GWP100
Global warming potential evaluated over one hundred years after a pulse emission.
Example
Many greenhouse gas inventories use this horizon for reporting.
The catch
It is an accounting choice, not the date when a gas stops affecting climate.
Related terms
Global warming, Global warming potential, Greenhouse gas, Reporting, Absolute emissions, Activity data
In more depth
GWP100, explained.
GWP100 is the convention that lets climate reports add different gases into one total, and its main virtue is consistency. National inventories under the Paris Agreement and corporate reports under the GHG Protocol both use it, which lets a tonne of CO₂e from one country or company be compared with another. On this horizon, methane warms about 30 times as much as CO₂, mass for mass (IPCC AR6, UNEP).
Nothing in the physics singles out 100 years. The horizon spread through early climate treaties and stays largely for consistency with earlier inventories. Its weakness shows with short-lived gases. Methane does most of its warming in the first decades after release, so averaging over a century dilutes that early effect, and methane studies often report GWP20 alongside it.