Overview of Climate Intervention Strategies on Carbon Dioxide Removal and Reliable Sequestration

Today, the burning of fossil fuels, including coal, oil, and gas meets more than 85% of the world's commercial energy needs. Our planet has entered a period of changing climate never before experienced in recorded human history, primarily caused by the rapid build-up of carbon dioxide (CO₂) in the atmosphere from fossil fuel burning. The scientific community agrees that there are a number of risks associated with climate change, including sea level rise, drought, heat waves, more severe storms, increasing precipitation intensity, and ocean acidification. Natural processes will eventually return Earth to pre-industrial CO₂ levels once emissions cease; however, those processes operate on millennial time scales or longer. Therefore, the climate changes and impacts from elevated CO₂ levels will persist for millennia if humans fail to intervene. Reducing CO₂ emissions to the atmosphere will require a portfolio of solutions, some of which include CO₂ capture and storage (CCS), biomass-sourced energy (e.g., bioenergy), increased dependence on renewables, reduction in deforestation, and efficiency increases. And although there are ongoing efforts on climate adaptation in many communities, both humans and ecosystems face substantial challenges in adapting to the varied impacts of climate change over the coming century. For that reason, it is crucial to examine other strategies for limiting the risks from climate change, even as mitigation and adaptation remain the primary emphasis. Also, if society continues its trajectory on increased fossil fuel dependence in the coming decades, mitigation or avoidance of CO₂ emissions will no longer be the primary solution for reducing the risks associated with climate change; rather, the removal of CO₂ from the atmosphere (CDR) will be required. Strategies for CDR may include linking bioenergy with CCS, direct air capture, land management, and accelerated weathering. These topics will be discussed, in particular, in terms of their impact and related potential for significantly reducing atmospheric CO₂ on a time scale of interest.