Most countries report their anthropogenic 
land CO2 ﬂuxes including ﬂuxes due to human-caused environmental change (e.g., CO2 fertilisation) on ‘managed’ land in their National GHG inventories. Using emissions 
estimates based on these inventories, the remaining carbon budgets must be correspondingly reduced. {WGIII SPM Footnote 9, WGIII TS.3, WGIII Cross-Chapter Box 6}
129 The central case RCB assumes future non-CO2 warming (the net additional contribution of aerosols and non-CO2 GHG) of around 0.1°C above 2010–2019 in line with stringent 
mitigation scenarios. If additional non-CO2 warming is higher, the RCB for limiting warming to 1.5°C with a 50% likelihood shrinks to around 300 GtCO2. If, however, additional 
non-CO2 warming is limited to only 0.05°C (via stronger reductions of CH4 and N2O through a combination of deep structural and behavioural changes, e.g., dietary changes), 
the RCB could be around 600 GtCO2 for 1.5°C warming. {WGI Table SPM.2, WGI Box TS.7; WGIII Box 3.4}
130 When adjusted for emissions since previous reports, these RCB estimates are similar to SR1.5 but larger than AR5 values due to methodological improvements. {WGI SPM D.1.3}
131 Uncertainties for total carbon budgets have not been assessed and could affect the speciﬁc calculated fractions. 
132 See footnote 131. 
133 These projected adjustments of carbon sinks to stabilisation or decline of atmospheric CO2 concentrations are accounted for in calculations of remaining carbon budgets. 
{WGI SPM footnote 32}
If the annual CO2 emissions between 2020–2030 stayed, on average, 
at the same level as 2019, the resulting cumulative emissions would 
almost exhaust the remaining carbon budget for 1.5°C (50%), and 
exhaust more than a third of the remaining carbon budget for 2°C 
(67%) (Figure 3.5).