为什么说“大气环流紊乱”是极端天气的元凶？

2023年的夏天总算过去了。

与很多人感受的一样，这个夏季全国平均气温仅次于1961年，是有纪录以来的历史第二高，而且北京等地单日气温测出了历史新高，40摄氏度以上已不鲜见；与很多人感受的不同，这个夏季平均降雨量并不大，但雨水在时间与空间上都高度集中，引发了洪涝与干旱并存的场景。再加上台风、雷暴、风雹、龙卷风等灾害天气的出现，“极端”可以说是2023年夏天的第一关键词。

To pick a key word for summer 2023, “extreme” must be a top candidate. We’ve had an average temperature of 22℃, the highest in recorded history except other than 1961. The rainfall has been limited but also concentrated, so much so that Beijing saw its heaviest rainfall since 2012 while some regions in the Northwest suffered from drought.

图源：央视网

从过去几个不幸很热的夏天中总结经验，我们似乎发现，每个极热的夏天背后都跟着一个极冷的冬天。那么2023年的冬天会很冷吗？

Unfortunately, experience from the past several years show that after every extremely hot summer there follows an extremely cold winter. So what about the winter in 2023? Will it be extremely cold?

与所有专家一样，中国气象局公共气象服务中心原气象服务首席专家朱定真教授并不愿意给这个问题一个“是”或者“否”的确定答案，毕竟2023年的冬天尚未到来。但可以确定的是，夏天极热、暴雨极强、冬天极冷其实是反映的是一回事，都是气候趋于极端化的表现。

For Zhu Dingzhen, retired chief expert for meteorological services at China Meteorological Administration Public Meteorological Service Center, it’s hard to answer with a definite “yes”, but the probability is very high. “There is no direct link between the temperatures of summer and winter,” he said, “but when the former is extremely high that’s a sign of the total climate system being turbulent, which means the latter has a much higher possibility of being extremely low.”

“极端的冷也好、热也好、旱涝也好，都是大气环流紊乱造成的，”朱定真表示，“夏天能热出新高度说明我们的气候的极端化程度加重了，这种背景下如果冬天冷出新纪录也并不奇怪。”

图源：微博@气象北京

就好比单摆，如果摆锤在一端摆幅已经很大，那在另一端也可能会很大，因为整个单摆的阈值已经提高了。但在摆锤没有摆到另一边之前，谁也没法给出肯定的答案。

The climate radicalization is like a swinging pendulum — the left side is swinging at a higher amplitude, so it’s possible the right side might swing higher too, although no one can be 100 percent sure.

值得注意的是，冬天冷出新纪录指的并不是平均气温低，而是指波动的单日气温可能很低。2021年北京冬天单日气温最低值打破历史纪录，但从整个冬天的平均温度来看依然是暖冬。地球整体在升温，每日气温的波动幅度、范围、频率都在变得更大。朱定真教授特别提醒：“暖冬是个气候概念，不等于冬季每天都很暖和，全球气候极端化的背景下，暖冬里也很容易出现极端寒潮天气事件，该做的防寒工作一定要做！”

Zhu stressed that extreme cold is more about weather than climate, referring to single-day temperatures rather the average temperatures of the whole season. A good example is the “warm winter” in Beijing 2021, which saw the lowest single-day temperature in history. “Warm winter doesn’t mean being warm every day,” Zhu warned: “especially with climate change intensifying, there might be quite frequent cold waves in warm winters, so one must always take caution.”

对“大气环流紊乱”这个说法，中国科学院大气物理研究所副研究员陈卫博士给出了进一步的解释。她拿出地球仪，演示了这一过程：

地球是赤道热两极冷，气流自然会从热带亚热带的高压地区往极地低压地区流动。受地转偏向力的作用，这一气流在北半球中纬度向右偏转为西风。正常情况下，极地的“冷”与赤道的“暖”之间存在明显的南北温度梯度，这使得西风带很强盛，存在于其中的环流也很稳定，起到阻挡北极冷空气南下的重任。

Chen Wei, an associate researcher at Institute of Atmospheric Physics, Chinese Academy of Sciences, explained that further in terms of the global atmosphere movement. As the air pressure near the ground is higher in hot tropical regions than in cold poles, there is always a constant air flow from the former to the latter that turns right in the northern hemisphere and becomes western wind in the middle latitude. “Such western wind is a protection wall that turns any cold wave from the north into western wind, thus preventing it from going further south,” Chen said.

