The electrification of everything.

Energy - in one form or another - is by far the largest source of GHG emissions. The decarbonisation pathway is unusually clear:

1. (1) Decarbonise the grid - every sector that runs on electricity improves simultaneously, without waiting for behaviour change.
2. (2) Electrify end uses - buildings, transport and industry switching from direct fossil fuel combustion to electricity, locking in those grid gains permanently.

To make progress visible, emissions are attributed to whoever consumes the energy, not to the power station that generates it. Under this view, each sector owns its full footprint — including the electricity it draws from the grid — so reductions show up where the decisions are actually made.

What remains after both steps is a residual ~12% with no clean end-use owner: fugitive methane from pipelines, gas flared at wellheads, refineries burning fuel to process fuel. This is the hard tail — the portion that neither a cleaner grid nor a more electric economy will reach on its own.