2024 was not only the hottest year ever recorded on the surface of land and oceans. Another figure, a direct consequence of global warming, is alarming scientists. On Thursday 13 March, NASA announced a resulting rise in sea levels greater than anticipated.

Sea levels rose by 0.59 centimetres against the expected 0.43

The US space agency explained that sea levels across the world rose by an average of 0.59 centimetres. This compares to an estimate made by the scientists themselves of "only" 0.43 centimetres. Why did such a significant discrepancy occur? Because, NASA's analysis explains, the gap was produced by the combination of two factors occurring simultaneously: on one hand, the melting of glaciers and polar ice caused by the excessive heat recorded repeatedly in the Arctic and Antarctic regions, as well as in alpine areas. On the other, an unexpected increase in the warming of ocean waters.

The melting of ice, in fact, obviously increases the quantity of fresh water present in the world's seas. In the last two years alone, the glaciers of the Alpine arc have lost 10 per cent of their volume. So much so that glacier melt even forced a redrawing of the border between Italy and Switzerland at the foot of the Matterhorn, among the highest peaks in Europe. At the same time, the rise in ocean temperatures also causes a thermal expansion of water: a phenomenon that scientists say is responsible for "two thirds of sea level rise".

A rise of 50 centimetres by 2050 is at risk

Josh Willis, a researcher at NASA's Jet Propulsion Laboratory, explained that "every year is a little different from the last, but what is clear is that ocean levels continue to rise and that the pace of that rise is getting faster and faster". The long-term data, moreover, leaves no room for doubt or interpretation: over the thirty years between 1993 and 2023, sea levels rose by 10 centimetres.

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Sea level update 🌊

In 2024, global sea level rose faster than expected mostly due to ocean water expanding as it warms, or thermal expansion. According to a NASA-led study, 2024's rise was 0.23 in (0.59 cm) per year, compared to the expected rate of 0.17 in (0.43 cm) per year.

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All of this will have an enormous impact above all on the populations living in numerous coastal areas around the world. Sea level rise, taking into account current trends and the fact that humanity has not achieved the necessary reduction in greenhouse gas emissions, could reach 50 centimetres by the middle of this century. "The projected rise will result in a multiplication of coastal flooding, unless adequate adaptation measures are introduced," NASA itself noted.

Almost one billion people at risk worldwide

Globally, the total number of people exposed to the phenomenon is almost one billion. A problem that will be particularly complex to address for certain Asian areas, given that some coastal zones are densely populated.