【雅虎】气候变化加剧了南加州火灾吗？ [美国媒体]

Did Climate Change Worsen the Southern California Fires?      

气候变化加剧了南加州火灾吗？      

The Atlantic•December 7, 2017
      
Massive wildfires are raging across Southern California, threatening thousands of homes and cultural landmarks like the Getty Museum in Los Angeles. Some of the largest fires were still barely contained by Wednesday afternoon.
      
大规模的野火在南加州肆虐，威胁着数千房屋和文化地标，如洛杉矶的盖蒂博物馆。到星期三下午，还没能控制住那些规模最大的野火。
      
It’s been an unusually bad year for the state—amid an unusually bad year for the West at large. Fires in California have destroyed more than 6,000 structures and incinerated hundreds of thousands of acres. Montana and British Columbia both also had some of their worst wildfire seasons ever.
      
广大的西海岸包括加利福尼亚都经历了异常糟糕一年。加利福尼亚的大火摧毁了6000多栋建筑，烧毁了数十万英亩的土地。蒙大拿和不列颠哥伦比亚省也经历了它们最糟糕的野火季节。
      
Of course, most years are bad wildfire years now. Seven of California’s 10 largest modern wildfires have occurred in the last 14 years. (The state began keeping reliable records in 1932.) Given the scale of the blazes, and their increasing regularity, it makes sense to ask: Does global warming have anything to do with this?
      
当然，现在大多数年份都有严重的野火。加利福尼亚州10场最大的现代野火中有7场发生在最近14年内。（自1932年加州开始有可信记录以来。）鉴于大火的规模和频率的增加，有必要问：全球变暖与此有关吗？
      
The answer isn’t as clear-cut as it was this summer, when drought- and heat-stoked fires raged across the Rockies and Pacific Northwest. Instead, a mix of forces are driving the fires in Southern California, and only some of them have a clear connection to global warming.
      
答案并不像今年夏天那样明显，当时干旱和高温引发的火灾落基山脉和西北太平洋地区在蔓延。不同的是，正助长南加州火灾的多种力量中，只有一些与全球变暖有明确的联系。
      
“These fires are not immediately emblematic of climate change,” said John Abatzoglou, an associate professor of geography and climate at the University of Idaho, in an email. “Yes, California did have the warmest summer on record. But the big anomaly here is the delay in the onset of precipitation for the southland that has kept the vegetation dry and fire-prone.”
      
爱达荷大学地理与气候学副教授John Abatzoglou在一封电邮中表示：“这些大火并不是气候变化的直接象征。是的，加州经历了有记录以来最热的夏天。但大的异常是南方降水推迟，使植被干燥易燃。”
      
In other words, late-fall and winter rains would normally end California’s fire season in November. Because those rains haven’t yet arrived, the blazes continue.
      
换言之，深秋和冬季的降雨通常会在11月结束加州的火灾季。因为降雨还没到来，所以大火还在继续。
      
“At least in Southern California right now, we are largely seeing textbook wildfires,” said Alexandra Syphard, a senior research scientist at the Conservation Biology Institute who studies fires. “Wind-driven fire events occur most typically in the fall, but can also occur like this, later in the year with fast-spreading, ember-driven fires under Santa Ana wind conditions.”
      
“至少现在在南加州，我们主要看到的是教科书似的野火”，研究火灾的保护生物学研究所的高级研究员Alexandra Syphard说。“风力助长火灾事件通常发生在秋季，但也可以像今年这样出现的更晚，在圣安娜风条件下发生火星迅速蔓延，到处引燃的火灾。”
      
Here are some of the biggest factors that are shaping the wildfires in California—and how global warming is or isn’t changing them:
      
下面是造成加州野火的一些最重要的因素，以及全球变暖是如何改变（也许没有改变）它们：
      
The Santa Ana winds
      
圣安娜风
      
Blame for the wildfires in Ventura and Los Angeles counties lies first and foremost with the Santa Ana winds, famously hot and desiccating gusts that blow from the desert to the coast. The Santa Anas also set the stage for the massive wildfires in Napa and Sonoma earlier this year.
      
圣安娜风（以热且干燥闻名，从沙漠吹向海岸的阵风）是发生在文图拉和洛杉矶县的野火的罪魁。圣安娜风也为今年早些时候纳帕和索诺玛的大规模野火提供了舞台。
      
Fires depend on two variables—an ignition source and fuel to burn—and the Santa Ana winds increase the availability of both. First, they dry out vegetation, creating more fuel across the landscape. Second, they blow trees and other debris against power lines, providing the source of a spark.
      
火灾依赖两个变量—火源和可燃物—圣安娜风同时提高了这两者的可能性。首先，使植被干燥，在地面上制造了更多的可燃物。其次，将树和其他碎片吹向电线，造成了火花。
      
When the Santa Anas blow this late in the year, they can start fires. In fact, writes Abatzoglou, “all December fires in the southland since 1948 have been associated with Santa Ana wind.”
      
当圣安娜风吹得晚时，就能引发火灾。事实上，Abatzoglou写道，“自1948年以来，南加州所有12月的大火都与圣安娜风有关。”
      
But there are few signs—at least so far—that the Santa Ana winds are becoming more prent or that they’re systematically moving later in the year. The peak of Santa Ana season usually comes in September or October. There is no trend toward more or fewer Santa Ana fires—or Santa Ana winds generally—in the historical record, Abatzoglou told me.
      
