Scenarios
Illustrative IPCC AR6 pathways (CMIP6 / ScenarioMIP). SSP5-8.5 remains a high bound, rarely considered the most likely trajectory today.
The two-reservoir model does not explicitly simulate the carbon cycle. Forcing is prescribed and calibrated to the ZECMIP median at 50 years; other forcing agents, including aerosols, are not represented.
Projections · ZEC - anthropogenic CO₂ set to zero in 2025
“Anthropogenic CO₂ set to zero in 2025” animation
Automatically advances the slider on the teaching ZEC experiment: anthropogenic CO₂ emissions set to zero in 2025, followed by prescribed forcing; +50-year milestone or trajectory to 2150.
EEI and OHC: 2-reservoir model orders of magnitude; only temperature is calibrated to AR6. After 2025: EEI and OHC from the model (inertia), not IAP/CAS observations.
- ZEC - anthropogenic CO₂ set to zero in 2025
- ZECMIP · 18 models (9 ESM + 9 EMIC) (P10–P90)
- ZECMIP median
Compare as overlay (max 3 SSP scenarios)
ZEC · warming after stop
Zero Emissions Commitment measures the temperature change after anthropogenic CO₂ emissions cease. This two-reservoir model is compared with the ZECMIP synthesis / AR6:
The 2-reservoir model (−0.05 °C at 50 yr) sits within the ZECMIP envelope (P10–P90), close to the median (−0.05 °C).
ZECMIP source: MacDougall et al. 2020, Biogeosciences, doi:10.5194/bg-17-2987-2020 — 1000 PgC emitted, then zero CO₂ emissions (atmospheric CO₂ evolving freely)
Inertia · surface vs deep ocean
In 2025, at the start of the experiment with anthropogenic CO₂ emissions set to zero, the surface is 1.39 °C above 1850-1900 and the deep ocean is 0.08 °C. In this model, the 1.31 °C gap takes several centuries to close.
Model ZEC: −0.03 °C at 25 yr, −0.05 °C at 50 yr. ZECMIP median at 50 yr: −0.05 °C. EEI takes ~62 years to halve (≈ 2087).
Anthropogenic CO₂ at zero (ZEC)
In this educational experiment, anthropogenic CO₂ emissions are set to zero in 2025. CO₂ already in the atmosphere may continue to be absorbed by natural sinks. The two-reservoir model does not explicitly simulate the carbon cycle: it prescribes a forcing decline calibrated to the ZECMIP median at 50 years. It does not represent other forcing agents, including the climate effect of a rapid decline in aerosols.
Zero Emissions Commitment (ZEC) is additional warming in the following decades — close to zero according to AR6: below 0.3 °C in absolute value at 50 years, of uncertain sign (ZECMIP median −0.05 °C). The model's deep ocean (a model variable, not Argo data) takes centuries to catch up with the surface: that is the inertia this lab visualises.
AR6 indicates that a deep, rapid emissions cut discernably slows warming in about two decades — but this simplified experiment does not erase inertia already accumulated.