Radio has recorded the highest ratio of advertising attention to carbon emissions in a study aiming to encourage advertisers to consider environmental impact alongside campaign effectiveness.
The study, A Metric for Effective & Responsible Advertising was conducted by Ebiquity, Net Zero Media and Lumen. It introduces the attention-to-emissions (A/E) ratio — a metric that compares the attention seconds generated per £1 of media spend with the estimated grams of carbon dioxide-equivalent (gCO2e) emissions generated per £1 spent.
A higher ratio indicates a channel generates more attention relative to its estimated emissions, providing advertisers with an additional measure for comparing media investments.
The research analysed campaigns from 10 UK advertisers during 2024 and 2025, covering TV, VOD, digital, OOH, print and radio.
Radio recorded the highest A/E ratio, driven by the significantly higher attention seconds it generated per £1 spent compared with the other channels analysed.
The study also found that the six advertisers with the highest A/E ratios all included radio in their media plans. None of the four lowest-ranked advertisers did.
TV recorded the second-highest A/E ratio, producing the lowest estimated emissions per £1 spent.
Print had the lowest A/E ratio, with estimated emissions per £1 spent 2.45 times the study average. However, magazines outperformed newspapers, with the cost-efficiency of generating attention seconds a substantial contributor to the difference.
That said, the researchers warned that the print sample was limited to five advertisers and should not be considered representative of the wider market.
Direct buying implications
Digital recorded the second-lowest A/E ratio of the channels analysed. However, when breaking down the category into display, video and audio, the findings showed that digital audio had a significantly higher ratio than the others.
The report also examined the difference between buying methods. Direct buying recorded the highest A/E ratio, followed by preferred/guaranteed and open marketplace.
Direct buying generated the lowest estimated emissions per £1 spent but was also the least cost-efficient at generating attention. Open marketplace showed the reverse, producing the highest attention seconds per £1 alongside the highest estimated emissions.
Mike Follett, CEO and co-founder of Lumen, said the differences in buying methods could be linked to the energy requirements of programmatic advertising, including the data centres used to support audience targeting.
Sustainable media choices need to make commercial sense
Paul Elliott, group director of strategic operations at Ebiquity, told The Media Leader that the findings should not be interpreted as a ranking of which channels to favour.
Instead, he explained, the research aims to encourage advertisers to examine the relationship between attention and emissions when reviewing media plans.
“Where is attention being generated? What emissions are associated with that investment? And what explains the differences? These are questions worth exploring with agencies and media partners when reviewing media plans, from overall channel allocation through to individual placement choices,” Elliott said.
“We hope the research encourages exactly that kind of conversation.”
The report cited 2024 research by the IPA Media Climate Action Group and Ipsos that found 48% of the ad industry believe it has a negative impact on climate change, while 70% of ad agency employees said the industry was doing too little.
Furthermore, the researchers noted that there is growing pressure within the industry for lower-carbon media choices to make commercial sense. The A/E ratio was developed to bring environmental impact and attention into the same analysis.
Follett described the metric as a way for advertisers to quantify how their media mix could maximise returns while minimising environmental impact.
He added that the research showed “you can achieve your commercial objectives without it costing the Earth”.
The research emphasised that the findings are directional rather than prescriptive buying advice. The A/E ratio should be used as an additional measure for media planning and post-campaign evaluation, alongside established measures such as reach, brand and sales performance.
Follett said the next step in the research would be to further validate the correlation between attention and business outcomes in the context of the A/E ratio.
