PBS高端访谈:高温加速冰盖融化速度（在线收听）

Hari Sreenivasan: Europe broke heat records this past week. Paris recorded an all time high temperature of 108.7 degrees. That heat is now moving north toward the Arctic. Over the next few days and so-called heat dome is expected to form, raising concerns among climate scientists. They're worried about ice melt, rising sea levels and more. Washington Post reporter Andrew Freedman covers weather and climate and he joins us now from Washington DC. First a little science explainer. What's a heat dome?

Andrew Freedman: Yeah so a heat dome is basically a high pressure area, kind of in the mid to upper levels of the atmosphere that forms this kind of bubble, if you will, where the air within it is sinking and heating and weather systems around it are basically rerouted as if there was a detour in the atmosphere.

Hari Sreenivasan: Okay. So as this heat dome moves over the Arctic, we're expecting higher temperatures than normal. And then what happens?

Andrew Freedman: So we're expecting potentially exceptional melt event this week over the Greenland ice sheet that could potentially lead us to new record losses in sea ice and new record melt in Greenland and Greenland ice melt raises sea levels.

Hari Sreenivasan: Is there a cycle that this feeds into as the ice melts and the sea level rise? What happens?

Andrew Freedman: It's sort of like ice cubes floating in a glass of water. It doesn't raise sea levels but what it does is it exposes more dark ocean water to incoming sunlight which raises the ocean temperatures which in turn melts more sea ice. So there is a positive feedback there.

Hari Sreenivasan: What are scientists going to do about this? How are they planning to study this, the ripple effects of what could happen in the next week and a half, two weeks?

Andrew Freedman: Scientists are up there. They're up there on boats, they're up there on the ice sheet. But when talking to these scientists you know the sense of a system that is getting into sort of a runaway feedback really comes through. So you can tell that there is the potential for these types of events to encourage very severe impacts in to future decades and into future years.

Hari Sreenivasan: In the past couple of weeks we also saw stories about forest fires in the Arctic Circle. Does that also contribute to this feedback loop? What happens to the ash? Where that lands?

Andrew Freedman: So right now we've seen the warmest June on record, warmest July so far. It'll be the warmest July on record in Alaska. That state has seen over 2 million acres burn already this fire season. There are forest fires burning all across Siberia. This releases more carbon dioxide and other greenhouse gases which further warms the planet. And also where this ash is going, a lot of this is landing on the ice sheet. So on either Greenland or on sea ice. So when you get a darkening of the ice that obviously makes the ice less reflective which allows more heat to be absorbed which helps melt the ice.

Hari Sreenivasan: All right these are all big cycles that we're talking about. Washington Post reporter Andrew Freedman joining us from Washington D.C. Thanks so much.

Andrew Freedman: Thanks for having me.

哈里·斯里尼瓦桑：欧洲上周已经突破了高温纪录。巴黎达到史上最高的108.7度。热浪现在正朝着北极移动。未来几天里，所谓的热圆顶天气现象将会形成，这引发了气候科学家的担忧。他们担心冰川融化、海平面上升等问题出现。《华盛顿邮报》记者安德鲁·弗里德曼是天气与气候播报专员，今天，身在华盛顿的他也与我们取得了连线。首先，咱们稍微解释一点科学问题——什么是热圆顶呢？

安德鲁·弗里德曼：好的，所谓热圆顶，它是一片高压区域，它会出现在高层大气的中部，形成这种气泡。气泡内部的空气会下沉，同时温度也在升高，这导致其附近的天气系统改变方向，就好像大气层绕道了一样。

哈里·斯里尼瓦桑：好的，所以这种热圆顶正在北极上空，所以我们预计会有比正常温度高的高温出现。那么我想问接下来会发生什么呢？

安德鲁·弗里德曼：本周，预计格陵兰冰川会出现大量融化。这会导致我们失去大量海洋冰层，达到前所未有的成都，而且格陵兰地区也会出现破纪录的冰层融化，导致海平面上升。

哈里·斯里尼瓦桑：冰层融化和海平面上升是否有什么周期可言呢？如果发生的话，会怎样呢？

安德鲁·弗里德曼：就会有点像冰块漂浮在水上的感觉。这倒不会导致海平面上升，但是会让更广阔的海洋深处暴露于即将出现强烈日照之下，从而导致海水温度升高。继而使得海洋冰层融化。所以这里是有积极反馈的。

哈里·斯里尼瓦桑：科学家要对此做出什么响应呢？他们计划如何研究这个呢？未来一周半乃至两周的时间里，会发生什么连锁反应吗？

安德鲁·弗里德曼：科学家已经在关注了，他们乘船去往那里了，观测了冰层的情况。但是跟这些科学家交谈的时候就会感受到有那么一个系统已经失控了。所以你可以知道这些事件的发生会导致非常严重的影响，甚至影响到未来几十年。

哈里·斯里尼瓦桑：在过去几周的时间里，我们还看到有报道称北极圈出现了森林失火。这件事是否也导致了这样的反馈循环呢？

安德鲁·弗里德曼：今年的6月是史上最热的6月。也是阿拉斯加史上最热的6月。阿拉斯加州在当前的火灾季已经有200多万公顷土地失火了。西部利亚全境都发生了山火事件。山火事件释放的二氧化碳等温室气体会进一步导致全球变暖。随着火势的蔓延，冰层也会受到影响，无论是格陵兰冰层还是海洋冰层。冰层颜色变深后，反射光的能力会下降，就会吸收更多的热量，就会有更多的冰层融化。

哈里·斯里尼瓦桑：这些都是我们在讨论的一些恶性循环。感谢《华盛顿邮报》记者安德鲁·弗里德曼从华盛顿发回的报道，谢谢你。

安德鲁·弗里德曼：感谢节目组与我连线。