As brands, publishers, agencies and programmatic adtech firms work to make media plans that emit less carbon, new challenges emerge, from publishers needing more data to make their sites cleaner, to low adoption from the buy side.

Current challenges were a key theme at the Green Media Summit in New York last week, where around 400 people gathered at the Javits Center to discuss how marketers can contribute to slowing climate change. The crowd grew by over 100 from last year, when the focus was more on education than implementation.

Here are three roadblocks the marketing industry faces:

Publishers need more data

Adtech solutions to help brands buy more efficiently focus on buying publishers with lower carbon footprints. However, the data publishers need to determine which parts of their sites emit the most carbon and are housed within third parties, which publishers don’t have access to.

“We are missing so much data in the ecosystem, [so] we don’t know how to pull back,” said Bridget Williams, chief commercial officer and senior vice president of digital publishing at Hearst.

If publishers had more information from adtech partners on whether a particular impression was attractive to the buy side, they could build a more efficient programmatic tech stack where they only work with partners guaranteed to deliver results, said Stephanie Layser, worldwide head of publisher adtech at Amazon Web Services.

This data often comes in the form of log files, Layser added. Publishers have long been frustrated that Google’s demand-side platform (DSP) Demand & Video 360 does not give them access to log data at the impression level.

Publishers’ frustrations about adtech firms blocking ad revenue for reasons unknown to the publishers themselves are not isolated to sustainability: Verification firms flag sites as made-for-advertising (MFA) without giving publishers visibility into their methodology.

Going green doesn’t earn green

Theoretically, if more buyers prioritize buying sustainable media, publishers with greener sites should see a lift in revenue.

Currently, there’s been no benefit to the bottom line, said Julia Li, director of social impact, sustainability at publishing network Mediavine.