The primary factors influencing the cooling effect of carbon dioxide removal

Abstract

Carbon dioxide removal (CDR) is a crucial approach in achieving the goals set by the Paris Climate Agreement. However, understanding the cooling effect (CE) of CDR and its primary controlling factors has been challenging due to the limited number of models conducting the CDR simulation. To address this, we employed an energy balance model (EBM), which effectively captures or reproduces the global mean surface air temperature change to CO2 forcing. The outputs of the EBM revealed that even with the same CDR rate, the CE diverse significantly (σ=0.7 K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma =0.7{K}$$\\end{document}). Two main factors significantly affect the CE of CDR. The primary factor is the coefficient of the vertical heat exchange in the ocean [contributes to σCE=0.7 K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma \\left({CE}\\right)=0.7{K}$$\\end{document}], which governs the heat uptake and release of the deep ocean. It directly impacts the heat absorbed by the Earth’s surface and influences the magnitudes of the transient climate responses. The second factor is the estimation of effective radiative forcing (ERF) resulting from changes in CO2 concentration [contributes to σCE=0.6 K\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sigma \\left({CE}\\right)=0.6{K}$$\\end{document}]. This estimation is directly associated with the amplitude of the CO2 radiative forcing and the responses of relevant energy processes, thereby influencing the temperature change. Regarding the timing of the CE emergence, the influences of processes within the EBM are quite small. Therefore, an accurate estimation of the vertical heat exchange in the ocean and ERF may favor designation of a better pathway to achieve the temperature goals outlined in the Paris Climate Agreement.