Big brands have moved well beyond criticisms of greenwashing, and even simple "carbon offsets" to actually reduce the amount of carbon emitted by advertising and media.

"You can't just create your own metric and call it certified. Or anoint vendors to be the best vendors on the planet when there's no basis for that," Ivie says about industry players going rogue.

"One of the things we thought was really important to call out was the blurriness of media and how everything is evolving in a way that makes the individual line items increasingly less relevant," GroupM's Wieser explains.

The agency's new audience measurement framework will transact all 2022-23 deals based on Nielsen's current data, but will shadow them with alternative audience and outcome-based measurement to see what works best