Could Climate Change Make Humans Go Extinct?气候变化会让人类灭绝吗？

帕特里克·佩斯特　陈天怡/译

The impacts of climate change are here with soaring temperatures， stronger hurricanes， intensified floods and a longer and more severe wildfire season. Scientists warn that ignoring climate change will yield “untold suffering” for humanity. But if things are going to get that much worse， could climate change make humans go extinct？

气候变化的影响已然显现：气温飙升，飓风增强，洪水加剧，野火季时间更长、火势更猛。科学家警告，忽视气候变化将会带给人类“无尽的苦难”。不过，如果情况真的进一步恶化，人类会因气候变化灭绝吗？

If we just consider the direct impacts， its unlikely to cause our extinction. However， its possible that climate change will still threaten the lives of hundreds of millions of people， such as by leading to food and water scarcity， which has the potential to trigger a societal collapse and set the stage for global conflict， research finds.

仅就直接影响而言，气候变化不太可能导致人类灭绝。但研究发现，气候变化会造成食物和水的短缺等问题，可能引起社会崩溃，为全球冲突埋下隐患，从而威胁数亿人的生命。

Too hot to handle？

过热危机？

Humans are increasing the amount of greenhouse gases， such as carbon dioxide and methane， in the atmosphere through the burning of fossil fuels and other activities. These gases trap and hold heat from the sun， causing global temperatures to rise and the climate to change much faster than it otherwise would， putting humanity on a dangerous path.

由于燃烧化石能源和其他人类活动，大气中二氧化碳和甲烷等温室气体的含量正在上升。这些气体吸收并储存来自太阳的热量，导致全球气温升高，气候变化远快于正常速度，置人类于险境。

A runaway greenhouse effect is probably the only way climate change impacts could directly cause human extinction， according to Luke Kemp， a research associate at the Centre for the Study of Existential Risk1 at the University of Cambridge in the United Kingdom. This effect happens when a planet is caught in an unstoppable， positive feedback loop2 of warming and absorbs more heat than it loses， until the planets oceans evaporate and it can no longer sustain life.

英國剑桥大学存在风险研究中心的助理研究员卢克·肯普称，“失控温室效应”或许是气候变化能够直接造成人类灭绝的唯一途径。该效应指行星陷入无法遏制的正反馈变暖循环，吸热多于散热，直到海洋蒸发，没有生命可以存活。

Fortunately， the runaway greenhouse effect is not a plausible climate change scenario on Earth. For the effect to occur， a planet needs carbon dioxide levels of a couple of thousand parts per million3 （Earth has a little over 400 parts per million） or a huge release of methane， and there isnt evidence for that at this time， Brian Kahn， a research scientist at NASAs Jet Propulsion Laboratory， told NASA in 2018.

值得庆幸的是，失控温室效应不太可能在地球上发生。美国国家航空航天局（NASA）喷气推进实验室的研究员布赖恩·卡恩2018年告诉NASA，发生失控温室效应需要行星上的二氧化碳浓度达到数千ppm（地球的二氧化碳浓度略高于400ppm）或甲烷大量释放，而目前还没有相关迹象。

According to Michael Mann， a distinguished professor of atmospheric science， a global temperature increase of 5.4 degrees Fahrenheit （3 degrees Celsius） or more could lead to a collapse of our societal infrastructure and massive unrest and conflict， which， in turn， could lead to a future that resembles some Hollywood dystopian4 films.

著名大氣科学教授迈克尔·曼称，全球气温上升5.4华氏度（3摄氏度）或更多，就可能导致社会基础设施崩溃和大规模动乱冲突，进而令世界陷入某些好莱坞反乌托邦电影所描述的未来。

One way climate change could trigger a societal collapse is by creating food insecurity. Warming the planet has a range of negative impacts on food production， including increasing the water deficit and thereby reducing food harvests， Live Science5 previously reported. Food production losses can increase human deaths and drive economic loss and socio-political instability， among other factors， that may trigger a breakdown of our institutions and increase the risk of a societal collapse， according to a study published in the journal Climatic Change.

气候变化可能造成粮食短缺，由此引发社会崩溃。生活科学网站曾报道，地球变暖会对粮食生产造成诸多负面影响，如加剧水资源短缺，从而减少粮食收成。发表于《气候变化》期刊的一份研究报告表明，粮食产量降低会导致更多人死亡，造成经济损失和社会政治不稳定等后果，最终可能引起体制瓦解，增加社会崩溃的风险。

Past extinctions and collapses

历史上的灭绝与崩溃

Kemp studies previous civilization collapses and the risk of climate change. Extinctions and catastrophes almost always involve multiple factors， he said， but he thinks if humans were to go extinct， climate change would likely be the main culprit6.

肯普的研究对象是历史上的文明崩溃和气候变化的风险。他说，灭绝事件和重大灾害往往牵涉多重因素，但他认为，如果人类真的走向灭绝，气候变化很有可能是罪魁祸首。

All of the major mass-extinction events in Earths history have involved some kind of climatic change， according to Kemp. These events include cooling during the Ordovician-Silurian extinction about 440 million years ago that wiped out 85% of species， and warming during the Triassic-Jurassic extinction about 200 million years ago that killed 80% of species， Live Science previously reported.

