Solar geoengineering, if misused, could trigger catastrophic climate consequences, scientists caution. A recent report highlights the potential for solar geoengineering to intensify North Atlantic hurricanes, decimate the Amazon rainforest, and induce droughts in African regions if employed by unauthorized entities in specific regions of the planet. However, if the technology to block sunlight is utilized globally and harmoniously over an extended period, spanning decades or even centuries, there is substantial evidence suggesting it could effectively reduce global temperatures. The UK's Royal Society report underscores the necessity for a critical evaluation between the risks of geoengineering and those associated with ongoing global warming, which is already claiming lives and livelihoods. The logistics of large-scale geoengineering efforts are daunting, yet the costs are relatively modest compared to climate action, estimated at billions of dollars annually, in contrast to trillions. The report emphasizes that geoengineering merely addresses the symptoms of the climate crisis, failing to address the root cause: the burning of fossil fuels. It should complement, not replace, emission reductions. 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 impacting vulnerable people and ecosystems. Prof Keith Shine from the University of Reading underscores the importance of a scientifically informed, globally coordinated, and internationally agreed-upon strategy for deployment, emphasizing the need to balance the risks of climate change with the potential risks of geoengineering. The scientific community is divided on geoengineering research. Some advocate for continued research to enhance understanding of its effects, while others argue that further research increases the likelihood of its use, as it may be perceived as a rapid solution to the climate crisis. The Royal Society report, while non-committal, aims to provide a comprehensive overview of current knowledge to inform ongoing debates. The report focuses on two feasible and effective geoengineering methods. The first involves using high-altitude aircraft to inject 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, which released 15 million tons of SO2, offer natural examples of this process, demonstrating its potential to lower global temperatures. For significant geoengineering programs, approximately 8-16 million tons of SO2 per year are required. The second method, marine cloud brightening, involves releasing salt particles from seawater into the lower atmosphere, enabling water vapor to form clouds that reflect sunlight. This phenomenon is already observed in the clouds created by shipping pollution. 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 northern hemisphere deployment could lead to droughts in the Sahel region of North Africa. Tropical deployment could cause Mediterranean droughts. Marine cloud brightening in the southeast Atlantic could result in Amazon dieback, releasing vast carbon amounts, while eastern Pacific deployment could trigger a significant La Niña event with global implications. Prof Jim Haywood from the University of Exeter stresses the importance of avoiding unilateral action by rogue actors, as they may inadvertently cause regional temperature reductions. Some commercial companies have raised millions of dollars to pursue private geoengineering efforts, raising concerns about the potential for commercialization without adhering to objective, critical, and transparent standards. Even with international agreement and coordination, uncertainties persist regarding the extent of Earth cooling and regional impacts. In April, the UK's Advanced Research and Invention Agency launched a £50 million government-funded geoengineering program, including small-scale outdoor experiments. Prof Mark Symes, leading the Aria program, cites the threat of climate tipping points as a compelling reason for solar geoengineering research. However, past outdoor experiments have faced cancellation due to strong opposition, highlighting the need for careful consideration and public engagement in this controversial field.
