科學家表示，氣候變遷使洛杉磯火災變得更加嚴重

A recent study has confirmed that climate change has significantly contributed to the worsening of wildfires in Los Angeles. According to the research conducted by World Weather Attribution, a respected organization known for its studies on extreme weather events, climate change has made the hot and dry weather conditions that lead to these devastating fires about 35% more likely. The study highlights that the wildfire season in Los Angeles is becoming longer, while the rainfall that typically helps extinguish these fires is decreasing. The scientists involved in the study emphasize that wildfires are complex events influenced by various factors, but they are confident that a warming climate is increasing the likelihood of severe fire incidents in the region. Dr. Clair Barnes, the lead author of the study from Imperial College London, stated, 'Climate change increased the risk of the devastating LA wildfires. Drought conditions are more frequently pushing into winter, increasing the chance a fire will break out during strong Santa Ana winds that can turn small ignitions into deadly infernos. ' The Santa Ana winds are powerful gusts that blow from the inland areas of California towards the coast, and they can rapidly escalate small fires into large, uncontrollable blazes. The study comes in the wake of a series of destructive fires that broke out in early January, resulting in the loss of around 30 lives and the destruction of over 10,000 homes. The researchers focused on the conditions that make wildfires more likely, utilizing climate models to analyze how the warming of the planet since the mid-19th century has influenced heatwaves, droughts, floods, and fires. The extensive burning of fossil fuels, such as coal, oil, and gas, since the industrial revolution has released billions of tons of greenhouse gases into the atmosphere, acting like a blanket that traps heat and raises global temperatures by approximately 1. 2 degrees Celsius. By employing climate models and statistical methods alongside real-world observations, the World Weather Attribution team has been able to quantify the impact of climate change on extreme weather events. In the case of the LA fires, they discovered that the hot and dry conditions that fueled the fires are now expected to occur once every 17 years, representing a 35% increase in likelihood compared to a scenario without climate change. Dr. Friederike Otto, the head of World Weather Attribution, remarked, 'We actually see that the models show very much the same results that the real-world observations have. So there, in this combined index, we are quite confident about the result. ' The researchers also examined other critical factors that contribute to wildfires, including the duration of the fire season. Their analysis of weather data revealed that the fire season has lengthened by approximately 23 days since the onset of global warming around 1850. This extension means that the dry conditions and the Santa Ana winds, which are essential for the spread of fires, are increasingly overlapping. Drought is another significant factor in this equation. The study found that dry conditions in the Los Angeles area from October to December are now about 2. 4 times more likely than they were before the widespread use of fossil fuels. The researchers are clear in their assertion that climate change has heightened the probability of the hot and dry conditions that lead to wildfires. However, they express caution regarding the connection between rising temperatures and the lengthening of the fire season or the decrease in rainfall, noting that the models did not indicate a strong correlation. Despite these uncertainties, the overall conclusion is that a warmer world has increased the chances of devastating wildfires occurring, and as fossil fuel consumption continues, these chances will only rise. Prof. Gabi Hegerl from the University of Edinburgh, who was not involved in the study, stated, 'Overall the paper finds that climate change has made the Los Angeles fires more likely despite some statistical uncertainty. This is a carefully researched result that should be taken seriously. ' The new research builds upon earlier studies conducted while the fires were still raging, which linked the wildfires to a phenomenon known as 'precipitation variability. ' This concept suggests that years with heavy rainfall are often followed by very dry years, which increases the risk of wildfires. This pattern was evident in Los Angeles, where two wet winters were succeeded by an extremely dry autumn and winter, allowing the growth of grass and shrubs that later became fuel for the fires ignited by the strong Santa Ana winds.