Event summary by Luke Hatton

“Climate Emergency” was declared as the word of the year in 2019 by Oxford Dictionaries, as the phrase’s popularity soared from relative obscurity into one of the most prominent terms of the year. Scientists have known for decades that climate change poses a significant threat to the world and society, but 2019 seemed to represent a shift in awareness of the urgency of the situation in the mind of the wider world. 
 
There’s no doubt about it—the situation is dire, and action must be taken swiftly if we are to limit climate change to the ‘safe’ level of 1.5 degrees Celsius. But does climate change really represent a ‘major threat to civilisation’, in the words of the 2020 Doomsday Clock Statement? Does it merit moving the minute hand of the Doomsday Clock (a measure of threats to humanity and the planet, founded in 1945 by scientists who helped develop the first atomic weapons) closer to the midnight apocalypse than ever? 
 
We invited three expert panellists, David Wallace-Wells, Zeke Hausfather and Luke Kemp, to shed some light on whether climate change truly poses an existential risk to human life as we know it. 
 
David Wallace-Wells
David is the Deputy Editor of New York magazine, where he writes frequently about climate change and the near future of technology. His cover story from July 2017, surveying the landscape of worst-case scenarios for global warming, became the most-read story the magazine has ever published, and his book on this topic, The Uninhabitable Earth, is a Sunday and New York Times Bestseller. 
 
Primarily, David said he viewed the question of whether climate change poses an existential risk as more of a semantic question; it really does depend on what you mean by the word existential. Practically speaking, he doesn’t think that the threats some climate activists warn of, such as civilisational collapse over the course of the century, are likely. 
 
In some regions, there will be—and indeed there already is—a literal threat to existence due to climate change, with many people dying from climate-related catastrophes. He warns that we have already reached a level of warming today—estimated at over 1℃ above pre industrial levels—where our lives and our society are being shaped by these forces, with increased risk of droughts, hurricanes and mass migration already being seen as a result of climate change. Practically speaking, a 2℃ rise from pre-industrial levels is the best possible outcome we can hope for, but even this could result in hundreds of millions of climate refugees, an additional 150m deaths from air pollution, and summer temperatures that cause heat death or stroke in some regions.
 
Political institutions will be challenged in ways that require us to renovate, reform or rebuild them to cope with this 2℃ world, David added, with the shape of life in a time of intense climate change depending not only on the physical warming, but the institutions we build and the protections we put in place to support human flourishing. To some degree, the nature of our existence will be preserved, but the lives of our children and grandchildren may well be unrecognizable. 
 
We are very far from the curtains coming down and all life on Earth ending from climate change, but we are fooling ourselves by thinking about this in binary terms. We live in a world transformed by global warming and have the opportunity to shape the future of all human life on the planet by choosing to adapt and respond today. Our existence is already being shaped by the climate—the question we must act to answer is how far along that spectrum we will fall. 
 
Zeke Hausfather
Zeke is a climate scientist and energy systems analyst whose research focuses on observational temperature records, climate models and mitigation technologies. He has spent 10 years working in the cleantech sector, and currently is the Director of Climate and Energy at the Breakthrough Institute and the US analyst for Carbon Brief.
 
Zeke began by suggesting that we can all agree that climate change isn’t going to cause the extinction of the human race. Humanity is a remarkably adaptable species, and has spread to the most extreme environments on the planet. However, climate change can and will have a huge impact on society, and could act as an existential risk multiplier, amplifying the impact of other shocks to society, he warned. 
 
The work being done in the lead up to the next report from the International Panel on Climate Change (IPCC) is dividing the ability to adapt to climate change and the magnitude of climate change itself into separate scenarios so the two can be compared. As it turns out, Zeke explained, the worst case for climate change is not necessarily the one with the most warming. The worst case will be a world that is relatively poor and unequal, rife with nationalism, isolationism and conflict, coupled with a high degree of warming. This is a world where institutions and governments are weak, and where climate change could tip civilisations into collapse. Echoing David’s point, he explained that the strength of society and institutions will play a strong role in whether climate change can pose an existential risk. 
 
