The battle against global warming just got a new, controversial weapon: reflecting sunlight into space. But experts warn of a potential 'rogue nations' risk. The Royal Society, Britain's leading scientific body, suggests that reducing the amount of sunlight reaching Earth could help limit the damage caused by climate change. However, they caution that this approach is not without its risks and potential drawbacks. The society's new report highlights two strategies: pumping reflective particles high in the atmosphere and spraying salt into clouds over the sea to make them whiter. These methods could effectively dim the sun's rays and 'buy time' for fossil fuel emissions cuts to take effect. But here's the catch: a rogue nation acting alone could cause extreme droughts and weather disturbances elsewhere. Professor Keith Shine, chair of the report's working group, acknowledges the risks but argues that there may come a time when world leaders agree that solar radiation modification (SRM) is the least worst option. The report emphasizes that global efforts to reduce greenhouse gas emissions are unlikely to prevent global temperatures from rising above the 1.5C 'safe' limit. In fact, under current policies, temperatures are projected to be at least 3C warmer than pre-industrial levels by 2100. The most promising option for dimming sunlight, according to the report, is stratospheric aerosol injection. This involves planes releasing sulphur dioxide gas at high altitudes, forming particles that reflect a small amount of sunlight. Interestingly, real-world evidence supports this idea. The 1991 eruption of Mount Pinatubo in the Philippines reduced temperatures by 0.5C for one to two years after pumping 15 million tonnes of sulphur dioxide into the stratosphere. Computer models suggest that releasing 8-16 million tonnes of the gas annually from planes in both hemispheres could lower global temperatures by 1C. While the cost of this strategy is estimated to be 'in the low 10s of billions of dollars a year,' it's a small price compared to the global cost of extreme weather, wildfires, and other climate impacts. For instance, Hurricane Melissa, intensified by global warming, caused up to $52 billion in damage and economic losses across the western Caribbean. However, the Royal Society's report also stresses that SRM is not a solution to the root cause of climate change and should not replace emissions reductions. Instead, it could be a temporary measure to reduce temperatures while carbon dioxide levels peak and begin to fall, potentially requiring deployment for 100 years or more.
