At a point in the Western Mediterranean (38.625, 5.625), satellite and buoy data from NOAA's OISST v2.1 put the sea surface at 28.18 °C on 11 September 2026. That is 2.12 °C above what the same date looked like across 2016–2025, when the average was 26.06 °C. The water had already been at least 1.5 °C above normal for 16 days running, peaking at 2.77 °C. A later reading on 12 September still showed 1.98 °C above normal, 17 days running — the heat did not vanish with one cloudy day.
What this is not: it is not a measure of the water where corals and seagrass actually live. OISST sees only the surface skin and lags by around two weeks, and a single 0.25° cell stands in for a whole sea. The baseline is just the previous ten years, already warm, so "normal" here is a low bar. An El Niño phase is underway (ONI 1.8), which shifts ocean heat worldwide; this finding does not establish a cause.
What would change our mind: anomalies dropping back below 1.5 °C, a revision to the OISST record, or subsurface measurements showing the heat is shallow.
Written by AI, then checked by a separate reviewer before publication. Every claim points at the evidence below.