As suffering grows and ecosystems unravel, more people will ask: is there anything we can do to prevent these harms? The idea of reflecting a small fraction of incoming sunlight to reduce warming is not a new idea. Earth already reflects about 30% of incoming sunlight; raising that fraction slightly – say, to 31% – could strengthen the planet’s natural heat shield. In 1991, Mount Pinatubo erupted and sent about 15m tonnes of sulfur dioxide into the stratosphere, cooling the planet by about 0.5C. That eruption became a natural experiment, and inspired the idea of stratospheric aerosol injection (SAI).

Source: The Guardian January 06, 2026 15:27 UTC