Are ocean temperatures staying near record highs as carbon dioxide rises?
Core argument: Atmospheric CO₂ peaked globally at a mean of 426 parts per million in March, up from 423 ppm a year earlier, and surpassed 430 ppm at the Mauna Loa Observatory in Hawaii.
The world’s ocean temperatures reached the second-highest level on record for May, capping an “alarming” two-year streak of rapid warming and fueling concerns about the seas’ ability to absorb rising levels of carbon dioxide. The EU’s Earth observation service Copernicus said the global average sea surface temperature in May was 20.79C, 0.14C below the record in the same month in 2024. The level of CO₂ in the atmosphere peaked globally at the mean of 426 parts per million in March, up from 423 ppm a year ago, and surpassed 430 ppm at the Mauna Loa Observatory in Hawaii. Scientists estimate the ocean has absorbed between a quarter and about 30% of carbon dioxide released into the atmosphere and about 90% of excess heat, helping to keep temperatures on land cooler. But Michael Meredith, a scientist at the British Antarctic Survey in Cambridge, warned the ocean “may lose some of its capacity to buffer us against the worst extremes of climate change” by absorbing less warmth or carbon than previously. “We’re seeing stronger and stronger bursts of ocean warming — marine heatwaves — that are pushing us past records at an alarming rate.”

