Every time a meteorologist predicts a hurricane's intensity, a fishing fleet plans its season, a port authority routes a cargo ship around dangerous seas, or a government braces for El Niño, they are drawing on one critical resource: real-time ocean data. The Global Ocean Observing System (GOOS), a network of robotic floats, research vessels, and moored buoys spanning every ocean basin, makes that possible. It is, in every practical sense, the nervous system of modern civilisation's relationship with the sea and weather.

A new international study published in Nature Climate Change on 22 May, 2026 has confirmed what was previously only feared: it has found how quickly the GOOS can be disabled and by whom. This study quantifies, for the first time, how data losses in ocean monitoring would severely degrade the ocean heat estimates that underpin weather prediction, El Niño forecasting, and fisheries management.

Geographical distribution of ocean temperature profile data from different nations from 2005 to 2023. (Image by Cheng et al.)

Led by PhD candidate ZHU Yujing and Prof. CHENG Lijing from the Institute of Atmospheric Physics at the Chinese Academy of Sciences, the research team quantify the impacts of GOOS change on climate monitoring by using Ocean Heat content (OHC) as a key metric. OHC is not merely an abstraction for ocean scientists. It reflects the heat stored in the ocean and supports a wide range of forecasts and decisions, from tropical cyclone intensity and marine heatwaves to changes in fish habitats and climate variability.

Bearing this in mind, the team systematically simulated what happens to ocean monitoring quality when GOOS data are progressively removed. The results are unambiguous. Removing just 20% of observations immediately degrades the accuracy of annual ocean heating estimates by 33%. At 80% data loss, the global ocean warming signal becomes statistically indistinguishable from noise and the monitoring system ceases to be useful. Removing U.S. observations alone, which represent more than half of global data by volume, produces a 163% increase in monitoring error: worse than randomly losing 80% of all global data.

The reason is geography: U.S.-funded platforms span every ocean basin, plugging critical gaps that no other nation currently covers. More broadly, the study shows that the vulnerability of GOOS depends not only on how many observations are lost, but also on where those observations are located.

“The ocean observing system we have built over the past two decades is a remarkable collective scientific achievement. What our results add is a quantitative measure of how strongly ocean heat estimates depend on the observing system, and how quickly errors grow when observations are lost.” Prof. CHENG said.

GOOS is one of the major achievements of international scientific cooperation in ocean science. But unlike some other global systems, it is not a binding treaty. It depends on sustained contributions from many national programmes, each with different priorities, capacities and geographic footprints.

“No single nation can monitor the global ocean alone. And no nation can afford not to. The ocean does not respect borders — but the consequences of losing track of it will be felt everywhere: in food prices, in extreme weather and early warnings, in risk management and in the decisions that governments make for their economies and citizens.” Said Prof. Sabrina Speich, co-author, École Normale Supérieure – Université PSL, Paris

The results point to the importance of maintaining a sustained, coordinated and geographically balanced ocean observing system. Because different national programmes cover different ocean regions, the loss of a major contributor can create regional gaps that are difficult to compensate with observations from elsewhere.

“That is not only a climate science problem. It is a weather forecasting problem, a fisheries problem, and a national security problem.” said John P. Abraham, co-author, University of St. Thomas School of Engineering.

Paper info:

Zhu, Y., Cheng, L., Trenberth, K.E., Abraham, J.P., Speich, S., and Zhu, J. 2026: Critical dependence of global ocean heat monitoring on the ocean observing system. Nature Climate Change, https://doi.org/10.1038/s41558-026-02661-6.