肯普称，地球历史上所有重大的集群灭绝事件都与某种形式的气候变化有关。根据生活科学网站的报道，在约4.4亿年前的奥陶纪—志留纪大灭绝中，地球变冷导致85%的物种消失；在约2亿年前的三叠纪—侏罗纪大灭绝中，地球变暖造成80%的物种死亡。

And more recently， climate change affected the fate of early human relatives. Scientists dont know why Neanderthals7 went extinct about 40，000 years ago， but climatic fluctuations seem to have broken their population up into smaller， fragmented groups， and severe changes in temperature affected the plants and animals they relied on for food， according to the Natural History Museum in London. Food loss， driven by climate change， may have also led to a tiny drop in Neanderthal fertility rates， contributing to their extinction， Live Science previously reported.

更晚一些，气候变化影响了早期人类近亲的命运。科学家尚不清楚约4万年前尼安德特人灭绝的原因，但伦敦自然历史博物馆的资料显示，气候波动似乎将其人口分割成了规模较小且分散的族群，同时气温剧变影响了他们赖以维生的动植物。生活科学网站曾报道，气候变化导致的食物減少可能还造成尼安德特人的生育率小幅下降，进一步推动了其灭绝。

Climate change has also played a role in the collapse of past human civilizations. A 300-year-long drought， for example， contributed to the downfall of ancient Greece about 3，200 years ago. But Neanderthals disappearing and civilizations collapsing do not equal human extinction. After all， humans have survived climate fluctuations in the past and currently live all over the world despite the rise and fall of numerous civilizations.

气候变化在史上人类文明的崩溃中也发挥了作用。例如，约3200年前，一场长达300年的干旱加剧了古希腊文明的衰落。不过，尼安德特人消失和各个文明崩塌不等于人类灭绝。毕竟，尽管经历了无数文明的兴衰，人类还是安然度过了一次次气候波动，现今遍布全球。

Today， we live in a global， interconnected civilization， but theres reason to believe our species could survive its collapse. A study published in the journal Sustainability identified countries most likely to survive a global societal collapse and maintain their complex way of life. Five island countries， including New Zealand and Ireland， were chosen as they could remain habitable through agriculture， thanks to their relatively cool temperatures， low weather variability and other factors that make them more resilient to climate change.

今天，我们处在全球化且相互关联的文明之中，但仍有理由相信，人类可以承受这一文明的分崩离析。《可持续发展》期刊发表了一份研究报告，报告中列举了全球社会崩溃后最有可能幸存并延续其复杂生活方式的国家，包括新西兰和爱尔兰在内的五个岛国榜上有名。得益于气温较低和天气稳定等因素，这些国家对气候变化的适应能力更强，可以通过农业维持宜居环境。

So， even if climate change triggers a global civilization collapse， humans will likely be able to keep going， at least in some areas.

因此，即使气候变化引发全球文明崩溃，人类仍有可能繁衍生息，至少在某些地区如此。

Turning on8 ourselves

自相残杀

The last scenario to consider is climate-driven conflict. Kemp explained that in the future， a scarcity of resources that diminish because of climate change could potentially create conditions for wars that threaten humanity. “There are reasons to be concerned that as water resources dry up and scarcity becomes worse， and the general conditions of living today become much， much worse， then suddenly， the threat of potential nuclear war becomes much higher，” Kemp said.

最后，气候变化引起的冲突也是需要考虑的情形。肯普解释道，气候变化将进一步减少稀缺的资源，可能会为威胁人类生存的战争创造条件。他说：“值得担忧的是，随着水资源枯竭、稀缺性加剧，整体的生存条件相较当前大幅度恶化，潜在核战争的可能性将会骤增。”

A 2019 study published in the journal Science Advances found that a nuclear conflict between just India and Pakistan， with a small fraction of the worlds nuclear weapons， could kill 50 million to 125 million people in those two countries alone. Nuclear war would also change the climate， such as through temperature drops as burning cities fill the atmosphere with smoke， threatening food production worldwide and potentially causing mass starvation.

《科学进展》期刊2019年发表了一份研究报告，该研究发现，仅印度和巴基斯坦之间的核冲突——两国所拥有的核武器仅占世界总量的一小部分——就可能造成两国5000万到1.25亿人口死亡。核战争还会改变气候，比如城市燃烧产生的烟尘充满大气，导致气温下降，威胁全球粮食生产，可能带来大规模饥荒。

Whats next？

路在何方？

While avoiding complete extinction doesnt sound like much of a climate change silver lining9， there is reason for hope. Experts say it isnt too late to avoid the worst-case scenarios with significant cuts to greenhouse gas emissions.

气候变化不会让人类完全灭绝，这听起来并不令人寬慰，但希望确实尚存。专家称，大幅削减温室气体排放为时未晚，可以避免最糟糕的情形。

“It is up to us，” Mann said. “If we fail to reduce carbon emissions substantially in the decade ahead， we are likely committed to a worsening of already dangerous extreme weather events， inundation10 of coastlines around the world due to melting ice and rising sea level， more pressure on limited resources as a growing global population competes for less food， water and space due to climate change impacts. If we act boldly now， we can avoid the worst impacts.”

“这取决于人类自身。”曼说，“如果未来十年人类不能大量减少碳排放，已然危险重重的极端天气事件恐将继续恶化，全球的海岸线会因冰川融化和海平面上升而被淹没，不断增长的全球人口将争夺由于气候变化而减少的粮食、水和空间，使有限的资源面临更大压力。如果现在果断行动，就能避免最糟糕的后果。”