A sunshade at 50 kilometers altitude?

Imagine a giant sunshade floating high above the Earth, blocking a small portion of sunlight. It may sound like science fiction, but scientists are seriously exploring whether this idea could help cool the planet temporarily. A recent study now suggests a surprising location for such a sunshade: the upper stratosphere, about 50 kilometers above the ground.

The concept is drawn from nature. Large volcanic eruptions, such as Mount Pinatubo in 1991, release sulfur particles into the upper atmosphere. These particles reflect sunlight back into space, which leads to temporary global cooling. Researchers hope to replicate this natural process in a controlled way to slow down global warming for a limited time.

Why so high?
Earlier studies mostly looked at lower altitudes, around 20 kilometers. But this comes with serious drawbacks. At that level, particles can disrupt rainfall patterns and damage the ozone layer. New calculations show that deploying particles at 50 kilometers could work much better. At this height, the particles spread more evenly, remain suspended longer, and cause less harm to the climate system. The cooling effect is also more pronounced.

However, there is one major obstacle. No aircraft can currently reach that height. Rockets would be required, which makes the project far more complex and expensive.

Buying Time, Not a Miracle Cure
It is important to note that this sunshade would not remove any CO₂ from the atmosphere. Once the particles fall out, global temperatures would rise again. This approach could only serve as a temporary measure, buying time to cut greenhouse gas emissions more aggressively. At the same time, it raises important questions. Who gets to decide when we begin altering the atmosphere? And who decides when to stop?

Until now, most experiments have remained small, mainly due to public resistance. But an increasing number of countries are investing in research. Not to launch such a system immediately, but to be prepared if the climate crisis becomes even more severe. The question remains: will humanity, willingly or not, end up redesigning the planet?