Global Oceans Break June Heat Records Amid Early El Niño Signs
The world's oceans have experienced the hottest June on record, with average sea surface temperatures reaching 20.98 degrees Celsius, surpassing previous highs from 2023 and 2024, according to the European Union's Copernicus Marine Service. This marks six months of nearly unprecedented marine heat in 2026, with prolonged heatwaves affecting 98% of the Mediterranean basin and breaking regional records, including a June peak of 24.3 degrees Celsius in the Mediterranean Sea. The tropical Pacific Ocean also recorded its warmest June ever at 27.26 degrees Celsius, matching the 2016 record for the first half of the year and showing intense warming near the equatorial Pacific and coasts of Peru and California.
Scientists link these extreme ocean temperatures to the early stages of the El Niño phenomenon, which is expected to intensify global ocean and atmospheric heat this year and next. Carlo Buontempo, director of the Copernicus Climate Change Service, warned that current conditions could signal "a new era leading to uncharted territory," with further temperature records likely in the coming months. El Niño, characterized by unusually warm Pacific waters, disrupts global weather patterns, increasing risks of floods, droughts, and wildfires worldwide.
The ongoing marine heatwaves have severe ecological impacts, including coral bleaching and mortality, as seen in Thailand's reefs. The warming oceans also contribute to rising sea levels through thermal expansion and fuel extreme weather by increasing atmospheric moisture. The UN recently described the oceans as being in a "deep crisis" due to warming and sea-level rise. Dr. Simon van Hanhif, chief oceanographer at Copernicus Marine, emphasized that 2026 could be among the hottest years recorded, driven by both El Niño and ongoing greenhouse gas emissions.
Overall, the extensive marine heatwaves affecting approximately 82% of the world's oceans in the first half of 2026 represent the second-largest extent after 2024. These prolonged high temperatures threaten marine biodiversity and exacerbate climate change impacts globally.
