联合国科学报告：全球升温成定局，极端天气将大幅增加
A Hotter Future Is Certain, Climate Panel Warns. But How Hot Is Up to Us.
BRAD PLUMER, HENRY FOUNTAIN
2021年8月10日
Nations have delayed curbing their fossil-fuel emissions for so long that they can no longer stop global warming from intensifying over the next 30 years, though there is still a short window to prevent the most harrowing future, a major new United Nations scientific report has concluded.
联合国一份新的重要科学报告得出结论称，各国在控制化石燃料排放方面已拖延了太长时间，使世界无法阻止全球变暖在未来30年加剧，但仍有一个防止最可怕未来的短暂时机。
Humans have already heated the planet by roughly 1.1 degrees Celsius, or 2 degrees Fahrenheit, since the 19th century, largely by burning coal, oil and gas for energy. And the consequences can be felt across the globe: This summer alone, blistering heat waves have killed hundreds of people in the United States and Canada, floods have devastated Germany and China, and wildfires have raged out of control in Siberia, Turkey and Greece.
人类自19世纪以来已让地球的温度升高了约1.1摄氏度，原因主要是为获得能源燃烧煤炭、石油和天然气。变暖的后果已在全球各地都能感受到：仅今年夏天，严酷的热浪就导致了美国和加拿大数百人死亡，洪水已给德国和中国带来了毁灭性灾害，野火也已在西伯利亚、土耳其和希腊失控。
But that’s only the beginning, according to the report, issued on Monday by the Intergovernmental Panel on Climate Change, a body of scientists convened by the United Nations. Even if nations started sharply cutting emissions today, total global warming is likely to rise around 1.5 degrees Celsius within the next two decades, a hotter future that is now essentially locked in.
但根据联合国召集的科学家组成的政府间气候变化专门委员会(Intergovernmental Panel on Climate Change)周一发布的报告，这仅仅是开端。即使各国从今天开始大幅减少碳排放，全球变暖的总升温很可能在未来20年内达到1.5摄氏度左右，一个更炎热的未来现在基本上已不可避免。
At 1.5 degrees of warming, scientists have found, the dangers grow considerably. Nearly 1 billion people worldwide could swelter in more frequent life-threatening heat waves. Hundreds of millions more would struggle for water because of severe droughts. Some animal and plant species alive today will be gone. Coral reefs, which sustain fisheries for large swaths of the globe, will suffer more frequent mass die-offs.
科学家发现，升温1.5度所造成的危险大大增加。全球各地有近10亿人将痛苦忍受更频繁的、威胁生命的热浪。还有数亿人会因严重干旱而缺水。一些现存的动植物物种将会灭绝。支撑着全球大片海渔业的珊瑚礁将遭遇更频繁的大规模死亡。
“We can expect a significant jump in extreme weather over the next 20 or 30 years,” said Piers Forster, a climate scientist at the University of Leeds and one of hundreds of international experts who helped write the report. “Things are unfortunately likely to get worse than they are today.”
“我们可以预计，在未来二三十年里，极端天气将大幅增加，”利兹大学(University of Leeds)的气候科学家皮尔斯·福斯特(Piers Forster)说，他是协助撰写这份报告的数百名国际专家之一。“不幸的是，事情可能会变得比现在已有的情况更糟。”
Not all is lost, however, and humanity can still prevent the planet from getting even hotter. Doing so would require a coordinated effort among countries to stop adding carbon dioxide to the atmosphere by around 2050, which would entail a rapid shift away from fossil fuels starting immediately, as well as potentially removing vast amounts of carbon from the air. If that happened, global warming would likely halt and level off at around 1.5 degrees Celsius, the report concludes.
但我们还有一线希望，人类仍然可以阻止地球变得更热。要做到这点，就需要各国共同努力，让大气中的二氧化碳含量在2050年前后不再增长，这将需要马上开始从化石燃料迅速转换到其他能源，还可能需要从空气中移除大量的二氧化碳。报告总结说，如果能做到这点，全球变暖的升温可能会停止在1.5摄氏度左右。
But if nations fail in that effort, global average temperatures will keep rising — potentially passing 2 degrees, 3 degrees or even 4 degrees Celsius, compared with the preindustrial era. The report describes how every additional degree of warming brings far greater perils, such as ever more vicious floods and heat waves, worsening droughts and accelerating sea-level rise that could threaten the existence of some island nations. The hotter the planet gets, the greater the risks of crossing dangerous “tipping points,” like the irreversible collapse of the immense ice sheets in Greenland and West Antarctica.
