Negative trend halted?

Ocean temperatures without daily records again

(Bild: APA/africaimages.com)

The oceans have been setting heat records for more than 15 months - now the constant highs are probably coming to an end for the time being. On a global average, the surface temperature of the US platform "Climate Reanalyzer" was recently no longer above the previous year's daily values. According to Helge Gößling from the German Alfred Wegener Institute (AWI), it is likely that the global ocean temperature in the second half of the year will remain below the extreme records set in 2023.

The oceans have been exceptionally warm since March last year. Every single day since then, the surface temperatures of the oceans have been the highest since measurements began around 40 years ago, usually with a large gap to the previous daily record. Even now, the temperature is still well above the average for the years 1982 to 2011.

The main reason for the rise is man-made greenhouse gases. According to experts, over 90 percent of the resulting warming effect is absorbed by the oceans. Even a change of a tenth of a degree means the warming of incredibly large masses of water.

Influence of El Niño decreasing
In addition to the constant man-made warming, there have also been other effects recently. For example, the climate phenomenon El Niño pumped heat up from the depths of the Pacific Ocean. "The influence of El Niño on the globally averaged temperature is currently decreasing noticeably," explained climate physicist Gößling. The change to its counterpart La Niña - also a natural, regularly occurring climate phenomenon - is likely to lead to a drop in global temperatures. "However, it is still unclear how much cooling we can actually expect."

The AWI researcher refers to analyses according to which the influence of El Niño on the records was not too great. Experts cite other factors for the unusually sharp swings. The reduction of sulphur emissions in shipping and the eruption of an underwater volcano could have been partly responsible.

"Overall, however, these contributions appear to be too small to explain the recent rise in temperature," said Gößling. Wherever the rest comes from, the cause is crucial to the question of whether temperatures will rise in the future as previously expected - or take a different path upwards.