New research led by Rutgers University scientists warns that Earth’s seas are now rising faster than at any time in the last four millennia. The study, published in Nature, finds that sea levels have climbed an average of 1.5 millimeters per year since 1900 — outpacing every century-long period over the past 4,000 years.
China’s rapidly sinking coastal regions, including Shanghai, Shenzhen, and Hong Kong, face some of the world’s most severe threats, the research shows. These areas are vulnerable not only to higher oceans driven by climate change but also to subsidence, or the gradual sinking of land caused by natural processes and human activity.
Groundbreaking Geological Analysis of 12,000 Years of Change
To uncover the historical context of modern sea rise, researchers reconstructed water levels spanning nearly 12,000 years, tracing from the end of the last ice age to the present-day Holocene epoch.
The team analyzed thousands of geological records from ancient coral reefs and mangrove deposits, which preserved detailed evidence of long-term sea-level fluctuations.
“The global mean sea level rise rate since 1900 is the fastest rate over the last 4,000 years,” said Dr. Yucheng Lin, the study’s lead author and research scientist at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Hobart, Australia. Lin completed the research as a postdoctoral associate at Rutgers University.
What’s Driving the Rapid Rise
According to the study, two forces are primarily responsible for accelerating sea-level increases: thermal expansion and melting glaciers and ice sheets. As Earth’s climate warms, ocean water expands as it absorbs heat — a process called thermal expansion — while melting ice from Greenland and Antarctica adds vast freshwater volumes to global oceans.
“Getting warmer makes your ocean take up more volume,” Lin explained. “And glaciers respond faster because they’re smaller and more sensitive to temperature shifts than continental ice sheets. We’re seeing growing acceleration, especially from Greenland.”
These twin mechanisms are expected to drive sea levels up by tens of centimeters this century, and by several meters over coming centuries if global emissions remain unchecked.
China: The Epicenter of Coastal Risk
While rising seas are a global crisis, the study highlights that China faces a double threat — rising oceans compounded by ground subsidence.
Many of China’s largest cities, including Shanghai, Shenzhen, and Hong Kong, are built on soft deltaic plains formed by river sediment. Such regions naturally sink over time. However, extensive groundwater extraction and construction load have dramatically accelerated this rate.
In Shanghai alone, areas of the city sank more than one meter during the 20th century, vastly exceeding the global average sea-level rise over the same period.
“We quantified the natural rate of sea-level rise for this region,” Lin explained. “But groundwater extraction makes the land sink much faster than nature would allow.”
Delta Regions Under Dual Pressure
The research focused on two of China’s most economically important — and vulnerable — regions: the Yangtze River Delta and the Pearl River Delta. Together, these areas are home to hundreds of millions of people and serve as critical industrial and trade centers for the global economy.
Delta lands are naturally flat and fertile, encouraging population growth and development. However, these same characteristics make them highly susceptible to flooding.
Even small increases in sea level, Lin noted, greatly magnify flood risk in these low-elevation areas. “Centimeters of rise can reshape entire delta landscapes,” he said.
Global Implications: The Supply Chain at Risk
Coastal infrastructure is vital to the functioning of the global economy, serving as hubs for shipping, food transport, and energy distribution.
“Even those living far inland rely on goods, fuel, and food that move through ports exposed to sea-level rise,” said Professor Robert Kopp, study co-author and Distinguished Professor of Earth and Planetary Sciences at Rutgers.
Disruption at major coastal ports — from Hong Kong to Jakarta to New York — could cascade through trade networks, potentially upending international supply chains and food security systems.
Mapping the 21st Century’s Coastal Crisis
The team combined geological data with modern satellite measurements of land sinking, creating detailed vulnerability maps of China’s coastal zones. These maps reveal overlapping factors that amplify local risks — from subsiding terrain to dense urban populations concentrated in flood-prone zones.
Such maps are valuable for city planners and policymakers, offering evidence-based guidance for climate adaptation, flood defenses, and coastal relocation strategies. “Shanghai now isn’t sinking as fast,” Lin noted, crediting the city’s government for limiting groundwater extraction and reinjecting freshwater into aquifers. “They recognized the problem early and acted to slow it. That’s a model for others to follow.”
A Century of Acceleration, A Future of Uncertainty
The Rutgers study documented an unmistakable acceleration in sea-level rise since the dawn of the Industrial Age. Global mean sea levels, stable for thousands of years prior to 1900, began rising sharply as carbon dioxide emissions escalated.
From 1900 to 2000, average seas rose by 1.5 millimeters per year; since 1993, satellite data show that rate has more than doubled to 4.5 millimeters per year.
If current trends continue, scientists project oceans could rise by at least half a meter by 2100, and as much as one meter or more under high-emission scenarios. Longer term, multi-meter increases are virtually locked in, given ongoing ice losses and ocean warming.
Preparing for Rising Waters
Despite sobering results, the research offers hope: human intervention and adaptive design can curb localized risks. Shanghai’s subsidence control, for example, shows how engineering and policy can slow or reverse land sinking.
Cities across the world — from Jakarta to Dhaka and Lagos to New Orleans — can apply similar measures, including restricting groundwater extraction, constructing flood-resistant infrastructure, and incorporating sea rise projections into urban planning.
“Sea-level rise is slow but unstoppable in the short term,” said geophysicist Natalya Gomez, co-author of the study. “The sooner we plan, the better our chances of maintaining resilient coastlines and protecting lives and livelihoods.”
Lessons for the Planet
Although China serves as a focal case, the findings have far-reaching global relevance. About 750 million people live within five kilometers of coastlines worldwide, and many major cities — from New York to Manila — are built on similar sinking plains.
“Deltas are where civilizations thrive — fertile, productive, and accessible,” Lin reflected. “But they’re also exceptionally fragile when human activity and climate change combine. Sustained sea-level rise could submerge them far faster than expected.”