但是，如果各国在这方面的努力失败，全球平均气温将继续上升——与前工业化时代相比，升温可能超过2摄氏度、3摄氏度，甚至4摄氏度。报告描述了气温每升高1度会带来的更大危险，比如越来越凶猛的洪水和热浪，越来越严重的干旱，以及可能让一些岛屿国家的生存受到威胁的海平面加速上升。地球的温度越高，越过危险“临界点”的风险就越大，比如引发格陵兰岛和南极洲西部巨大冰盖不可逆的崩塌。
“There’s no going back from some changes in the climate system,” said Ko Barrett, a vice-chair of the panel and a senior adviser for climate at the National Oceanic and Atmospheric Administration. But, she added, immediate and sustained emissions cuts “could really make a difference in the climate future we have ahead of us.”
“气候系统的一些变化已经无法逆转，”该委员会副主席、美国国家海洋和大气管理局(National Oceanic and Atmospheric Administration)气候问题高级顾问柯·巴雷特(Ko Barrett)说。但是，她补充说，立即和持续的减排“有可能对我们面临的气候未来产生影响”。
The report, approved by 195 governments and based on more than 14,000 studies, is the most comprehensive summary to date of the physical science of climate change. It will be a focal point when diplomats gather in November at a U.N. summit in Glasgow to discuss how to step up their efforts to reduce emissions.
这份以1.4万多项研究为基础、已得到195个国家政府批准的报告，是对气候变化的自然科学迄今为止最全面的总结。今年11月外交官们聚集在格拉斯哥联合国气候峰会上讨论如何加大减排力度时，该报告将成为一个焦点。
A growing number of world leaders, including President Biden, have endorsed the goal of limiting global warming to 1.5 degrees Celsius, though current policies in the major polluting countries are still far off-track from achieving that target. The 10 biggest emitters of greenhouse gases are China, the United States, the European Union, India, Russia, Japan, Brazil, Indonesia, Iran and Canada.
越来越多的世界各国领导人，包括拜登总统，已经公开支持将全球变暖升温控制在1.5摄氏度以下的目标，尽管主要碳排放国家目前的政策与实现这一目标仍有很大差距。全球十大温室气体排放者分别是中国、美国、欧盟、印度、俄罗斯、日本、巴西、印度尼西亚、伊朗和加拿大。
The new report leaves no doubt that humans are responsible for global warming, concluding that essentially all of the rise in global average temperatures since the 19th century has been driven by nations burning fossil fuels, clearing forests and loading the atmosphere with greenhouse gases like carbon dioxide and methane that trap heat.
这份新报告毫无疑问地指出，人类对全球变暖负有责任，报告得出结论，自19世纪以来，全球平均气温的上升基本上都是由各国燃烧化石燃料、砍伐森林造成的，这些活动向大气中排放了二氧化碳和甲烷等吸收热量的温室气体。
The changes in climate to date have little parallel in human history, the report said. The last decade is quite likely the hottest the planet has been in 125,000 years. The world’s glaciers are melting and receding at a rate “unprecedented in at least the last 2,000 years.” Atmospheric levels of carbon dioxide have not been this high in at least 2 million years.
报告说，迄今为止的气候变化在人类历史上几乎没有过类似的情况。过去十年很可能是地球12.5万年来最热的十年。世界上的冰川正在以“至少是过去2000年间前所未有的”速度融化和消退。大气中的二氧化碳浓度在至少200万年里没有这么高过。
Ocean levels have risen 8 inches on average over the past century, and the rate of increase has doubled since 2006. Heat waves have become significantly hotter since 1950 and last longer in much of the world. Wildfire weather has worsened across large swaths of the globe. Bursts of extreme heat in the ocean — which can kill fish, seabirds and coral reefs — have doubled in frequency since the 1980s.
海平面已在过去一个世纪里平均上升了20厘米，上升的速度自2006年以来已翻了一番。自1950年以来，热浪已变得越来越热，在世界大部分地区持续的时间也更长。导致野火发生的天气在全球大部分地区越来越糟。自20世纪80年代以来，能导致鱼类、海鸟和珊瑚礁死亡的海洋极端高温爆发的频率增加了一倍。
In recent years, scientists have also been able to draw clear links between global warming and specific severe weather events. Many of the deadly new temperature extremes the world has seen — like the record-shattering heat wave that scorched the Pacific Northwest in June — “would have been extremely unlikely to occur without human influence on the climate system,” the report says. Greenhouse gas emissions are noticeably making some droughts, downpours and floods worse.