但是至少到目前为止，几乎没有迹象表明，圣安娜风正在变得更加盛行，或者今年系统性移动地较晚。圣安娜季节的高峰通常是在9月或10月到来。Abatzoglou告诉我，在历史记录中圣安娜大火（一般称圣安娜风）没有增多或减少的趋势。
      
A 2006 study from researchers at the University of California, Berkeley, and the Lawrence Berkeley National Laboratory suggested that by the end of the century, Santa Ana winds may become more common. They may also form later in the year, including in December.
      
加州大学伯克利分校和劳伦斯伯克利国家实验室的研究人员在2006年的一项研究表明，到本世纪末圣安娜风可能会更加普遍。它们也可能形成时间更晚，包括12月。
      
La Niña
      
拉尼娜现象
      
There’s currently a weak La Niña in the tropical Pacific, which means that global temperatures are cooler than they would be otherwise.
      
目前太平洋热带地区出现了弱拉尼娜现象，这意味着全球气温比以往要凉爽。
      
The same phenomenon is also keeping storms from making landfall in Southern California. Normally, California’s wet season would have started by this time of year. “Once [autumn] rains hit the region, fuel moistures recover and make the landscape fire-resistant, thus reducing the odds that a power-line failure or vehicle will start a fire,” said Abatzoglou.
      
同样的现象也阻止了风暴在南加州登陆。通常加利福尼亚的雨季在每年的这个时候已开始。Abatzoglou说：“一旦该地区（秋季）降雨到来，燃烧物恢复湿润，并使景观不易燃，从而减少电力线路故障或车辆引起火灾的可能性。
      
But the rains haven’t yet appeared, he told me. “So far this autumn, much of the southern half of California is pitching a shutout in terms of rainfall to date. Some of this is characteristic of La Niña ... as the southern tier of the United States sees less precipitation during La Niña winters.”
      
但降雨还没有出现，他告诉我：“今年秋季到目前为止，南加州的大部分地区降雨都迟到了。部分符合是拉尼娜现象的特征，因为美国的南部地区在拉尼娜现象下的冬季降水较少。”


      
It’s still unclear how climate change will affect the Pacific’s yearly dance between El Niño, La Niña, and a neutral state. A 2015 study in Nature Climate Change found that the Pacific Ocean may careen between extreme states—from an intense El Niño to a monster La Niña—by the end of the century, but more research on the question still needs to be done.
      
目前还不清楚气候变化将如何影响太平洋每年一度的厄尔尼诺现象、拉尼娜现象和中间状态之间的舞蹈。2015的一项自然气候变化研究发现，到本世纪末，太平洋可能倾向在极端状态之间变换—从强烈的厄尔尼诺现象到怪物般的拉尼娜现象—但这个问题还需要更多的研究。
      
A very cold U.S. East Coast
      
非常寒冷的美国东海岸
      
Even as the West Coast remains warm and dry, the Eastern Seaboard is settling into some of its first cold weather of the season. This pattern—a warm West, a frigid East—is known as the North American winter dipole.
      
当西海岸保持温暖和干燥，东海岸正进入这个季节的第一个寒冷天气。这种模式—西部温暖，东部寒冷—被称为北美冬季两极。
      
It’s caused when the jet stream—which both ferries storms into the continent and generally divides warm air from cold air—gets especially twisted across North America. It rises far into the Canadian Northwest, keeping most of the western United States warm and dry; then it cascades down across the middle of the country, bringing cold air well into the U.S. Southeast.
      
这是因为当气流-两个风暴进入大陆，并通常从寒冷空气中分离出温暖空气-特别是扭曲着跨越北美。它生成后深入加拿大西北部，保持大部分美国西部温暖和干燥；然后它倾泻穿过中部，把冷空气带到美国东南部。
      
This phenomenon prolonged California’s drought during the first part of this decade, keeping any kind of storm system offshore. It also brought the infamous “polar vortex” down into the continental United States.
      
这一现象延长了加利福尼亚在这个十年中头几年的干旱，使任何类型的风暴系统都远离海岸。它还把臭名昭着的“极地漩涡”带到了美国大陆。
      
There are a number of theories about how this pattern comes to form, and most of them revolve around climate change, as Jason Samenow writes at The Washington Post.
      
有很多种理论研究这种模式如何形成，其中大多数都围绕着气候变化，Jason Samenow在华盛顿邮报上写道。
      
Daniel Swain, a climate scientist at the University of California, Los Angeles, argues that the ridge forms in part because the West is warming up much faster than the East. If this is the case, then scientists might expect to see the phenomenon fade in decades to come, as the East Coast catches up to the West.
      
加州大学洛杉矶分校的气候科学家Daniel Swain认为，山脊的形成某种程度上是因为西部比东北热得快。如果是这样的话，科学家将会期待这种现象在未来几十年中消失，因为东海岸正在赶上西海岸。
      
But a paper published this week in Nature Communications takes another view. It finds that the disappearance of sea ice over the Arctic Ocean could change the circulation of the Pacific Ocean, encouraging the jet stream to veer north. In other words, climate change will make something like the North American winter dipole keep reappearing.
      
但本周一篇发表在《自然通讯》上的论文又提出另一种观点。它发现北冰洋海冰的消失可能会改变太平洋环流，促使气流向北移动。换言之，气候变化将使类似北美冬季两极的现象不断重现。