但随着全球变暖加剧，北极增暖更为明显，与赤道间的温度梯度减弱，导致西风带减弱，极地涡旋变得不稳定，极涡内的冷空气分裂南下，寒潮就能大举南侵。所以，虽然全球温度在升高，我们冬天感受到的寒潮反而更强。全球变暖与极冷天气不冲突，缘由在此。

However, with climate change, the temperature in the arctic region is growing so the temperature gap with the celestial equator shrinks. Chen pointed out that this weakens the western wind in middle latitude regions thus weakening its ability to prevent cold waves from going south, which, combined with the increasingly frequent unstable polar vortex that unleashes more cold waves, the frequency of cold weather naturally gets higher.

更可怕的还在后边。结满了冰的北极本来像面大镜子，能把照射来的绝大部分太阳光线反射回太空，但随着海冰融化镜子越来越弱，反照率越来越低，于是融化的更快，导致北极以两倍于其他地区的速度增暖，称之为“北极增暖放大”现象，这一恶性循环一旦开启情况只会越来越坏。很多人都看过一张著名的照片，融化的浮冰上趴着一只瘦骨嶙峋的北极熊，在全球变暖趋势被逆转之前，这一情况只会越来越明显。

In worse conditions the process can turn into a vicious circle. The huge piles of ice in the Arctic are like a big mirror that reflects part of the solar rays back into space, but as they melt the reflection gets weaker so more heat is accumulated, accelerating the meltdown process, which in turn further weakens the reflection. Chen said that this is called the “Arctic amplifying effect”, a process which has already begun and won’t be reversed until humankind pulls the brake on global warming activities.

波动多了出问题的可能性自然就越高。9月初中国气象台发布的官方报告中，清楚地给2023年的夏天做了总结：

“暴雨过程频繁，华北、东北等地强降水引发严重洪涝灾害，出现明显‘旱涝急转’；台风生成和登陆个数少，但破坏力强，“杜苏芮”导致严重洪涝灾害；高温日数多，极端性强；短时强降雨、雷暴、风雹、龙卷等灾害多点散发，致灾性强。”

“Heavy rainfalls are getting more frequent and have caused severe flooding in North and Northeast China, causing U-turns between droughts and floods. Typhoons are few in number but more destructive in force, of which Typhoon Doksuri had caused heavy flooding. There are more days with high temperatures, of which some are highly extreme. More catastrophes such as short-term strong rainfall, lightening storm and hurricane are located more widely.”

京津冀特大暴雨霸屏热搜榜时，西北内陆正遭受旱灾，说这个夏天多灾多难一点都不夸张。中国人民大学生态文明研究院副院长王克教授指出，这种灾难是全方面的，甚至可以说是左右为难。

图源：中国气象局

“过冷和过热都会导致一些慢性病发病率上升；极端天气下很多工程不得不停工，即使不停工效率也会低很多；粮食作物会因为极寒或者极冷而减产，从而危害粮食安全；暴雨与内涝会在城市造成巨大的伤亡与财产损失，为防范这些损失又需要花巨资升级城市基础设施，这些都是成本。”

While for urban residents, a “weather catastrophe” might mean inconveniences of travelling or having to stay at home, for agricultural production that may mean actual losses. Some outdoor construction or engineering projects have to suspend or face lower efficiency in cold or hot weather;Crops might wither in extreme cold or die in heat, thus posing a bigger challenge to the national food security;The cities have to either face losses of floods or raise the standards of buildings to withstand such floods, both of which cost money.

对于城市居民来说，气候灾难可能意味着忽冷忽热的气温、意味着街道上的积水、意味着下大雨无法出门而迟到被扣钱。但对农业生产来说，气候灾难给人的感受可能更深。西瓜、早稻等夏天成熟的作物都需要在早春育苗，一场寒潮来袭，人在室内能够躲过去，但可能地里就不再有存活的秧苗。早在2006年4月，湖南宁乡县就遭遇了气温剧降伴随大风的强寒潮，当地早稻秧苗普遍青枯、发黄，甚至死苗，而过去17年里气候极端化程度可不止加剧了一点半点，寒潮袭击的新闻频繁许多。

很多人在网上看到过“全球变暖的十大好处”之类的帖文，这些帖文图文并茂、绘声绘色地讲述着西北内陆如何变得湿润，一些热带亚热带水果种植线如何北移，曾经的沙漠如何变成绿洲。陈卫博士表示，毕竟大气升温后能容纳的水汽增多了，全球降水不确定性增大，曾经干旱的地区迎来更多强降雨并非不可能。

There have been doubts and challenges that climate change is a lie. There were even some articles that went viral carrying headlines such as “10 benefits of global warming”, which claim that with the global warming process, some tropical or sub-tropical fruits would be able to be planted in northern regions while northwestern dry regions would become wet.

