Net-zero approaches must consider Earth system impacts to achieve climate goals

Commitments to net-zero carbon dioxide (CO 2 ) or greenhouse gas (GHG) emissions targets now cover 88% of countries’ emissions. Underlying the accounting behind net-zero frameworks is the assumption that emissions can be balanced with removals such that their net climate effect is zero. However, when considering the full climate impacts of CO 2 emissions and removals, there are reasons to expect that the two are not equivalent in terms of their climate outcomes. We identify potential contributors to non-equivalence, including impermanence, biogeophysical and non-CO 2 GHG effects, and argue that these non-equivalencies need to be accounted for to achieve climate goals. Given key uncertainties about the full climate impact of CO 2 removal, it is prudent to prioritize emission reductions over removals. Underlying net-zero GHG accounting approaches is the assumption that emissions can be balanced by removals such that their net climate effect is zero. However, CO 2 removals may not be equal and opposite to CO 2 emissions in their climate impact, indicating the need to consider non-CO 2 effects.