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Section 2
Section 1
Section 2
Cross-Section Box.1: Understanding Net Zero CO2 and Net Zero GHG Emissions 
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 in other GHG emissions (see 3.3.2). Future additional warming will depend on future emissions, 
with total warming dominated by past and future cumulative CO2 emissions. {WGI SPM D.1.1, WGI Figure SPM.4; SR1.5 SPM A.2.2} 
Reaching net zero CO2 emissions is different from reaching net zero GHG emissions. The timing of net zero for a basket of GHGs depends 
on the emissions metric, such as global warming potential over a 100-year period, chosen to convert non-CO2 emissions into CO2-equivalent (high 
conﬁdence). However, for a given emissions pathway, the physical climate response is independent of the metric chosen (high conﬁdence). 
{WGI SPM D.1.8; WGIII Box TS.6, WGIII Cross-Chapter Box 2}
Achieving global net zero GHG emissions requires all remaining CO2 and metric-weighted98 non-CO2 GHG emissions to be 
counterbalanced by durably stored CO2 removals (high conﬁdence). Some non-CO2 emissions, such as CH4 and N2O from agriculture, 
cannot be fully eliminated using existing and anticipated technical measures. {WGIII SPM C.2.4, WGIII SPM C.11.4, WGIII Cross-Chapter Box 3}
Global net zero CO2 or GHG emissions can be achieved even if some sectors and regions are net emitters, provided that 
others reach net negative emissions (see Figure 4.1). The potential and cost of achieving net zero or even net negative emissions 
vary by sector and region.