[indigo945]

I see big privacy concerns with this, because most likely the only practical way to make this work is to log every purchase any citizen does and store it for several years. It would also be very unlikely to incentivise those people who don't already care about climate change, and might actually serve to disincentivise them because being more wasteful makes them look better among their peers. For a case study on this, consider the Rolling Coal movement.

[edejong]

Supermarkets already do this. They store it for much longer than several years.