PBS高端访谈:日光与水的奇幻戏法（在线收听）

Hari Sreenivasan: Once a year, California's Yosemite National Park plays host to an impressive trick of sunlight and water on the vertical rock formation known as El Capitan. But warmer weather this year led to disappointment. Christopher Booker has more.

Christopher Booker: For a few weeks each February, a natural spectacle draws thousands of people to California's Yosemite National Park. It's called Firefall. It only lasts for a few minutes at sunset when the winter light hits the park's towering Horsetail Falls. At just the right angle. But this year, there was no firefight. Patrick Gonzalez is a professor with the University of California, Berkeley. He says this year there wasn't enough water. The reason, climate change.

Patrick Gonzalez: The more snow that you have in the winter, the more water that you'll have coming over the falls. Our analysis show that total annual rainfall and snowfall has decreased across all of Yosemite National Park.

Christopher Booker: And Gonzalez says Firefall is not the only part of the park that's being impacted by climate change.

Patrick Gonzalez: Our analysis of climate data shows that human caused climate change has heated the park 1.1 degrees Celsius or 2 degrees Fahrenheit. That might not sound like a lot, but 1.1 degrees Celsius is the equivalent of pushing a mountain down a hundred and eighty meters or six hundred feet, more than the height of the Washington Monument, from cooler areas at high elevation to warmer areas below. In Yosemite and across the western U.S., human-caused climate change has doubled the area of wildfire burned, has doubled tree death, and has shifted trees upslope into meadows.

Christopher Booker: In recent years due to concerns over the ecological damage that come with large crowds gathering in Yosemite. The National Park Service has tried to limit the number of people who come to watch Firefall. But as the climate continues to change, such restrictions may no longer be necessary.

哈里·斯里尼瓦桑：加州约塞米蒂国家公园每年都有那么一次会在竖向的岩石结构埃尔卡皮坦上表演日光与水交错的奇幻戏法，令人过目难忘。但今年由于天气变暖，所以只能让大家失望了。下面请听克里斯多夫·布克发回的报道。

克里斯多夫·布克：每年2月都有那么几周的时间，一处自然奇观都会吸引数千人来到加州约塞米蒂国家公园的火瀑布。日落时分，奇观只会持续数分钟的时间，发生的条件是冬日的阳光与公园的高耸的马尾瀑布以正确的角度交汇。但今年却没有奇观出现。帕特里克·冈萨雷斯是伯克利加州大学的教授。帕特里克表示，今年的水不够充足。原因是气候变化。

帕特里克·冈萨雷斯：冬天的雪越多，瀑布的水就越多。我们的分析显示，约塞米蒂国家公园每年的降雨量和降雪量都减少了。

克里斯多夫·布克：冈萨雷斯表示，火瀑布不是公园里唯一一处受气候变化影响的地方。

帕特里克·冈萨雷斯：我们对气候数据的分析显示，人类引发的气候变化已经导致该公园温度上升1.1摄氏度（2华氏度）。这个数字听起来可能不多，但1.1摄氏度等同于让一座山下降180米，也就是600英尺——超过了华盛顿纪念碑的高度——从高海拔的寒冷地区到低海拔的暖和地区。在约塞米蒂国家公园和美国西部，人类引发的气候变化已经导致野火波及的地区扩大一倍，导致树木死亡数量翻番，导致树木上坡变成了草地。

克里斯多夫·布克：近年来，由于人们担心生态系统因大批人来到该公园而遭到破坏，国家公园管理局试着限制访问火瀑布的游客人数。但气候一直在变化，这样的限制措施可能不再必要。