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Carbon dioxide removal (CDR) is necessary for reaching net zero emissions, with studies showing potential deployment at multi-GtCO 2 scale by 2050. However, excessive reliance on future CDR entails serious risks, including delayed emissions cuts, lock-in of fossil infrastructure, and threats to sustainability from increased resource competition. This study highlights an alternative pathway─prioritizing near-term non-CDR mitigation and minimizing CDR dependence. We impose a 1 GtCO 2 limit on global novel CDR deployment by 2050, forcing aggressive early emissions reductions compared to 8-22 GtCO 2 in higher CDR scenarios. Our results reveal that this low CDR pathway significantly decreases fossil fuel use, greenhouse gas (GHG) emissions, and air pollutants compared to higher CDR pathways. Driving rapid energy transitions eases pressures on land (including food cropland), water, and fertilizer resources required for energy and negative emissions. However, these sustainability gains come with higher mitigation costs from greater near-term low/zero-carbon technology deployment for decarbonization. Overall, this work provides strong evidence for maximizing non-CDR strategies such as renewables, electrification, carbon neutral/negative fuels, and efficiency now rather than betting on uncertain future CDR scaling. Ambitious near-term mitigation in this decade is essential to prevent lock-in and offer the best chance of successful deep decarbonization. Our constrained CDR scenario offers a robust pathway to achieving net zero emissions with limited sustainability impacts.

Existing studies indicate that future global carbon dioxide (CO2) removal (CDR) efforts could largely be concentrated in Asia. However, there is limited understanding of how individual Asian countries and regions will respond to varying and uncertain scales of future CDR concerning their energy-land-water system. We address this gap by modeling various levels of CDR-reliant pathways under climate change ambitions in Asia. We find that high CDR reliance leads to residual fossil fuel and industry emissions of about 8 Gigatonnes CO2yr−1 (GtCO2yr−1) by 2050, compared to less than 1 GtCO2yr−1 under moderate-to-low CDR reliance. Moreover, expectations of multi-gigatonne CDR could delay the achievement of domestic net zero CO2 emissions for several Asian countries and regions, and lead to higher land allocation and fertilizer demand for bioenergy crop cultivation. Here, we show that Asian countries and regions should prioritize emission reduction strategies while capitalizing on the advantages of carbon removal when it is most viable. Global future carbon removal efforts could largely be concentrated in Asia. Here, this study shows that multi-gigatonnes expectation of carbon removal could have adverse impact on the energy-land-water system of countries and regions within the continent. [ABSTRACT FROM AUTHOR]

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The decarbonization of hard-to-abate transport sectors presents a significant barrier to climate mitigation necessitating the deployment of hydrogen and carbon dioxide removal (CDR) methods. Existing studies are yet to look at the combined implications of these two carbon mitigation solutions on global climate-energy-land-water system. Using an integrated assessment model, several hydrogen transition scenarios for hard-to-abate transport sectors have been developed in the current study against a pathway with just fossil and biofuels. All pathways have been modelled to achieve below 1.5 and 2 °C global mean temperature by 2100. Results show that the transition of hard-to-abate transport sectors to hydrogen would lead to reduction in emissions from the transport sector but resulting emissions from other sectors such as buildings, industry, and power would increase compared to a pathway with just fossil and biofuels. Considering the amount of energy required to transition the hard-to-abate transport sectors to hydrogen, the transition would cause an increase in land use for cultivating energy crops while reducing land allocated for food crops and pastures. Water and fertilizer demand for hydrogen production and energy crop cultivation is another issue to expect from the transition. Transitioning the hard-to-abate transport sectors to hydrogen under limited reliance on CDRs (1.8–2 GtCO 2 yr−1 until mid-century) could lead to a reduction in primary energy consumption, CO 2 emissions, CDR deployment, land expansion for bioenergy crops, water (for bioenergy crops, CDR, and hydrogen production), and fertilizer consumption by 3%, 13%, 14%, 22%, 23%, and 2%, respectively compared to a transition under an unlimited availability of CDRs. [Display omitted] • On average, hydrogen pathways reduce transport emissions by 1.1 GtCO 2 yr−1. • On average, hydrogen pathways increase total emissions by 0.7 GtCO 2 eyr−1. • Hydrogen transition expands land for bioenergy crops; reduces food crops' land. • High water use for energy crops, fertilizer & hydrogen production during transition. • Limited negative emissions in the near term could save CO 2 emissions by 13%yr−1. [ABSTRACT FROM AUTHOR]