We would like to inform you that the Tropical Pacific Observing System 2020 (TPOS 2020) Project released its Second Report draft for community review. TPOS 2020 released its First Report in 2016 and the Second Report builds on that document. It updates the evolving design of the Backbone observing system, drawing on new research and evidence including feedback received on the First Report, and responds to gaps identified by sponsors of the Project. If you would like to be a reviewer of the Second Report, please find it on the TPOS 2020 website (http://tpos2020.org/project-reports/second-report/), along with the Review Template. The marine biogeochemistry community might be particularly interested to review the contents of Chapter 4: Biogeochemical and Ecosystem Observations.