Can a Sun Umbrella in Space Save Our Planet from Climate Change?

Scientists have plenty of ideas to prevent climate change and its devasting consequences. They termed this large-scale intervention of the Earth’s natural system as geoengineering, and the techniques to counteract climate change are grouped into two main categories – solar radiation management (SRM) and greenhouse gas removal (GGR).

The latest bold idea to combat the devastating effects of climate change comes from an astronomer at the University of Hawaiʻi Institute for Astronomy, István Szapudi.

He proposes to place a giant sun umbrella tens of thousands of kilometres above the Earth’s surface to block its harmful UV rays and cool the Earth tethered to a captured asteroid as a counterweight.

Szapudi published his paper, “Solar radiation management with a tethered sun shield,” in the Proceedings of the National Academy of Sciences (PNAS) journal.

The idea of a solar shield has been introduced previously. However, the necessary weight of the shield, one that could balance the gravitational forces and prevent solar radiation pressure from blowing it away, makes the lightest materials prohibitively expensive.

Szapudi argued that despite the cost and challenges associated with this feat, it is still worth attempting due to the severity of the problem, and modifying the Earth’s atmosphere by other SRM methods, such as spraying sulphur in the stratosphere, could be riskier. Hence, he reckons that focusing on space-based SRM strategies presents less risk.

He proposed two innovations – a counterweight tethered to the massive shield and an asteroid that would serve as the counterweight that would gradually fill with lunar dust or asteroid material that would act as ballast and avoid launching most of the mass from Earth.

The proposed shield would only weigh around 35,000 metric tonnes or 1% of the weight, while the asteroid acting as ballast would achieve the rest of the mass, approximately 3.5 million tons. Graphene, a lightweight and robust material, will make both shield and counterweight.

The strategy involves launching the counterweight into space and tethering it to the solar shield. The weight reduction will make the plan plausible, reducing costs and simplifying the implementation process. Rockets today can only lift around 50 tons into low Earth orbit.

Through his sun umbrella project, Szapudi aims to reduce solar radiation by 1.7%, which he believes is sufficient to prevent the devasting effects of climate change.

“In Hawaiʻi, many use an umbrella to block the sunlight as they walk about during the day. I was thinking, could we do the same for Earth and thereby mitigate the impending catastrophe of climate change?” Szapudi said (Sun ‘umbrella’, 2023).

Earth.com says that various designs are proposed for solar shields, and this involves deploying many tiny sunshade spacecraft to block the sunlight. Another one is placing massive orbital mirrors at the Lagrange Point to reflect the sun’s rays.

However, these SRM strategies can also divert the focus from reducing carbon emissions, which is the root cause of climate change. Additionally, solar shields are controversial because of their potential unforeseen or harmful climatic effects.