planet, that absolutely know we would work; if we can do it.
One approach that has been mooted for a while, is placing mirrors or diffractors directly between the sun and the Earth; i.e. a “space sunshade” or “Planetary Sunshade”.
A space sunshade would help cool the Earth, but it would be extremely challenging, costly and time-consuming to build. For example, the Planetary Sunshade Foundation FAQ says cooling the Earth by 1°C would require launching a mass “at least 100,000 times as much as the ISS”.
We believe an airborne sunshade would be quicker, cheaper & more targeted then a space sunshade. It could have a significant role to play as an interim solution for the most urgent climate problems, such as in the Arctic.
The following table summarises how the space and airborne sunshades compare:
| Space Sunshade | Airborne Sunshade | |
|---|---|---|
| Position | L1 Lagrange point | Lower stratosphere |
| Altitude | 1,500,000 km | 10 km - 20 km |
| Cost | $ trillions | $ billions |
| Coverage | global | targeted |
| Impact | constant | controllable |
| Current Tech? | No | Yes |
| Timescale | ~30+ years | ~10 years |
Targeted & Safe #
SkyScroll was designed both as alternative or a complement to the most well-known approaches to global engineering, i.e. Stratospheric Aerosol Injection (SAI).
SAI is potentially a relatively cost-effective solution to cooling the Earth as a whole, but it has many challenges and has been dogged by controversy.
One key problem is that it is very difficult to target the effects of SAI. Model experiments indicate doing stratospheric aerosol injection at the poles may help localise impacts, but there is always a global impact.
SkyScroll is completely targetable geoengineering tool, with no obvious negative side effects. SkyScroll was specifically designed to play a major role in the urgent and radical goal of refreezing the Arctic.
A Moral Hazard? #
Many argue geoengineering is dangerous path to go down, and a “moral hazard”, because the prospect could be used by some to disincentive reductions in greenhouse gas emissions. These are rational concerns.
However, in weighing up the pros and cons, it is also necessary to consider the precautionary principle and the “moral hazard of non-research”.
It is extremely important that no geoengineering proposal should any way be used as justification for not cutting greenhouse gas emissions urgently and deeply. No one we know in the field thinks of it that way.
Evidence indicates there are some critical parts of the climate urgency which cannot now be addressed by emissions reductions alone, in particular the situation in the Arctic. Therefore, there is no inherent moral hazard in solutions specifically targetting the Arctic.