Solar ‘umbrella’ could help slow down global warming

István Szapudi, an astronomer at the University of Hawaiʻi Institute for Astronomy, has proposed building a solar “umbrella” that would shield the Earth from a fraction of the Sun’s light. 

This is not the first time that scientists have proposed a “solar shield” approach to preventing climate change. However, the majority of proposals to date have been rejected due to the large amount of weight needed to make a shield large enough to balance gravitational forces and prevent solar radiation pressure from blowing it away. 

Szapudi seems to have addressed this challenge by reducing the mass of the shield, while also using a captured asteroid as the counterweight. This would avoid the need to launch most of the device’s mass from Earth.

“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.

Szapudi began with the goal of reducing solar radiation by 1.7 per cent, an estimate of the amount needed to prevent a catastrophic rise in global temperatures.

During his research, he found that placing a tethered counterbalance towards the Sun could reduce the weight of the shield and counterweight to approximately 3.5 million tons – about one hundred times lighter than previous estimates for an untethered shield. 

Despite the design improvements, the shield would still weigh about 35,000 tons – and that would only account for 1 per cent of the device’s total mass. At the moment, the largest rockets developed can only lift about 50 tons to low Earth orbit, making the solar shield proposal unlikely to materialise in the near future. 

The proposal has been published in Proceedings of the National Academy of Sciences.