Although the world is currently on track to reach between 2 and 3ºC of warming by 2100, this comes with large uncertainties, stemming from both the climate models and uncertainty about which emissions pathway the world will take. These uncertainties are themselves difficult to estimate, owing partly to the fact that climate models are designed to estimate the mean of the temperature distribution, not the tails. This implies a small but uncertain chance of an extreme level of warming, such as warming above 6ºC based on emissions up to 2100. The impacts of this level of warming are relatively unknown in comparison to lower levels, but may constitute an existential risk. High levels of warming may also provide greater incentive for some nations to unilaterally pursue geoengineering techniques, some of which come with potentially catastrophic levels of risk if mismanaged.

Furthermore, even keeping to 2-3ºC warming, there may be potential low-probability events which could threaten global food supplies, leading to global catastrophic or even existential risks. It is uncertain whether these types of events would be enough to truly create a catastrophic outcome, however the pathways to reducing the likelihood of this seem mostly focused on adaptation to these kinds of extreme weather events. As a result, potential work on this area can take many different forms, such as assessments or work to improve countries’ capacity to adapt to “black swan” extreme weather events, limits to adaptation, research on heat-resistant crops, etc.

Finally, climate change has the potential to be an accelerant or driver of other existential risks. This can mean viewing from a climate perspective risks traditionally considered “separate” from climate change, such as nuclear war, but also underappreciated consequences from the human response to climate change (e.g. societal collapse from negative feedback loops and fragilities in human systems, global instability driving governance & coordination failures, etc). As pointed out by Beard et al. (2021), the first two issues above focus excessively on global temperature rise and direct climate impacts according to climate and integrated assessment models, without taking into consideration human responses. We believe that this third area is therefore the largest in scope with the most capacity and promise for further research.

Further resources

• Assessing climate change’s contribution to global catastrophic risk, Beard et al., 2021

• Climate Change Risk Assessment: Cascading Systemic Risks - Chatham House, 2021

• Stratospheric aerosol injection research and existential risk, Halstead, 2018

• Classifying global catastrophic risks, Avin et al., 2018

For more on climate as a possible existential risk, see this document.