Stakeholders increasingly expect businesses to account for the environmental externalities of their decisions, as evidenced by the rise of environmental, social and corporate governance (ESG) investing and employee activism around climate change. Migrating to the cloud offers the potential for more efficient energy usage — the cloud providers have much more scale to justify investment in green energy sources and R&D — but the downside of software abstractions for cloud users is that those abstractions also hide the energy impact as the actual data centers are hidden from view and financed by another company. Cloud Carbon Footprint, a new open-source tool, takes advantage of cloud APIs to provide visualizations of estimated carbon emissions based on usage across AWS, GCP and Azure. It uses heuristics like Etsy's Cloud Jewels to estimate energy usage and public data sources to convert energy usage into emissions based on the carbon intensity of the cloud region's underlying energy grid (GCP publishes this data already). The tool's dashboards act as information radiators, allowing decision makers to modify setups to cut costs and emissions at the same time. The linkage of cloud regions to carbon intensity of the underlying grid provides a nudge to switch dirty workloads to regions with greener energy sources.