World’s oceans hit record-high July temperatures

The world's oceans reached record-high temperatures in July, with the average sea surface temperature hitting 20.96C, surpassing the previous high of 20.89C set in 2023. This surpasses the estimated pre-industrial average by 1.47C, according to the Copernicus Climate Change Service. The EU's climate monitoring service attributes this rise, in part, to developing El Niño conditions in the Pacific.

Meanwhile, Western Europe endured its hottest June and July on record, aggravating extreme wildfires across the region. The UK braces for its fifth heatwave of the year, as persistent dry weather exacerbates water supply pressures and drought conditions. Along the Atlantic coast and in the western Mediterranean, sea surface temperatures in July reached record highs, leading to widespread strong and severe marine heatwaves.

Elsewhere, the tropical Pacific saw exceptionally high sea temperatures due to El Niño, a natural weather pattern that, combined with human-induced global warming, can cause temperature spikes and more extreme weather. As oceans absorb most of the excess heat from greenhouse gas emissions and produce half of Earth's oxygen, their warming has significant implications.

The primary effect of ocean warming is sea level rise, as thermal expansion accounts for roughly a third of recorded sea level rise. This encroaching water threatens low-lying coasts and island nations. Additionally, warmer seas intensify marine heatwaves, causing mass coral bleaching and decimating kelp forests and fisheries. Warmer ocean surfaces also evaporate more heat and moisture, intensifying tropical storms and increasing rainfall.

Samantha Burgess, strategic lead for climate at the European Center for Medium-Range Weather Forecasts, notes that Western Europe's exceptional heat is due to persistent high-pressure systems trapping heat and reduced natural cooling from dry soils. In the UK, a fifth consecutive heatwave and record-breaking temperatures have heightened concerns over water supplies and drought conditions.

The Met Office reports that England and Wales experienced their driest July in 190 years, officially declaring several areas in drought. As El Niño may further raise global temperatures, scientists emphasize the increasing normality of extreme weather, driven by both human-induced warming and natural climate phenomena.