近年来，科学家们已经能在全球变暖与具体恶劣天气事件之间建立明确的联系。报告说，世界上已经看到的许多致命的新温度记录——比如今年6月席卷了美国西北太平洋地区的打破记录的热浪——“如果没有人类对气候系统的影响，是极不可能发生的”。温室气体排放已明显地使一些干旱、暴雨和洪水变得更严重。
Tropical cyclones have likely become more intense over the past 40 years, the report said, a shift that cannot be explained by natural variability alone.
报告说，热带气旋可能已在过去40年里变得更强烈，这种变化不能仅用自然界的可变性来解释。
And as global temperatures keep rising, the report notes, so will the hazards. Consider a dangerous heat wave that, in the past, would have occurred just once in a given region every 50 years. Today, a similar heat wave can be expected every 10 years, on average. At 1.5 degrees Celsius of global warming, those heat waves will strike every 5 years and be significantly hotter. At 4 degrees of warming, they will occur nearly annually.
报告指出，随着全球气温继续上升，危害也将继续加大。例如，危险的热浪袭击在某个特定地区过去可能每50年发生一次。类似的热浪现在预期平均每10年发生一次。当全球变暖1.5摄氏度时，这种热浪袭击将是每五年一次，而且明显会感觉更热。当升温达到4度时，热浪基本每年都会发生。
Or take sea level rise. At 1.5 degrees of warming, ocean levels are projected to rise another 1 to 2 feet this century, regularly inundating many coastal cities with floods that in the past would have occurred just once a century. But if temperatures keep increasing, the report said, there is a risk that the vast ice sheets in Antarctica and Greenland could destabilize in unpredictable ways, potentially adding another three feet of sea-level rise this century in the worst case.
或者以海平面上升为例。如果平均气温上升1.5度，海平面预计会在本世纪再上升30至60厘米，许多沿海城市将更频繁地被以前是百年一遇的洪水淹没。报告说，但如果气温继续上升，会出现南极洲和格陵兰岛的巨大冰盖以不可预测的方式解体的风险，导致在最糟糕情况下，海平面在本世纪可能再上升将近1米。
Further unpredictable changes may be in store. For example, a crucial ocean circulation system in the Atlantic Ocean, which helps stabilize the climate in Europe, is now starting to slow down. While the panel concluded with “medium confidence” that the system was unlikely to collapse abruptly this century, it warned that if the planet keeps heating up, the odds of such “low likelihood, high impact outcomes” would rise.
更多不可预测的变化可能会发生。例如，大西洋中一个有助于稳定欧洲气候的至关重要的海洋环流系统，如今正在开始放缓。虽然专门委员会的结论是，有“中等信心”认为这个系统不太可能在本世纪突然崩溃，但委员会警告，如果地球继续升温，出现这种“小概率、大影响后果”的可能性将会增加。
“It’s not like we can draw a sharp line where, if we stay at 1.5 degrees, we’re safe, and at 2 degrees or 3 degrees it’s game over,” said Robert Kopp, a climate scientist at Rutgers University who helped write the report. “But every extra bit of warming increases the risks.”
“不是说我们可以划出一条明确的界线，如果变暖保持在1.5度，我们就安全，如果上升到2或3度的话，一切都完了，”帮助撰写这份报告的罗格斯大学(Rutgers University)气候科学家罗伯特·柯普(Robert Kopp)说。“但变暖每额外增加一点，都会增加风险。”
Experts have estimated that current policies being pursued by world governments will put the world on track for roughly 3 degrees Celsius of warming by the end of the century. That has ramped up pressure on countries to make more ambitious pledges, beyond what they agreed to under an international climate agreement struck in Paris in 2015.
专家估计，世界各国政府目前推行的政策将使全球气温在本世纪末上升大约3摄氏度。这给各国带来了更大压力，做出超过它们2015年在巴黎达成国际气候协定时同意的力度更大的承诺。
If nations follow through on more recent promises — like Mr. Biden’s April pledge to eliminate America’s net carbon emissions by 2050 or China’s vow to become carbon neutral by 2060 — then something closer to 2 degrees Celsius of warming might be possible. Additional action, such as sharply reducing methane emissions from agriculture and oil and gas drilling, could help limit warming below that level.
