While corals can’t speak, they etch these stories, layer by layer on their surface just as trees form rings as they grow. Now, scientists have found a way to unscramble them.

Each layer, as it turns out, captures details about the ocean at a particular time, such as temperature, salt levels, and even sea level.

By analysing coral samples from the Maldives in the central Indian Ocean, Professor Paul Kench from the Department of Geography, at the National University of Singapore’s (NUS) Faculty of Arts and Social Sciences and his collaborators from NUS and Nanyang Technological University (NTU) have reconstructed a century-long chronology of sea-level changes and climate shifts with remarkable precision.

"We hope this work contributes meaningfully to the global dialogue on resilience and preparedness."

Paul Kench

They were able to extend the sea-level record for the Indian Ocean back a further 60 years, all the way to the early 1900s, offering a much longer and clearer historical context for interpreting modern sea-level changes.

“What we’re seeing is a clear fingerprint of human-driven climate change etched into the skeletons of corals. The early acceleration in sea-level rise is a warning sign that the ocean has been responding to global warming far earlier and more strongly than we thought,” said Kench, referring to the team’s findings, which were published in Nature Communications.

To ensure that the analysed data from the coral samples were reliable, the team also compared it with real sea-level measurements from tide stations and satellites and found that they matched up closely.

The successful calibration of coral proxies against instrumental sea-level records validates that coral growth rates are reliable indicators of relative sea-level changes, making them a powerful tool for climate research.

In addition to tracking long-term sea-level changes, the coral records also captured signs of extreme climate events such as unusual warming and cooling periods, as well as droughts. These signals closely match historical weather records, offering valuable insight into the frequency and severity of past climate extremes.

Kench added: “These findings have far-reaching implications for climate adaptation planning globally, especially for low-lying and densely populated coastal regions. We hope this work contributes meaningfully to the global dialogue on resilience and preparedness.”

This pioneering research also deepens our understanding of how oceans respond to climate change, while setting a new standard for using natural archives to reconstruct environmental history.

As coastal nations around the world confront the realities of rising seas, the insights uncovered offer both a clearer view of the past and a critical guide for planning a more resilient future.

Adapted by Chua Li Min from NUS News: Natural archives in coral skeletons show sea-level rise began accelerating earlier than previously thought: NUS-led study