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Abstract

Achieving the Paris Agreement’s long-term temperature goal of limiting global warming well below 2°C while pursuing efforts to limit it to 1.5°C requires rapid and sustained reductions in greenhouse gas (GHG) emissions and CO2 to be withdrawn from the atmosphere and safely stored. However, pathways consistent with the Paris long-term temperature goal span a wide range of emission reductions in coming years: the IPCC indicates 34–60% cuts in GHG emissions between 2019 and 2030. This range is a major source of policy uncertainty. A key determinant of the rate at which emissions must be reduced this decade is the extent to which CO2 removal (CDR) is relied on later to withdraw emissions from the atmosphere. Here, we evaluate the dependence on CDR of 71 states, primarily in their near and long-term climate strategies submitted to the UNFCCC by May 2024, and the associated risks. Our analysis finds substantial ambiguities in how states plan to meet their climate targets. A feature of this ambiguity is that states expect to rely heavily on novel and conventional CDR options to meet their climate goals, and in some cases, rely on removals delivered in other states’ territories. Pathways that overshoot 1.5°C and use CDR to remove emissions produced in excess of the 1.5°C-aligned carbon budget will result in more severe climate change impacts and higher risks of crossing planetary tipping points. Moreover, states’ disclosed reliance on CDR is highly exposed to risks to its delivery, and non-delivery of planned CDR would raise global temperatures further, worsening impacts of climate change. Our findings provide a basis for enhanced scrutiny of states’ targets. The risks associated with heavy reliance on CDR to meet climate goals indicate that states should prioritize pathways that minimize overshoot and the reliance on CDR to reach net-zero CO2 emissions.