Increased Global Tensions Jeopardize Climate Targets

The Sixth Assessment Report of the Intergovernmental Panel on Climate Change highlights the reliance on optimistic scenarios such as shared socioeconomic pathways SSP1-1.9 and SSP1-2.6 to achieve the 1.5°C or 2°C climate targets by the end of this century [1] . However, these scenarios have not quantitatively assessed the impact of global tensions (measured as global military expenditure as a percentage of GDP) on CO 2 emissions. Our research reveals that events such as the 2001–2011 War on Terror and the 2021 prelude to the Russian–Ukrainian war have led to a 0.041% (95% CI: 0.030–0.052) kg/USD increase in CO 2 emission intensity (CO 2 emissions per unit of GDP) for each 1% rise in global tensions. This increment accounts for 30% of the total change in CO 2 emission intensity from 1995 to 2021. In the case of escalating global tensions, with the global military expenditure ratio exceeding thresholds of 11% (for SSP1-1.9) or 23% (for SSP1-2.6), the global surface temperature increase would fail to return below 1.5°C after the initial overshoot in SSP1-1.9, and the 2°C climate target would become unattainable in SSP1-2.6 by the end of this century. These findings underscore the potential of escalating global tensions to undermine climate targets, emphasizing the critical need for a more peaceful international environment to effectively limit global warming to 1.5°C or 2°C.