The United Nations General Assembly adopted a declaration on sea-level rise, according to a World Meteorological Organization report published on 25 September 2026. The declaration states that the rise's cumulative, severe and irreversible risks demand stronger international cooperation and urgent, coordinated action, with adaptation and mitigation based on the best available science. It was adopted by acclamation at the high-level segment of the 81st General Assembly on 24 September, the report said.

UN Secretary-General António Guterres said sea-level rise is a threat multiplier affecting economies, trade, infrastructure and food systems. According to the report, he said around 770 million people, nearly one-tenth of humanity, live less than five metres above the high-tide line, and that without significant adaptation and mitigation, risks to coastal cities and communities are projected to increase at least tenfold by 2100. The report also cited WMO's State of the Global Climate 2025 finding that at the end of 2025 global mean sea level was around 11 cm higher than in January 1993.

The declaration stresses improved data availability, risk assessments, early warning systems and long-term planning, and commits to strengthening coordinated scientific observation and exchange. WMO welcomed it, noting gaps in observations, particularly across the oceans, in small island developing States and other vulnerable coastal regions.