However, Zeke warned of the risk of framing climate change in terms of extinction, as this can be reductive and lead to doom-ism with regard to climate action. Scientists now argue more with doom-ists than climate sceptics, and defeatism around climate change is dangerous.
 
From a scientific perspective, there is certainly a lot that is unknown about climate systems, but the best models do not tend to indicate a strong significance for tipping points (that is, the risk of reaching a level of warming that sets off a domino effect of positive feedback, significantly raising the warming past the initial level), at least on a global scale. Global warming is largely a function of cumulative emissions, a pretty linear relationship—certainly not containing a strong tipping point that could turn the climate crisis into a climate catastrophe.  
 
Overall, the world certainly isn’t moving in the direction we need fast enough, Zeke said, but it has come far in the last two decades. 20 years ago it looked quite possible that emissions would double or even triple by the end of the century, while ten years ago China was building a coal-fired power station every two days. Ten years later, in 2013, global coal peaked, and has fallen ever since, while renewables are increasingly becoming the cheapest form of energy in many places. We’re moving towards a ‘muddling through’ world right now, where we’re avoiding 4-5℃ but are very far from the best case outcome of 1-2℃. This will be catastrophic for some human and natural systems but it is less likely to pose an existential threat to society than the unconstrained world we were on track for. 
 
Luke Kemp
Luke is a Research Associate with the Cambridge Centre for the Study of Existential Risk, where he looks at past civilisation collapses to guide present policy. He is also an honorary lecturer in environmental policy at the Australian National University (ANU), holds a PhD in international relations and was previously a senior economist at Vivid Economics.
 
The blunt answer, Luke began, is that climate change does pose an existential threat. Above three degrees of warming we are running in the dark, and have to rely on geological records to work out what could happen. There is a lack of interest amongst scientists in looking at the outcomes for large temperature increases and worst case scenarios, as people tend to err on the side of the least drama. Unfortunately, there is not enough information to base conclusions on.
 
It's useful to define what an existential risk is when examining it with regard to climate change, Luke explained. Professor Nick Bostrom defines it as the annihilation of earth-originating intelligent life and/or permanent drastic curtailment of human potential. The easy way to think about this is to think of a global civilisation collapse, with the destruction of most critical systems, the failure of many states and drastic loss of social complexity. With a 2℃ rise, already most atoll and small islands nations are likely to become uninhabitable. 
 
Luke set out four reasons why we can consider climate change as an existential risk;

1. Precedence - all five of the last great extinction events have involved some form of climate change over the last 540m years. The Great Permian Die Off was probably in the region of 8℃, with roughly 90% of the biosphere becoming extinct. However, this event took place over 200,000 years; anthropogenic climate change is happening at a much faster rate. Climactic change has also contributed to the collapse of historical human civilisations, including the Hittites, the lowland Maya, and the Western Roman Empire. However, it was very rare for the climate to be the only stressing factor, echoing the multiplier effect first brought to the discussion by Zeke.
2. Humans are adapted to a very particular climate niche. A recent paper from the National Academy of Sciences estimated this niche to be one with a mean average temperature of 13 degrees, which was also determined to be the optimum level for economic growth.
3. The second order effects of climate change will be much worse in a world rife with inequality, conflict and weak institutions. Conflict already happens in areas with existing ethnic divisions, and climate will act as a stressor. There are good reasons to think that climate change will have knock on effects that make the world a worse place.
4. The occurrence of another event which shocks civilisation, such as nuclear winters or super-volcano eruptions, could combine with climate change to create the ‘perfect storm’ that could lead to civilisational collapse. 

 
Given the unknowns and uncertainties with regard to climate change - it would be bad risk management to not think about the worst case scenario, Luke concluded.
 
To hear a more in-depth examination of the question of whether climate change poses an existential risk, and to hear the answers to the questions posed by the audience, head to our YouTube channel, where a copy of the panel discussion has been uploaded: https://www.youtube.com/watch?v=ah1pLU10o_U. 

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