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(Peter Cade/Getty Images)
Global sea levels rose more than expected in 2024, Earth's hottest year on record, according to an analysis released Thursday by the US space agency NASA.
On its website, the National Aeronautics and Space Administration explained that last year's increase "was due to an unusual amount of ocean warming, combined with meltwater from land-based ice such as glaciers."
According to the analysis led by NASA, which monitors rising water levels using satellite imagery, the world's seas rose by 0.23 inches (0.59 centimeters) in 2024, well above the 0.17 inches (0.43 cm) predicted by scientists.
Launched in 2020, Sentinel-6 Michael Freilich is one of two satellites taking measurements of sea levels. (NASA)"Every year is a little bit different, but what's clear is that the ocean continues to rise, and the rate of rise is getting faster and faster," said researcher Josh Willis of NASA's Jet Propulsion Laboratory.
Rising sea levels are among the consequences of human-induced climate change, and oceans have risen in line with the increase in the Earth's average surface temperature – a change which itself is caused by greenhouse gas emissions.
Over a recent three-decade period, from 1993 to 2023, average sea levels around the globe have risen by some four inches (10 cm) in total, according to NASA.
This graph shows global mean sea level (in blue) since 1993 as measured by a series of five satellites. The solid red line indicates the trajectory of this increase, which has more than doubled over the past three decades. The dotted red line projects future sea level rise. (NASA/JPL-Caltech)The phenomenon is caused primarily by two factors: the melting of glaciers and polar ice caps, which increases the flow of freshwater into oceans; and the expansion of sea water due to heat, a process known as thermal expansion.
In recent years, the observed rise in sea levels has been mainly caused by the first factor and less by the second, according to NASA.
"But in 2024, those contributions flipped, with two-thirds of sea level rise coming from thermal expansion," the agency said.
The year 2024 was the warmest on record since such record keeping began in 1850.
Sea levels are expected to rise further as humanity continues to emit greenhouse gases, threatening vast populations living on islands or along coastlines.
