The Multi‐Decadal Response to Net Zero CO <sub>2</sub> Emissions and Implications for Emissions Policy
Stuart Jenkins, Benjamin M. Sanderson, Glen P. Peters, Thomas L. Frölicher, Pierre Friedlingstein, Myles Allen
Abstract
Abstract How confident are we that CO 2 emissions must reach net zero or below to halt CO 2 ‐induced warming? The IPCC's sixth assessment report concluded that “limiting human‐induced global warming to a specific level requires … reaching at least net zero CO 2 emissions.” This is much stronger language than the special report on the global warming of 1.5°C, which concluded that reaching net zero CO 2 emissions would be sufficient. Here we show that “approximately net zero” is better supported than “at least net zero.” We estimate the rate of adjustment to zero emissions (RAZE) parameter (−0.24 to +0.17%/yr), defined as the fractional change in CO 2 ‐induced warming after CO 2 emissions cease. The RAZE determines the CO 2 emissions compatible with halting warming over multiple decades: in 1.5°C‐consistent scenarios, CO 2 emissions consistent with halting anthropogenic warming are +2.2 GtCO 2 /yr (5–95th percentile range spans −7.3 to +6.2 GtCO 2 /yr), similar to the expected emissions from unmodelled Earth system feedbacks.