關於地球工程的陰謀論甚囂塵上，但它能幫助拯救地球嗎？

As the world grapples with the pressing issue of climate change, scientists are exploring various methods to cool the planet, one of which is geo-engineering. This term refers to the deliberate manipulation of the Earth's climate system to counteract global warming. Researchers from around the globe, including those in the UK, are investigating geo-engineering techniques to see if they can effectively reduce rising temperatures. However, there are significant concerns regarding the potential risks associated with these methods. Experts warn that geo-engineering could disrupt global weather patterns or even lead to unintended warming in certain regions. As interest in geo-engineering grows, so do the conspiracy theories surrounding it. Since January, BBC Weather has noted a surge in social media discussions about geo-engineering, with many users accusing the organization of concealing secret projects and attributing recent cool and wet weather to these techniques. In fact, mentions of geo-engineering on social media platforms have doubled this year compared to the last six months of 2023. nnOne of the most discussed geo-engineering concepts is the idea of reflecting sunlight back into space to cool the Earth. The most advanced form of geo-engineering currently being researched is direct air carbon capture, which involves removing carbon dioxide from the atmosphere. Small-scale facilities in Europe, the United States, and Canada are already operational, collectively capturing around 10,000 tonnes of carbon dioxide annually. However, this amount is minuscule compared to the approximately 35 billion tonnes of carbon dioxide emitted globally each year. Professor Liz Bentley, the chief executive of the Royal Meteorological Society, emphasizes the need to explore alternative methods to limit further warming, suggesting that geo-engineering could be a valuable topic for discussion. nnDespite the potential benefits, some experts caution against viewing geo-engineering as a quick fix for climate change. They argue that it may divert attention from the more critical task of reducing carbon emissions. The concept of reflecting solar radiation may sound far-fetched, but it has natural precedents. For instance, during volcanic eruptions, vast amounts of ash and aerosols are released into the atmosphere, which can reflect sunlight back into space. The eruption of Mount Pinatubo in the Philippines in 1991 resulted in a global temperature drop of 0. 5 degrees Celsius over the following years. This raises the question: could we replicate such volcanic effects to cool the planet? Professor Jim Haywood, an atmospheric scientist at the University of Exeter, urges caution, stating that while it is essential to understand the negative impacts of climate change, it is equally important to consider the potential side effects of any geo-engineering interventions. nnResearchers are currently investigating two primary methods of solar radiation management: marine cloud brightening and stratospheric aerosol injection. Marine cloud brightening involves spraying fine saltwater from boats into low-level clouds over the ocean to enhance their brightness and reflectivity. Studies suggest that if a large area of the ocean, approximately 4% near the equator, were treated in this manner, it could have significant global impacts. The atmosphere is a complex system with no borders, and changes in one area can affect weather patterns worldwide. For example, brightening clouds off the coast of Namibia could lead to drought conditions in South America, particularly in Brazil, where the rainforests are located. Drought in the Amazon rainforest, often referred to as the lungs of the planet due to their carbon dioxide absorption capabilities, could have devastating consequences. nnWhile marine cloud brightening is being explored for its potential to mitigate global temperature rise, some researchers are also looking at its application on a smaller scale. Following a mass coral bleaching event in the Great Barrier Reef in 2016, scientists at Southern Cross University in Australia have been conducting trials to use cloud brightening techniques to protect coral-rich areas from marine heatwaves. The technology to perform marine cloud brightening on a small scale already exists, but stratospheric aerosol injection requires further advancements. This method involves artificially introducing aerosols, such as sulphate, into the stratosphere, which extends from 6 to 12 miles above the Earth. These aerosols would reflect some solar radiation, theoretically leading to global cooling. However, the logistics of injecting sufficient aerosols into the stratosphere remain uncertain. For instance, the cooling effect observed after the Mount Pinatubo eruption was due to the release of approximately 15 million tonnes of sulphur dioxide. nnThe potential risks associated with stratospheric aerosol injection are significant. A recent study indicated that this method could cause warming in the upper atmosphere, leading to changes in large-scale weather patterns. This could result in adverse effects in various regions of the world. In 2022, a group of scientists signed an open letter advocating for a global non-use agreement on solar radiation management, expressing concerns about the poorly understood dangers of these techniques. They worry that even theoretical research could lead to real-world experiments without fully comprehending the potential downsides. Conversely, some scientists argue that the risks of not exploring solar radiation management are greater than the risks of investigating it further. They contend that misinformation and conspiracy theories are hindering research efforts. Dr. Ramit Debnath, an assistant professor at the University of Cambridge, notes that many potential funders are hesitant to support research in this area due to fears of being targeted by conspiracy theorists. nnOne prevalent conspiracy theory is related to 'chemtrails,' which suggests that the white streaks left by planes in the sky are evidence of a secret plot to spray harmful chemicals. In reality, these streaks are simply contrails, which are formed from condensed water vapor emitted by jet engines. Contrails can actually contribute to warming the planet, and they are unrelated to the geo-engineering techniques currently under investigation. Dr. Debnath explains that discussing solar radiation management on social media often leads to accusations of attempting to harm people. The UK government has not yet deployed any geo-engineering techniques and has no plans to do so. However, they are investing in research to better understand the risks involved. The Natural Environment Research Council is currently seeking applications for a £10. 5 million fund to conduct 'risk-risk analyses' to determine whether the negative impacts of geo-engineering are greater than the damage caused by climate change. Professor Bentley emphasizes that geo-engineering is not a silver bullet that will solve all problems, but it could be part of a broader range of solutions to address climate change.