Net zero greenhouse gases
A balance between human-caused greenhouse gas emissions and removals, weighted using a specified metric.
Example
The gases included and the metric chosen determine the balance.
The catch
Net zero GHG and net zero CO₂ do not have identical temperature implications.
In more depth
Net zero greenhouse gases, explained.
Reaching net zero greenhouse gases usually means going net negative on CO₂, because some agricultural methane and nitrous oxide are hard to eliminate and must be balanced by extra removals. That makes it a more demanding goal than a CO₂-only target with the same date.
IPCC AR6 finds that reaching and sustaining global net zero greenhouse gases, weighted with GWP100, would see temperatures peak and then slowly decline. Part of the reason lies in the metric, which treats steady emissions of a short-lived gas as if they kept adding warming. Some researchers propose alternative metrics for short-lived gases, which would change what a farm or a country must do to claim balance. The gas list and the metric usually sit in the small print of such targets, and both repay a close read.