Brian O'Kelley is often considering the godfather of ad tech, having invented programmatic advertising when he built AppNexus. Now he's launched a new company called Scope3 to fix the environmental damage done by modern ad tech.
Brian talks to Sean Aylmer about what he would have done differently if he had his time again.

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Q+A: After all the hype, green investing is 'growing up, not winding down'
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