Increased Global Tensions Jeopardize Climate Targets

The Sixth Assessment Report of the Intergovernmental Panel on Climate Change underscores the dependence on optimistic scenarios, specifically shared socioeconomic pathways (SSP) SSP1-1.9 and SSP1-2.6, to meet the 1.5°C or 2°C climate targets by the century’s end. However, these scenarios lack a quantitative evaluation of the influence of global tensions (represented as global military expenditure as a percentage of GDP) on CO₂ emissions. Our study uncovers that events like the 2001–2011 War on Terror and the 2022 Russian–Ukrainian war have resulted in a 0.04 (95% CI: 0.03–0.05) kg/USD increase in CO₂ emission intensity (CO₂ emissions per unit of GDP) for each 1% escalation in global tensions. This increase contributes to 27% of the total alteration in CO₂ emission intensity from 1995 to 2023. In scenarios of rising global tensions, where the global military expenditure ratio surpasses thresholds of 12% (for SSP1-1.9) or 24% (for SSP1-2.6), the global surface temperature increase would not revert below 1.5°C after the initial overshoot in SSP1-1.9, and the 2°C climate target would become unachievable in SSP1-2.6 by the century’s end. These insights highlight the potential of escalating global tensions to compromise climate targets, underlining the urgent need for a more peaceful international environment to effectively limit global warming to 1.5°C or 2°C.