Sea level rise seems a simple concept, but it is difficult to measure, as it varies from one region to another. For this reason, researchers are content to speak of the “average” rise: this would now reach 111 millimeters over the past 30 years, if we only rely on satellite observations.
There are estimates that go back further in time, based on precise surveys taken at regular intervals on the shore or on cliffs in different regions of the world. But satellites have offered the possibility of taking a “look” at the entire planet.
And in research published October 17 in the journal Communications Earth & Environmenta team from the Jet Propulsion Laboratory and half a dozen American institutions, concludes that between 1993 and 2023, this rise in average sea level even seems to have accelerated: by an average rate of 2.1 millimeters per year in 1993, in 2023 we would have gone to twice as much, or 4.5 millimeters per year.
If this trend continues, that would mean a total of 169 new millimeters in 30 years. Such a rate, the researchers cautiously write, “would represent a growing challenge for adaptation efforts.”
In a preliminary analysis published last March, NASA’s estimate was 180 millimeters in 2013 and 420 millimeters in 2023.
The extrapolation for the next 30 years is in line with the so-called “mid-range” estimates (in English, mid-range) which we found in 2021 in the most recent IPCC report. “Mid-range” meaning an estimate that is halfway between the most pessimistic and the most optimistic estimates.
Being able to rely on continuous satellite observations, the study reads, reinforces “these projections and provides an additional element of evidence”, while narrowing the range of estimates – between the most optimistic and the most pessimistic. And while giving political decision-makers something to prepare for the inevitable.
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