Over the last few years, the in situ observing system, made up of many thousands of ocean observing platforms, has developed significantly with emerging networks, advances in new technologies, and improved capabilities. This system supplies scientists and marine and weather forecasters with essential global, multidisciplinary, high-quality data, crucial to support safety of life and property at sea, maritime commerce, and the well-being of coastal communities. It also provides observations to monitor the impacts of long-term climate change and information on the increasing stress on the ocean from human activities.

To continue to evolve this system towards an integrated, fit-for-purpose and sustained global network, the Ocean Observing System Report Card 2021 provides insight into the status of the global ocean observing system, assessing networks’ progress, focusing on the challenges needed to keep improving this system, and encouraging collaborations and new partners to join the ocean observing community.