What once sounded like science fiction - cooling the Earth by reflecting sunlight - is now being seriously explored by leading scientists and institutions. The idea is called solar geoengineering, and it’s gaining traction as climate projections grow more alarming. One method, Stratospheric Aerosol Injection (SAI), would involve spraying particles into the upper atmosphere to reflect solar radiation and lower global temperatures. While it’s still controversial, research is accelerating because carbon emissions aren’t falling fast enough, and the effects of climate change are intensifying more quickly than expected.

The concept isn’t just theoretical. In 1991, Mount Pinatubo in the Philippines erupted, sending 20 million tons of sulfur dioxide into the stratosphere. The result? A temporary global cooling of about 0.5°C. SAI aims to mimic that natural effect by injecting sulfur dioxide at high altitudes. It could quickly lower sea temperatures, slow glacial melt, and reduce coral bleaching. But it’s not a climate solution - it doesn’t remove CO2 or reduce ocean acidification. And once started, it would likely need to continue for decades or even centuries. If stopped abruptly, temperatures could rebound quickly, giving ecosystems and societies little time to adapt.

There are serious concerns. Because most research has been done through computer modeling, no one can fully predict how large-scale deployment would affect weather, agriculture, or ecosystems. Some models show changes in rainfall patterns or a weakening of the ozone layer. In one case, cooling the Indian Ocean to help one region triggered drought in another. Even minor shifts - like where or how high the particles are released - can create different outcomes. And because there’s no global agreement to regulate this technology, there’s a risk that a single country or private actor could act unilaterally, impacting the entire planet.

Small experiments are already underway. One planned high-altitude balloon test in Sweden was cancelled after protests, but similar releases have been carried out by researchers in the UK. A private company has launched dozens of balloons claiming to offset warming, despite having no official approval. Another method being tested is marine cloud brightening, where sea salt is sprayed into the air to enhance cloud reflectivity. It’s being explored to protect coral reefs, but research shows it could also alter global weather patterns like El Niño and increase heat in certain regions.