We know that climate change is a major threat to the world, but is it a global catastrophic risk? This GCRI video addresses the question by studying three extreme climate change scenarios and comparing them to the definition of global catastrophic risk. It covers extreme warming, geoengineering failure, and pandemics induced by climate change.
The video is part of a series of GCRI videos designed to help people learn some fundamentals of global catastrophic risk. Climate change is a great topic for learning about the definition of global catastrophic risk and some other fundamentals such as how to analyze catastrophe scenarios and how to account for uncertainty about the scenarios.
The video is loosely based on the GCRI research paper Climate change, uncertainty, and global catastrophic risk. Other notable studies of climate change and global catastrophic risk from outside of GCRI include Assessing climate change’s contribution to global catastrophic risk and Climate endgame: Exploring catastrophic climate change scenarios.
To get involved, see the GCRI Advising and Collaboration Program, in particular the 2025 Open Call for Advisees and Collaborators. Also consider subscribing to the monthly GCRI newsletter and making a donation. Please also subscribe to the GCRI YouTube channel and share our videos with other people who may be interested.
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References and source material:
0:00 – New York City high temperature of 97ºF on 29 July 2025: Accessible via the US National Centers for Environmental Information (it may take some clicking around to get the exact date and location).
0:07 – The all-time high temperature for New York City on 29 July is listed as 99ºF degrees F in 1949.
1:10 – Definitions of global catastrophic risk are compiled and discussed in various GCRI research papers including this, this, this, and this.
2:54 – The data on the times and places where agriculture was invented is from Figure 1 of the paper The nature of selection during plant domestication. This lists 24 separate instances in which agriculture was invented, one of which (4b in Figure 1) is not included in the video due to insufficient documentation. 24 separate instances is on the high side, and the paper acknowledges that some of them may not be independent—the historical record is inconclusive. However, while other studies may find fewer instances, all of them clearly show that agriculture was independently invented multiple times within the last 12,000 years. That fundamental point is not in dispute.
2:58 – The map is from the US Central Intelligence Agency’s World Factbook via Wikimedia Commons.
3:14 – The theory that climate explains why agriculture was only invented within the last 12,000 years is presented in the papers Was agriculture impossible during the Pleistocene but mandatory during the Holocene? A climate change hypothesis and Origin of agriculture and domestication of plants and animals linked to early Holocene climate amelioration.
3:20 – The historical temperature is from this graph based on a 2004 EPICA Antarctic ice core study. More recent studies may show some differences, for example this 2020 study showing no more than 2ºC warming around 120,000 years ago, whereas the EPICA data show around 4ºC warming. This specific difference is a cause for some concern about the current climate change situation: if humans lived through 4ºC warming 120,000 years ago, that shows we have more resilience to warming than if it was only 2ºC.
3:25 – The animation of quirks in Earth’s orbit is from NASA.
3:32 – The two planet images are both from NASA via Wikimedia Commons: Mars and Jupiter.
3:37 – The term “ice age” is commonly used in two different ways. One is for the colder periods that occur roughly every 100,000 years. This is how the term is used in the video. However, the scientific community would typically refer to these periods as “glacials” because these are periods in which glaciers are expanding, in contrast with warmer “interglacials” when glaciers are shrinking. The scientific community typically uses the term “ice age” for the much longer periods of time when there are glaciers covering at least parts of Earth’s surface. By that definition, Earth is currently in an ice age. For further discussion, see e.g. the ice age article on Wikipedia.
4:06 – The projections of future temperatures through 2300 are from Figure 4.40a of the IPCC AR6 WG1 Ch.4.
4:18 – The planet has warmed by about 1ºC since before the industrial revolution—for documentation, see for example this.
4:34 – The map is based on Figure 1f of the 2010 paper An adaptability limit to climate change due to heat stress. Figure 1f shows a simulation of the maximum “wet bulb” temperature in a scenario of warming of 12ºC. Wet bulb temperature is a combination of temperature and humidity. As the paper discusses, if temperatures go above a certain threshold of wet bulb temperature, humans and other mammals (and possibly also birds) lose the ability to maintain a cool enough body temperature and they overheat and die. The paper put the threshold at 35ºC. A more recent paper took a closer look and found lower thresholds, with some variation depending on humidity, but generally at around 30ºC. For related discussion, see e.g. this, this, and this. Therefore, in the map in the video, the green regions are the areas that stay below 30ºC in Figure 1f of the 2010 paper. The boundary curves shown in the video are hand traced and may not be precise, but the important part is the overall trend, in which only select locations may be livable year-round.
4:44 – Warming of 12ºC is on the high side of what might happen, and if it does, it may take centuries to reach—for documentation, see Figure 4.40a of the IPCC AR6 WG1 Ch.4.
6:00 – The systematic underrepresentation of extreme warming scenarios in climate change research is documented in the papers Betting on the best case: Higher end warming is underrepresented in research and Focus of the IPCC Assessment Reports Has Shifted to Lower Temperatures.
7:36 – Critique of the term “existential risk” can be found in the GCRI research paper Climate change, uncertainty, and global catastrophic risk. Related discussion appears in a GCRI review of the book The Precipice.
8:06 – The GCRI definition of global catastrophic risk as the risk of an event that could significantly harm or even destroy human civilization at the global scale—this is found, for example, on the GCRI website page About Global Catastrophic Risk.
9:24 – The risk of geoengineering catastrophe if people stop putting particles into the stratosphere is analyzed in the GCRI paper Double catastrophe: Intermittent stratospheric geoengineering induced by societal collapse and the more recent paper A fate worse than warming? Stratospheric aerosol injection and global catastrophic risk.
10:20 – The projections of future temperatures through 2100 are from Figure SPM.8a of the IPCC AR6 WG1 SPM. As the figure shows, it remains possible to avoid 2ºC warming. However, this may require substantial reductions in greenhouse gas emissions, which is not the current trajectory.
10:37 – The effect of climate change on pandemics is discussed, for example, in the recent research paper Climate change increases cross-species viral transmission risk. See also this and this.
10:45 – Zoonosis is the leading theory for how COVID-19 started—see for example the GCRI research paper The origin and implications of the COVID-19 pandemic: An expert survey.
11:15 – The spread of dengue fever in mainland France is documented here.
12:26 – The history of people using uncertainty about climate change (and other issues) as an excuse for inaction is documented in the book Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming.
12:35 – The idea that the uncertainty about climate change makes it more of a global catastrophic risk comes from the GCRI paper Climate change, uncertainty, and global catastrophic risk.
13:30 – Regarding the interconnections between different risks, see GCRI’s work on Cross-Risk Systems.
14:08 – Regarding the idea that the important part is not which risks are bigger, but instead what can be done to reduce the risks, see GCRI’s work on Risk & Decision Analysis. Risk analysis is about characterizing and quantifying risks, whereas decision analysis is about identifying and evaluating decision options. In practical terms, it can be argued that decisions are the important part, even while a decision-maker may take risks into account when evaluating the options. And we are all decision-makers for our own lives and activities.
15:38 – The video references the GCRI Advising and Collaboration Program, in particular the 2025 Open Call for Advisees and Collaborators.