Could Climate Change Make Humans Go Extinct?氣候變化會讓人類滅絕嗎？

帕特里克·佩斯特　陳天怡/譯

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？

氣候變化的影響已然顯現(xiàn)：氣溫飆升，颶風增強，洪水加劇，野火季時間更長、火勢更猛?？茖W家警告，忽視氣候變化將會帶給人類“無盡的苦難”。不過，如果情況真的進一步惡化，人類會因氣候變化滅絕嗎？

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.

僅就直接影響而言，氣候變化不太可能導致人類滅絕。但研究發(fā)現(xiàn)，氣候變化會造成食物和水的短缺等問題，可能引起社會崩潰，為全球沖突埋下隱患，從而威脅數億人的生命。

Too hot to handle？

過熱危機？

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.

由于燃燒化石能源和其他人類活動，大氣中二氧化碳和甲烷等溫室氣體的含量正在上升。這些氣體吸收并儲存來自太陽的熱量，導致全球氣溫升高，氣候變化遠快于正常速度，置人類于險境。

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.

英國劍橋大學存在風險研究中心的助理研究員盧克·肯普稱，“失控溫室效應”或許是氣候變化能夠直接造成人類滅絕的唯一途徑。該效應指行星陷入無法遏制的正反饋變暖循環(huán)，吸熱多于散熱，直到海洋蒸發(fā)，沒有生命可以存活。

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.

值得慶幸的是，失控溫室效應不太可能在地球上發(fā)生。美國國家航空航天局（NASA）噴氣推進實驗室的研究員布賴恩·卡恩2018年告訴NASA，發(fā)生失控溫室效應需要行星上的二氧化碳濃度達到數千ppm（地球的二氧化碳濃度略高于400ppm）或甲烷大量釋放，而目前還沒有相關跡象。

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.

著名大氣科學教授邁克爾·曼稱，全球氣溫上升5.4華氏度（3攝氏度）或更多，就可能導致社會基礎設施崩潰和大規(guī)模動亂沖突，進而令世界陷入某些好萊塢反烏托邦電影所描述的未來。

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.

氣候變化可能造成糧食短缺，由此引發(fā)社會崩潰。生活科學網站曾報道，地球變暖會對糧食生產造成諸多負面影響，如加劇水資源短缺，從而減少糧食收成。發(fā)表于《氣候變化》期刊的一份研究報告表明，糧食產量降低會導致更多人死亡，造成經濟損失和社會政治不穩(wěn)定等后果，最終可能引起體制瓦解，增加社會崩潰的風險。

Past extinctions and collapses

歷史上的滅絕與崩潰

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.

肯普的研究對象是歷史上的文明崩潰和氣候變化的風險。他說，滅絕事件和重大災害往往牽涉多重因素，但他認為，如果人類真的走向滅絕，氣候變化很有可能是罪魁禍首。

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.

肯普稱，地球歷史上所有重大的集群滅絕事件都與某種形式的氣候變化有關。根據生活科學網站的報道，在約4.4億年前的奧陶紀—志留紀大滅絕中，地球變冷導致85%的物種消失；在約2億年前的三疊紀—侏羅紀大滅絕中，地球變暖造成80%的物種死亡。

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，氣候變化影響了早期人類近親的命運?？茖W家尚不清楚約4萬年前尼安德特人滅絕的原因，但倫敦自然歷史博物館的資料顯示，氣候波動似乎將其人口分割成了規(guī)模較小且分散的族群，同時氣溫劇變影響了他們賴以維生的動植物。生活科學網站曾報道，氣候變化導致的食物減少可能還造成尼安德特人的生育率小幅下降，進一步推動了其滅絕。

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.

氣候變化在史上人類文明的崩潰中也發(fā)揮了作用。例如，約3200年前，一場長達300年的干旱加劇了古希臘文明的衰落。不過，尼安德特人消失和各個文明崩塌不等于人類滅絕。畢竟，盡管經歷了無數文明的興衰，人類還是安然度過了一次次氣候波動，現(xiàn)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，我們處在全球化且相互關聯(lián)的文明之中，但仍有理由相信，人類可以承受這一文明的分崩離析?！犊沙掷m(xù)發(fā)展》期刊發(fā)表了一份研究報告，報告中列舉了全球社會崩潰后最有可能幸存并延續(xù)其復雜生活方式的國家，包括新西蘭和愛爾蘭在內的五個島國榜上有名。得益于氣溫較低和天氣穩(wěn)定等因素，這些國家對氣候變化的適應能力更強，可以通過農業(yè)維持宜居環(huán)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，即使氣候變化引發(fā)全球文明崩潰，人類仍有可能繁衍生息，至少在某些地區(qū)如此。

Turning on8 ourselves

自相殘殺

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，氣候變化引起的沖突也是需要考慮的情形?？掀战忉尩?，氣候變化將進一步減少稀缺的資源，可能會為威脅人類生存的戰(zhàn)爭創(chuàng)造條件。他說：“值得擔憂的是，隨著水資源枯竭、稀缺性加劇，整體的生存條件相較當前大幅度惡化，潛在核戰(zhàn)爭的可能性將會驟增。”

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.

《科學進展》期刊2019年發(fā)表了一份研究報告，該研究發(fā)現(xiàn)，僅印度和巴基斯坦之間的核沖突——兩國所擁有的核武器僅占世界總量的一小部分——就可能造成兩國5000萬到1.25億人口死亡。核戰(zhàn)爭還會改變氣候，比如城市燃燒產生的煙塵充滿大氣，導致氣溫下降，威脅全球糧食生產，可能帶來大規(guī)模饑荒。

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.

氣候變化不會讓人類完全滅絕，這聽起來并不令人寬慰，但希望確實尚存。專家稱，大幅削減溫室氣體排放為時未晚，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.”

“這取決于人類自身。”曼說，“如果未來十年人類不能大量減少碳排放，已然危險重重的極端天氣事件恐將繼續(xù)惡化，全球的海岸線會因冰川融化和海平面上升而被淹沒，不斷增長的全球人口將爭奪由于氣候變化而減少的糧食、水和空間，使有限的資源面臨更大壓力。如果現(xiàn)在果斷行動，就能避免最糟糕的后果?！?/p>