With increasing global warming, people are desperately looking for solutions to the climate problem. Researchers are now proposing to dim some of the sunlight with a gigantic carpet of bubbles in space. In theory it sounds tempting – but many hurdles remain.
Climate change threatens to elude mankind. Heat waves are becoming more common. Researchers are already warning that the 1.5 degree warming threshold could fall in the coming years. This was once considered the target upper limit for permanent warming that the countries of the world had agreed to in the Paris Climate Agreement in 2015. At the same time, global mass emissions of CO2 continue. So what to do?
One solution could be solar geoengineering. The basic idea: a fraction of the sunlight is simply reflected away from the earth. Because the less sunlight reaches the earth’s atmosphere, the less it warms up.
For example, there is the idea of distributing aerosols in the stratosphere that reflect sunlight. This actually works – when the Pinatubo volcano in the Philippines erupted in 1991, it was observed that the earth cooled by around 0.3 to 0.5 degrees due to the sulfur dioxide blown into the high air layers. But there are numerous concerns about imitating something like this technically, for example with fleets of airplanes. Because it is difficult to get rid of aerosols if the whole thing does not have the desired or even negative effects on the climate.
Another approach is giant, space-based solar shields that dim the sunlight a bit. According to calculations, a 1.8 percent reduction in solar radiation could already reverse global warming. Researchers at the renowned Massachusetts Institute of Technology (MIT) in the USA are now presenting a new concept of this type. Her sunshield consists of a giant “raft” of frozen bubbles. It is said to be roughly the size of Brazil and to be positioned 2.5 million kilometers from Earth in front of the sun – near the so-called Lagrange point, where the gravitational forces of both celestial bodies cancel each other out.
The idea of building giant sunglasses for Earth is not new. There have been proposals in the past to launch large foils or a swarm of small spacecraft with sun shields. But the technical challenges are enormous. The biggest problem is getting the massive amounts of material into space. The MIT researchers’ solution: The bubbles should have wafer-thin shells in order to save material. According to calculations, they should be just 400 to 600 nanometers thin – a sheet of paper would be around 200 times thicker.
In the first experiments, it was already possible to inflate a thin-film bubble at a pressure of 0.0028 atmospheres and keep it at around minus 50 degrees – i.e. conditions that are roughly close to those in space, the researchers write in a statement. Possible materials are ionic liquids – salts that are already liquid at room temperature. ‘A key advantage of a bubble screen is the ability to be assembled in situ, using space-based manufacturing techniques,’ the authors said. Dismantling is also easy – the bubbles can simply be burst when they are no longer needed. “This would make solar geoengineering fully reversible and significantly reduce space debris.”
But the authors admit that a lot of research is still needed to make all of this a reality. For example, with a view to transporting the raw material or assembling the umbrella. Researchers are already thinking about futuristic space concepts, such as magnetic cannons (“railguns”) to shoot the necessary material into space – so far, however, such a thing has only existed on paper. In addition, the fragile structure would probably have to be constantly renewed. And the solar wind threatens to push it away over time, for which a solution would also have to be found.
There are other challenges: It is completely unclear, for example, how the reduced solar radiation will affect the earth’s weather. Scientists and environmentalists warned in an open letter earlier this year that the regional effects of solar geoengineering could be devastating. Thus, artificially weakening the sun’s radiative power would likely interrupt the monsoon rains in South Asia and West Africa. It could wipe out the rain-dependent agriculture there that feeds hundreds of millions of people.
In the end, the procedure may do more harm than good. And a supposedly simple technical solution to climate change could also reduce the urgency of reducing CO2 – in other words, humanity would possibly continue as before. However, the authors emphasize that a parasol should at best support efforts to reduce CO2.
In addition, the whole thing has so far only been a working hypothesis, according to the MIT statement. However, if all the technical hurdles are overcome, the bubble sun shield could be built before the end of the century, before the worst effects of climate change hit. According to older calculations, the costs would be around 0.5 percent of global GDP – over a period of 50 years.