GNV News March 21, 2025

2024 was the warmest year on record, and at the same time the rates of sea-level rise and Arctic sea-ice melt were faster than expected.

According to a NASA announcement, the rate of sea-level rise in 2024 was 0.59 cm/year, exceeding the expected 0.43 cm/year. Since satellite observations began in 1993, sea level has continued to rise, increasing by a total of 10.1 cm. Moreover, the rate of sea-level rise has been accelerating and is now twice as fast as in 1993. In recent years, about two-thirds of sea-level rise has been caused by the influx into the ocean of ice sheets and glaciers melted on land, and one-third by the thermal expansion of seawater. However, in 2024 that proportion was reversed, with the primary cause being the thermal expansion of seawater due to ocean warming.

Arctic sea ice, which is changing faster than anywhere else on Earth, is now shrinking at a rate of 12.2% per decade—six times faster than in the 1990s—and shrinking faster than expected. This acceleration is linked not only to direct ice melt from warming, but also to the retreat of Greenland’s ice sheet. According to NASA’s Arctic exploration project “ARCSIX,” it has already been shown that dust originating from Greenland’s exposed land is contributing to the melt of vulnerable sea ice in the Arctic. The additional dust released is carried by strong northerly winds and forms ice crystals in clouds aloft. Clouds reflect sunlight and help slow the rate of ice melt. However, ice crystals tend to make these clouds dissipate sooner, ultimately leaving sea ice more exposed to sunlight.

Learn more about ocean warming → 「The reality beyond 1.5°C: Global climate change issues, measures, and coverage in Japan」

Learn more about the melting of the Greenland ice sheet → 「A major decision facing the world’s largest island」

Sea ice floating on the ocean and land-based ice sheet and glaciers (Greenland) (Photo: Christine Zenino / Wikimedia Commons [CC BY 2.0])