International risk of food insecurity and mass mortality in a runaway global warming scenario

C.E. Richards, H.L. Gauch, J.M. Allwood

Establishes that high-range global warming is understudied compared to low- to mid-range scenarios, and our modern globalised food system is uniquely vulnerable to climate change.

Provides new insights into World3’s ‘runaway global warming’ (8-12°C+ by 2100) scenario using accelerated high-resolution SSP5-RCP85 data.

Develops a computational model to explore international risk of mass mortality due to food insecurity under the artificial ‘runaway global warming’ scenario.

Asserts the importance of high-resolution simulations of high-range global warming to inform mitigation, vulnerability, resilience and adaptation solutions.

Highlights the unequal distribution of potential human suffering, inequality and emissions, and the need for intervention strategies tailored to local contexts.


Climate and agriculture have played an interconnected role in the rise and fall of historical civilizations. Our modern food system, based on open-environment production and globalised supply chains, is vulnerable to a litany of abiotic and biotic stressors exacerbated by anthropogenic climate change. Despite this evidence, greenhouse gas emissions continue to rise. Current trajectories suggest global warming of 2.0–4.9°C by 2100, however, a worst-case emissions scenario with rapid combustion of all available fossil fuels could cause a rise of 12°C. Even if emissions decline, unprecedented atmospheric CO2-e concentrations risk triggering tipping points in climate system feedbacks that may see global warming exceed 8°C. Yet, such speculative ‘runaway global warming’ has received minimal attention compared to mainstream low- to mid-range scenarios. This study builds on The Limits to Growth to provide new insights into the international risk of mass mortality due to food insecurity based on a higher-resolution illustration of World3’s ‘runaway global warming’ scenario (~8-12°C+). Our simulation indicates rapid decline in food production and unequal distribution of ~6 billion deaths due to starvation by 2100. We highlight the importance of including high-resolution simulations of high-range global warming in climate change impact modelling to make well-informed decisions about climate change mitigation, resilience and adaptation.