但是干旱地区多出来的降雨会很有限，因为大气输送水汽能力有限，将水汽运送到内陆损耗是很大的，指望这种极端天气带来的降水让沙漠变绿洲不现实。反而是本来就湿润的沿海地区会迎来更极端的降雨，甚至会出现海岸线上升、整座城市被淹没的末日场景。跟这些损失比起来，沙漠多出来的那点毛毛雨真的不算什么……

那怎么解释塔克拉玛干沙漠发洪水呢？2021年7月的视频在网上已经流传两年之久，洪水在沙漠里蔓延、骆驼游泳逃生是实实在在的。

朱定真教授揭开了“沙漠发洪水”现象背后的真相：降水只占一部分，导致洪水的还有高原冰盖加速融化的雪水！这可不是好事，雪山冰川是人类淡水的主要储备，也是人类多条大江大河的发源地。这么加速融下去，人类的水塔就干涸了。

2022年，也就是塔克拉玛干沙漠发洪水的第二年，世界水源地峰会发起人杨勇考察了长江源等几条国内主要河流的源头。他发现，在原本应该是丰水期的七八月，这里却有大片沙滩裸露着。长江、雅鲁藏布江、印度河、恒河都会受到影响。

甚至早在五年前，位于乌鲁木齐的中国科学院天山冰川观测试验站就观测到一组令人忧心的数据。在2016年4月到2017年4月间，1号冰川的东西两支分别退缩6.3米和7.2米，其中西支退缩速率为1993 年1号冰川分裂以来的最大值。

As early as April 2017, the Tianshan Mountain Glacier Observatory found that two branches of the No.1 glacier in that area had retreated by 6.3 and 7.2 meters respectively, of which the western branch saw its biggest retreat since its formation in 1993.

夏天极热、冬天极冷，旱的旱死、涝的涝死，海冰消融，大河枯水，这些问题有些初现端倪、有些则已经十分严重，而这一切的原因只是在过去几百年碳排放的积累效应下，因为地球平均气温上升了一度半度。

2022年9月，牛津大学在一份报告中指出，截止2050年全球气候变化可能将造成高达23万亿美元的经济损失。要知道，中国2022年GDP才不过18万亿美元。

In September 2022, a study by Oxford University researchers published on Joule, an online research magazine on global challenges, estimated that if the current trend continues, global climate change might cause a loss of $23 trillion by 2050. As a comparison, China’s GDP in 2022 was only $18 trillion.

2009年的哥本哈根会议设定了目标，要在本世纪末将全球升温限定在2摄氏度以内，2015年巴黎会议再度确认了这一与人类生死存亡相关的目标，但没有达成任何有约束力的协议。直到今天，中国“双碳”目标提出已久，各发达国家还在为谁分配多少碳排放额、谁提供多少补贴推诿扯皮。

It’s hard to imagine what would happen if the global temperature rises by 2 degrees, which is the dead limit set by Copenhagen Climate Change Conference in 2009 and stressed again by the Paris Conference in 2015. Unfortunately, even that goal will be hard to achieve because some key clauses of the Paris Agreement, such as the one about nationally determined contributions, are voluntary instead of legally binding, which means the participants have the choice to implement it or not as they wish.

王克教授特别指出，“气候极端化的进程是非线性的，大自然不会给人类留下太多的时间去适应。”2023年夏天，仅在北京就有29.7天气温超过35摄氏度，比往年平均数直接多出21.1天，且有5天超过40摄氏度，是非常危险的信号。

留给人类的时间不多了。

总监制: 邢志刚

策划：吴艳鹏

联合策划：杨勇 王明慧

统筹：王珊珊 富文佳 李畅翔

撰稿：张周项

视频：杨晓恒

实习生：陈雨舒 Eileen Jie

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