WORLD NEWS
Centuries after net-zero GHG, a study finds at least 0.6 C of cooling
Sustaining net-zero across multiple greenhouse gases could lower global mean temperature by at least 0.6 C over the following centuries, according to a new analysis.
That does not mean stopping every emission today would cool Earth immediately. The result depends on continued net-negative CO2 removing enough carbon to offset residual methane, nitrous oxide, and other gases.
CO2 cessation is not net-zero GHG
The long-term temperature response after CO2 emissions stop is called the zero emissions commitment, or ZEC. Using three constrained climate metrics, the study estimated a near-zero multi-century ZEC for historical CO2 emissions.
Real net-zero GHG policy is different. Residual methane and nitrous oxide are balanced with CO2 removal, so CO2 itself can remain net-negative even when the aggregate is zero.
Why at least 0.6 C of cooling appears
The authors call the policy-relevant effect Net-ZEC. Across scenarios and greenhouse-gas offsetting conventions, it produced at least 0.6 C of multi-century cooling after net-zero GHG.
The driver is continued net CO2 removal used to offset residual non-CO2 gases. Net-zero is therefore a state that must be maintained, not a date that ends the work.
How this changes the simple picture
The physical statement that temperature roughly stabilizes after CO2 cessation is not the same as sustaining net-zero across a mixture of gases. The IPCC also says sustained net-zero GHG is projected to bring a gradual decline after peak temperature and implies net-negative CO2.
The new study separates and quantifies these two ideas.
Do not read 0.6 C as a short-term forecast
The result unfolds over centuries and depends on simplified climate models, existing multi-model data, policy scenarios, greenhouse-gas metrics, and sustained removal. It does not mean heatwaves or extreme rainfall disappear quickly.
Sea level, ocean heat, and ice sheets also do not reverse at the same rate as surface temperature.
The policy has to persist
Cooling occurs only if net-zero GHG and net-negative CO2 removal are maintained for the long term. A change in residual emissions or removal changes the path. More complex Earth-system model tests are the next important check.
Official Primary Sources
Nature Climate Change original study