如果各国能够兑现它们最近的承诺，如拜登今年4月宣布的美国不迟于2050年实现净零排放，或中国在2060年实现碳中和的誓言，那也许有可能将变暖控制在接近2摄氏度。进一步的措施，比如大幅减少农业、以及石油和天然气钻探产生的甲烷排放，或有助于将升温控制在2摄氏度之下。
“The report leaves me with a deep sense of urgency,” said Jane Lubchenco, deputy director of the White House Office of Science and Technology Policy. “Now is the critical decade for keeping the 1.5 target within reach.”
“这份报告给我留下了深深的紧迫感，”白宫科技政策办公室(White House Office of Science and Technology Policy)副主任简·卢布琴科(Jane Lubchenco)说。“现在是仍可实现1.5度目标的关键十年。”
While the broad scientific understanding of climate change has not changed drastically in recent years, scientists have made several key advances. Computer models have become more powerful. And researchers have collected a wealth of new data, deploying satellites and ocean buoys and gaining a clearer picture of the Earth’s past climate by analyzing ice cores and peat bogs.
虽然对气候变化的一般性科学认识近年来没有什么巨大改变，但科学家在几个方面取得了关键进展。计算机模型已变得更加强大。研究人员已通过卫星和海洋浮标体收集到了大量新数据，并通过分析冰芯和泥炭沼对地球以前的气候获得了更清晰的了解。
That has allowed scientists to refine their projections and conclude with greater precision that Earth is likely to warm between 2.5 degrees and 4 degrees Celsius for every doubling of the amount of carbon dioxide in the atmosphere.
这让科学家们能够改进他们的预测，得出准确度更高的结论，即大气中二氧化碳浓度每增加一倍，地球的温度就有可能上升2.5到4摄氏度。
The new report also explores in greater detail how global warming will affect specific regions of the world. For example, while only one corner of South America to date has had a detectable rise in droughts that can harm agriculture, such damaging dry spells are expected to become much more common across the continent if global average temperatures increase by 2 degrees Celsius.
这份新报告也更详细地探讨了全球变暖将给世界上的具体地区造成怎样的影响。例如，迄今为止只在南美洲的一个角落出现了可觉察到的旱灾加剧危害农业的情况，如果全球平均气温上升2摄氏度，这种破坏性的旱灾预计将在整个南美大陆变得更普遍。
The focus on regional effects is one of the most important new aspects of this report, said Valérie Masson-Delmotte, a climate scientist at University of Paris-Saclay and a co-chair of the group that produced the report. “We show that climate change is already acting in every region, in multiple ways,” she said.
聚焦对地区的影响是该报告最重要的新方面之一，巴黎-萨克雷大学(University of Paris-Saclay)气候科学家、报告撰写小组的联合组长瓦莱丽·马森-德尔莫特(Valérie Masson-Delmotte)说。“我们向人们展示，气候变化已以多种方式对每个地区产生影响，”她说。
Past climate reports have focused mainly on large-scale global changes, which has made it hard for countries and businesses to take specific steps to protect people and property. To help with such planning, the panel on Monday released an interactive atlas showing how different countries could be transformed as global temperatures rise.
以前的气候报告主要关注大范围的全球变化，这让各国和各个企业难以采取具体措施保护人民和财产。为了帮助人们作出具体的规划，专门委员会周一发布了交互式地图，向人们展示了随着全球气温上升，不同国家可能发生的变化。
“It’s very critical to provide society, decision makers and leaders with precise information for every region,” Dr. Masson-Delmotte said.
“为每个区域的社会、决策者和领导人提供准确的信息至关重要，”马森-德尔莫特说。
The new report is part of the sixth major assessment of climate science from the Intergovernmental Panel on Climate Change, which was created in 1988. A second report, set to be released in 2022, will detail how climate change might affect aspects of human society, such as coastal cities, farms or health care systems. A third report, also expected next year, will explore more fully strategies to reduce greenhouse gas emissions and halt global warming.
这份新报告是1988年成立的政府间气候变化专门委员会对气候科学做的第六次主要评估的一部分。第二份将于2022年发布的报告，将详细描述气候变化可能影响人类社会的哪些方面，比如沿海城市、农场或医疗保健系统。第三份报告预计也将于明年发布，将更全面地探索减少温室气体排放、遏制全球变暖的应对策略。
