You also say that top-down hasn't been working very well and so we may be running out of time. Isn't that a strong signal that we should look at a different approach?
As technologists, we can plainly see the power of our mobile computers and the influence they have over our behavior. Advertising is huge because it works. But what if its influence drives us to disproportionately purchase products or services that contribute to climate change?
If advertisement works, and technology works, and people's behavior is already being directed, then why can't we direct it another way?