Solar geoengineering, a potential solution to combat climate change, carries significant risks if it falls into the wrong hands, scientists warn. The technology, which involves blocking sunlight to cool the planet, could have unintended consequences if deployed unevenly across the globe. For instance, solar geoengineering might intensify North Atlantic hurricanes, decimate the Amazon rainforest, and cause droughts in parts of Africa if executed by rogue actors. However, if implemented globally and in a coordinated manner for an extended period, it could effectively lower global temperatures, according to a report from the UK's Royal Society. The report highlights a critical dilemma: the world is failing to address the climate crisis, and geoengineering might become a necessary consideration. As global heating continues to claim lives and livelihoods, scientists must weigh the risks of geoengineering against the dangers of inaction. The logistics of large-scale geoengineering are complex, but its cost is relatively small compared to the trillions spent on climate action. However, geoengineering only treats the symptoms of climate change, not the root cause: the burning of fossil fuels. Abruptly halting geoengineering without reducing emissions could lead to a termination shock, causing temperatures to rise rapidly by 1-2C within a few decades, severely affecting ecosystems and populations unable to adapt quickly. Prof Keith Shine from the University of Reading emphasizes the need for a scientifically informed, globally coordinated strategy if policymakers decide to deploy geoengineering. The scientific community is divided on the issue. Some researchers advocate for continued research to understand the potential effects, while others argue that further study increases the likelihood of its use, driven by the desire for a quick fix to the climate crisis. The Royal Society's report, which does not take a stance, aims to provide a comprehensive overview of the current understanding of geoengineering to inform public debate. The report focuses on two feasible and effective geoengineering methods. The first involves using high-altitude aircraft to pump sulfur dioxide (SO2) into the stratosphere, creating reflective particles that bounce sunlight back into space. Volcanic eruptions, such as Mount Pinatubo's eruption in 1992, have naturally demonstrated this process, lowering global temperatures by 0.5C for a couple of years. For significant geoengineering, approximately 8-16 million tons of SO2 per year would be required. The second method is marine cloud brightening, where salt particles from seawater are injected into the lower atmosphere, enabling water vapor to form clouds that reflect sunlight. This process is already observable in the clouds created by shipping pollution. However, the global climate is a complex interplay of ocean, land, and air systems. Research indicates that deploying stratospheric sulfur dioxide injection in the southern hemisphere could intensify North Atlantic hurricanes, while deployment in the northern hemisphere could lead to droughts in the Sahel region of north Africa. Deploying it only in the tropics could cause droughts in the Mediterranean. Marine cloud brightening in the southeast Atlantic could result in the dieback of the Amazon, releasing vast amounts of carbon, while deployment in the eastern Pacific could trigger a massive La Niña, with far-reaching global consequences. Prof Jim Haywood from the University of Exeter stresses the importance of global coordination to avoid unintended regional impacts. Despite the potential risks, some commercial companies have raised millions of dollars to pursue private geoengineering efforts. Prof Mark Symes, leading the Aria program, cites the looming threat of climate tipping points as a compelling reason to research solar geoengineering. However, the commercialization of geoengineering raises concerns, and previous outdoor experiments have faced strong opposition and cancellation. The report underscores the need for transparent, critical research to address the uncertainties surrounding geoengineering's effectiveness and regional impacts, even with international coordination.
