UC San Diego

Though highly motivated to slow the climate crisis, governments may struggle to impose costly polices on entrenched interest groups, resulting in a greater need for negative emissions. Here, we model wartime-like crash deployment of direct air capture (DAC) as a policy response to the climate crisis, calculating funding, net CO₂ removal, and climate impacts. An emergency DAC program, with investment of 1.2-1.9% of global GDP annually, removes 2.2-2.3 GtCO₂ yr^-1 in 2050, 13-20 GtCO₂ yr^-1 in 2075, and 570-840 GtCO₂ cumulatively over 2025-2100. Compared to a future in which policy efforts to control emissions follow current trends (SSP2-4.5), DAC substantially hastens the onset of net-zero CO₂ emissions (to 2085-2095) and peak warming (to 2090-2095); yet warming still reaches 2.4-2.5 °C in 2100. Such massive CO₂ removals hinge on near-term investment to boost the future capacity for upscaling. DAC is most cost-effective when using electricity sources already available today: hydropower and natural gas with renewables; fully renewable systems are more expensive because their low load factors do not allow efficient amortization of capital-intensive DAC plants.