Sea level is rising as it hasn't in 4,000 years, and scientists warn that China's giant cities may face a much bigger problem than it seemed.

Sea level is rising as it hasn’t in 4,000 years, and scientists warn that China’s giant cities may face a much bigger problem than it seemed.

Written by Fabio Lucas Carvalho

Published on 26/04/2026 at 00:42

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Rutgers University study indicates that sea level is advancing at the fastest pace in at least 4,000 years, while land subsidence amplifies the risk in China’s coastal megacities, especially in deltas characterized by low altitude, intense urbanization, and industrial activity

Sea level is rising at an unparalleled pace for at least 4,000 years, while major coastal centers in China face an additional risk: gradual land subsidence. The combination of rising waters and subsidence places cities located in river deltas among the areas most vulnerable to increasingly frequent floods.

Rutgers University researchers point out that the ocean’s advance occurs simultaneously with parts of urban land losing altitude, especially in regions marked by intense human activity. The analysis indicates that this process can accelerate impacts in coastal centers and also shows that part of the problem can be reduced with urban management measures.

Sea level rises at a record pace for over a century

The study estimates that, since 1900, the global average sea level has risen by about one and a half millimeters per year. This pace is described by researchers as faster than any century-long period identified in geological evidence from the last four millennia.

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How researchers reconstructed the ocean’s history

To understand sea level variation before modern instrumental records, the team used thousands of natural markers. These include ancient coral reefs and mangroves, environments capable of preserving signs of where the coastline was at different periods.

These clues allowed scientists to track changes that occurred throughout the Holocene, the current period of Earth’s history that began after the last major glacial era. The reconstruction helped compare the ocean’s recent behavior with trends observed over a scale of thousands of years.

The analysis also combined these natural records with modern measurements, such as tide gauges installed on the coast. These instruments act as long-term rulers and help measure water variation over time.

The researchers also used a statistical tool called PaleoSTeHM. This resource helped gather noisy records into a clearer reconstruction, considering margins of uncertainty and connecting ancient geological data to recent measurements.

Ocean heat and ice melt drive the rise

One of the factors behind sea level rise is the increase in temperature. When the planet warms, the oceans absorb a significant portion of this energy, and the heated water expands to occupy more space.

This process causes the ocean to rise even without the input of new water. Thermal expansion, therefore, appears as one of the central components of the change observed since the beginning of the 20th century.

Another important factor is the melting of land ice. Glaciers and large ice sheets, such as those in Greenland and Antarctica, contribute to increasing the volume of water reaching the oceans.

A 2020 analysis of the causes of sea level rise since 1900 identified ice loss as a relevant factor. Ocean warming also appears as an essential part of this process.

Land subsidence amplifies risk in coastal cities

In many coastal cities, sea level rise represents only part of the problem. The risk increases when the ground also sinks, reducing the distance between urban areas and the water surface.

In some regions of Shanghai, the ground sank by more than 90 centimeters during the 20th century. The process occurred largely due to intense groundwater extraction, causing the city to get closer to the water even before considering the ocean’s rise.

This phenomenon is called subsidence. It can occur naturally in soils formed by soft sediments, but it can also be accelerated by groundwater withdrawal and the weight of dense constructions.

Yucheng Lin, currently a scientist at CSIRO, Australia’s national research agency, stated that Shanghai is no longer sinking as fast. The change occurred after the city began to tighten rules for groundwater use.

Chinese deltas concentrate vulnerability

Many of China’s coastal megacities are located in river deltas, areas formed by thick, waterlogged sediments. These sediments compact over time, increasing vulnerability with intense urbanization.

The study highlights the Yangtze River Delta and the Pearl River Delta. These regions combine low altitude, accelerated growth, and strong industrial activity, characteristics that increase exposure to floods.

The risk is not limited to China. Researchers also cite major coastal cities such as New York, Jakarta, and Manila, situated in low-lying plains where rising waters can add to land subsidence.

This combination can turn a rare flood into a constant problem. When important productive and logistical regions become more exposed, the effects can reach transportation, supply chains, and everyday products.

Urban measures can buy time against rising waters

The research indicates that some measures can reduce part of the risk. Cities that decrease groundwater extraction or carefully return water to the subsoil can slow down land subsidence.

These actions do not eliminate sea level rise, but they can decrease the rate at which flood risk increases. In densely populated areas, buying time becomes a central part of coastal planning.

The work also includes vulnerability maps designed to identify local critical points. The proposal is to avoid treating the entire coast as if it had the same behavior, as each area can respond differently.

The research was supported by the National Science Foundation and NASA. The original study was published in the journal Nature and reinforces that groundwater management, the weight of constructions, and coastal planning are part of the urban response as sea levels continue to rise.

Sea level is rising as it hasn’t in 4,000 years, and scientists warn that China’s giant cities may face a much bigger problem than it seemed.

Rutgers University study indicates that sea level is advancing at the fastest pace in at least 4,000 years, while land subsidence amplifies the risk in China’s coastal megacities, especially in deltas characterized by low altitude, intense urbanization, and industrial activity

Sea level rises at a record pace for over a century

How researchers reconstructed the ocean’s history

Ocean heat and ice melt drive the rise

Land subsidence amplifies risk in coastal cities

Chinese deltas concentrate vulnerability

Urban measures can buy time against rising waters

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Sea level is rising as it hasn’t in 4,000 years, and scientists warn that China’s giant cities may face a much bigger problem than it seemed.

Rutgers University study indicates that sea level is advancing at the fastest pace in at least 4,000 years, while land subsidence amplifies the risk in China’s coastal megacities, especially in deltas characterized by low altitude, intense urbanization, and industrial activity

Sea level rises at a record pace for over a century

How researchers reconstructed the ocean’s history

Ocean heat and ice melt drive the rise

Land subsidence amplifies risk in coastal cities

Chinese deltas concentrate vulnerability

Urban measures can buy time against rising waters

The Soviet Union spent 22 years drilling into the Earth’s crust and reached a depth of 12,262 meters — they found water where it was thought impossible, hydrogen bubbling from the rock, granite that is 2.7 billion years old, and temperatures of 180 degrees that melted the drill bits.

Egypt wants to draw 10 million cubic meters of water from the Nile per day into the desert, irrigate a new agricultural frontier, and build a city where there is currently only sand.

Ethiopia has banned gasoline and diesel cars, placed over a hundred silent electric buses on the streets of Addis Ababa, and now aims for half a million electric vehicles by 2030, all powered by Africa’s largest dam and a courage that few countries have shown.

Norway is drilling 27 kilometers of rock 392 meters below the bottom of a fjord to build the world’s largest and deepest underwater road tunnel — when completed, a 21-hour journey will be reduced to 10.

An astronaut spent 340 days in space while his twin brother stayed on Earth, and NASA found a “rejuvenating” effect, genes, microbiome, cognition, and immune system that revealed the biological cost of living outside the planet.

After 14 years of construction and a diplomatic crisis that nearly led to a military confrontation over control of the Nile, Ethiopia inaugurated the largest hydroelectric power plant in Africa — the dam is 170 meters high, holds 74 billion cubic meters of water, and generates 5,150 megawatts.

The Brazilian city that hides a 25-million-year-old volcano in the middle of the Caatinga and holds one of the country’s rarest and most impressive geological formations

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