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Long-Term Climate and Development Futures
Section 3
3.3.2 Net Zero Emissions: Timing and Implications
From a physical science perspective, limiting human-caused 
global warming to a speciﬁc level requires limiting cumulative 
CO2 emissions, reaching net zero or net negative CO2 emissions, 
along with strong reductions of other GHG emissions 
(see Cross-Section Box.1). Global modelled pathways that reach 
and sustain net zero GHG emissions are projected to result in 
a gradual decline in surface temperature (high conﬁdence). 
Reaching net zero GHG emissions primarily requires deep reductions in 
CO2, methane, and other GHG emissions, and implies net negative 
CO2 emissions.134 Carbon dioxide removal (CDR) will be necessary to 
achieve net negative CO2 emissions135. Achieving global net zero 
CO2 emissions, with remaining anthropogenic CO2 emissions balanced by 
durably stored CO2 from anthropogenic removal, is a requirement to 
stabilise CO2-induced global surface temperature increase (see 3.3.3) 
(high conﬁdence). This is different from achieving net zero GHG 
emissions, where metric-weighted anthropogenic GHG emissions (see 
Cross-Section Box.1) equal CO2 removal (high conﬁdence). Emissions 
pathways that reach and sustain net zero GHG emissions deﬁned by the 
100-year global warming potential imply net negative CO2 emissions 
and are projected to result in a gradual decline in surface temperature 
after an earlier peak (high conﬁdence). While reaching net zero CO2 or net 
zero GHG emissions requires deep and rapid reductions in gross 
emissions, the deployment of CDR to counterbalance hard-
to-abate residual emissions (e.g., some emissions from agriculture, 
aviation, shipping, and industrial processes) is unavoidable (high 
conﬁdence).