The world’s oceans were the hottest ever recorded in 2022, with scientists blaming the high temperatures on CO2 emissions from human activities.
An international team of scientists warned the Earth’s “energy and water cycles have been profoundly altered” due to human-caused emissions and this is the cause of the “changes in the Earth’s climate system.”
The records, which started in 1958, show a huge rise in ocean temperature - with an acceleration in warming occurring after 1990.
More than 90% of the excess heat trapped by greenhouse gas emissions is absorbed in the oceans.
Analysis from the researchers found that in the past year, oceans have received an additional 10 Zetta joules (ZJ) of heat – roughly equivalent to 100 times the total electricity generated internationally in 2021.
‘Tremendous consequences all around the world’
Sea surface temperatures have a major influence on the world’s weather. Hotter oceans help to spur on extreme weather leading to more intense hurricanes and typhoons. Warmer water also pushes up sea levels and endangers coastal cities.
Prof John Abraham, at the University of St Thomas in Minnesota and part of the study team, said: “If you want to measure global warming, you want to measure where the warming goes, and over 90% goes into the oceans.
“Measuring the oceans is the most accurate way of determining how out of balance our planet is. We are getting more extreme weather because of the warming oceans and that has tremendous consequences all around the world.”
The ocean analysis published in the journal Advances in Atmospheric Sciences on Wednesday (11 January) collected observations from 24 scientists across 16 institutes worldwide.
The team of researchers used two datasets, one from China’s Institute of Atmospheric Physics (IAP), and a second from the US National Centers for Environmental Information (NCEI). Both analysed the observations of ocean heat content (OHC) and their impact dating from the late 1950s.
The heat contained in the top 2,000m (6,560 feet) of the ocean was 10 ZJ, while four ocean basins were noted for recording their highest temperature since the 1950s. These were the North Pacific, North Atlantic, the Mediterranean Sea, and southern oceans.
The researchers also collected data on ocean salt concentration, which can increase as temperatures rise. An index of the variability of salt levels across the oceans reached a record high in 2022.
Consequences of extreme heat
Last year is expected to be the fourth or fifth hottest recorded for surface air temperatures when the final data is collated.
Prof Michael Mann, at the University of Pennsylvania, part of the team of researchers said warmer oceans means there is “potential for bigger precipitation events, like we’ve seen this past year in Europe, Australia, and currently on the west coast of the US.”
He said the analysis showed an ever-deeper layer of warm water on the ocean surface: “This leads to greater and more rapid intensification of hurricanes – something we’ve also seen this past year – since the winds no longer churn up cold sub-surface water that would otherwise dampen intensification.”
The researchers also said: “There are increasing occurrences of record-shattering heatwaves and droughts in the northern hemisphere, consistent with intensive ocean warming in the mid-latitude Pacific and Atlantic oceans.”
Research released on Monday (9 January) by the US National Oceanic and Atmospheric Administration showed that many extreme weather events last year had been made more likely and more intense by the climate crisis, such as the heavy rain that caused devastating floods in Chad, Niger and Nigeria.