Low-Energy Fridays: Climate Change Is—and Is Not—an Existential Risk

The 2023 United Nations Climate Change Conference is over, but undercurrents of existential anxiety persist. This is a timely reminder that climate policy begins with characterizing the problem correctly. Perhaps no frame has been more hotly debated—and misunderstood—than whether climate change poses an existential risk. As this week’s title reveals, the answer is not definitive. But understanding the circumstances under which climate change is and is not an existential risk has profound bearing on whether our policy response benefits or harms humanity.

An existential risk threatens the existence of a subject, such as a community, a nation state, or even humanity as a whole. In this sense, climate change does present such a risk to certain communities or nation states, such as low-lying island countries susceptible to sea-level rise. Climate change is, to a degree, a matter of life or death, considering how it may shift mortality patterns around the world. But there is no evidence that humanity’s existence is at stake. However, climate change is existential to an alarming proportion of Earth’s species—with up to half facing extinction.

We can learn much from the history of the human condition under previous climate eras. Paleoclimate data reveal that climatic fluctuations markedly affected human evolution and perhaps eliminated some human populations up to continental scale a million years ago. Overall, however, primitive humans proved resilient under a variety of harsh climatic conditions. In fact, the collapse of the Atlantic meridional overturning circulation current—arguably the biggest climate risk in the news today— previously occurred about 14,500 years ago.

This is not to understate the threat that human-caused climate change presents, but simply to put it in perspective. There are scenarios of climate “tail events” that could accelerate climatic disruption and induce massive economic, social and ecological damages. Yet there is no scenario in which humanity would not be able to provide the bulk of its basic needs, especially with further technological advances.

Distinguishing the circumstances of existential climate risk is not just semantically important—it is crucial for better civil society dialogue, policy analysis and decisions. Importantly, policies to mitigate climate change only improve society if their benefits exceed their costs.

An existential threat to humanity warrants virtually any intervention to reduce the risk. For example, if a civilization-destroying asteroid were hurtling toward Earth, any price tag to neutralize the threat would be worth it. Climate change is often mischaracterized in this way, as it was by President Joe Biden earlier this year. Some cultural analogies even use the asteroid metaphor literally, as in the movie Don’t Look Up.

Such discourse encourages policy interventions irrespective of their cost and ignores the value of adaptation. A variety of interventions like fossil fuel bans and green subsidies now impose costs that exceed their climate benefits, whereas market-based policies would reduce emissions at costs below benefits. Economical policies that improve adaptation in vulnerable areas like Florida must be prioritized in order to minimize human suffering.

Policymaking should account for the ways in which climate change is existential. The existence value of species and cultural heritage is remarkably difficult to quantify, but we must try. Our failure to do so understates the economical case for climate mitigation. In the end, we need a confident range of value for climate mitigation to determine the cost at which these policies benefit or harm society.

Policies should maximize the combination of future wealth and environmental quality if they are to benefit posterity. This requires mitigating climate change aggressively, but also cost-consciously. And that begins with framing climate risk accurately.