A NASA-led study has confirmed that global sea level rise doubled in 2024, primarily driven by the record-breaking ocean warming caused by climate change. The findings have sent alarm bells ringing for coastal communities worldwide, as the accelerated rise threatens to inundate low-lying areas much sooner than previously anticipated.
According to NASA’s analysis, the global sea level rose by 0.23 inches (0.59 cm) per year in 2024, significantly exceeding the projected annual increase of 0.17 inches (0.43 cm). Since 1993, global sea levels have risen by approximately four inches (10 cm), but the rapid acceleration observed in 2024 marks a troubling departure from historical trends.
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Traditionally, sea level rise has been attributed to two main factors: the melting of ice sheets and glaciers, which contributes additional water to the ocean, and the thermal expansion of seawater as it warms. However, the NASA study revealed a stark shift in these dynamics. While ice melt typically accounted for two-thirds of sea level rise in recent years, thermal expansion was responsible for the majority of the increase in 2024.
“The rise we saw in 2024 was higher than we expected,” said Josh Willis, a sea level researcher at NASA’s Jet Propulsion Laboratory. “Every year is a little different, but what’s clear is that the ocean continues to rise, and the rate of rise is getting faster and faster.”
Earth’s oceans have reached their highest levels in three decades, according to Nadya Vinogradova Shiffer, director of NASA’s Integrated Earth System Observatory. The annual rate of sea level rise has more than doubled since satellite monitoring began in 1993, reinforcing the urgency of addressing climate change.
The phenomenon of thermal expansion is influenced by several oceanic processes. Normally, ocean waters stratify into layers based on temperature and density, with warmer, lighter water at the surface and cooler, denser water below. However, extreme weather events, powerful ocean currents, and phenomena like El Niño can disrupt this layering, allowing heat to penetrate deeper into the ocean. The 2024 spike in sea level rise is largely attributed to such vertical mixing processes, particularly in the Southern Ocean and the Pacific.
Since 1901, global sea levels have risen by six to 10 inches (15–25 cm), with the rate of increase accelerating sharply since the 1970s. The average rise of 2.3 mm per year in the latter half of the 20th century has more than doubled to 4.62 mm per year over the past decade.
The Intergovernmental Panel on Climate Change (IPCC) has projected a 52–98 cm increase by 2100, but some scientists argue that these estimates are conservative. As ice sheet destabilization accelerates, there is growing concern that the world may be underestimating the severity of the crisis.
If greenhouse gas emissions remain unchecked, NASA estimates that sea levels could rise between 5 feet 9 inches (1.75 meters) and 8 feet (2.4 meters) by 2100. Other projections estimated a 1.6–3.9 feet (0.5–1.2 meters) rise by the end of the century, but recent studies indicate the increase could be much greater due to accelerated Antarctic ice melt.
Coastal cities in danger
The projected sea level rise could pose an existential threat to major coastal cities and low-lying island nations. The United States is expected to experience sea level increases two to three times higher than the global average by the end of the century, while countries in Asia—including Indonesia, Bangladesh, and the Philippines face the inevitable dangerous exposure, leaving aside low-lying Caribbean and Pacific island nations wiping out of the world map by 2100.
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A 2018 study by researchers at Rutgers, Princeton, and Harvard found that rising sea levels could displace more than 153 million people by 2100 if emissions are not curtailed. Critical agricultural regions, such as the Nile Delta, could also be submerged, leading to severe food security crises. In a worst-case scenario, a 2-meter sea level rise could trigger mass displacement on a global scale, according to Professor Jonathan Bamber of the University of Bristol.
Though NASA’s ongoing satellite monitoring efforts, spearheaded by missions like Sentinel-6 Michael Freilich and its upcoming twin Sentinel-6B, will continue to track sea level changes with precision, experts emphasize that without drastic reductions in greenhouse gas emissions, the future of many coastal communities remains perilously uncertain.