The world’s oceans were the warmest on record in 2022, demonstrating the deep and wide-ranging changes human-caused emissions are causing to the planet’s climate. Long-term ocean trends show that the Atlantic and Southern Oceans absorb the most heat from our greenhouse gas emissions. Warming ocean waters contribute to an increase in storms, hurricanes, and extreme rainfall events, increasing the risk of flash floods, tidal surges, and sea-level rise.
More than 90% of the excess heat captured by greenhouse gas emissions is absorbed by the oceans. Records beginning in 1958 show a relentless rise in ocean temperatures, with warming accelerating after 1990.
Ocean surface temperature has a major impact on the world’s weather conditions. Warmer oceans promote extreme weather events, leading to more intense hurricanes and typhoons, and more moisture in the air, leading to more intense rainfall and flooding. Warm water also expands, raising sea levels and threatening coastal cities.
Ocean temperatures are less affected by natural climate variability than atmospheric temperatures, making the oceans an undeniable indicator of global warming.
2022 is the record year for the seventh time
When the final data is compiled, 2022 is expected to be the fourth or fifth warmest year on record for surface air temperature. In 2022, we witnessed the third consecutive La Nina episode, the coldest phase of an irregular climate cycle centered in the Pacific Ocean and affecting global weather patterns. When El Nino returns, global atmospheric temperatures will be even higher.
The international team of scientists preparing a new analysis of ocean warming concludes their research as follows: “Due to the emission of greenhouse gases caused by human activity, the Earth’s energy and water cycles have radically changed and caused profound changes in the Earth’s climate system. »
Professor John Abraham, from the University of St Thomas in Minnesota and a member of the research team, said: “If you want to measure global warming, you have to measure where the warming is going, and more than 90% is going to the oceans. . “Measuring the oceans is the most accurate way to determine the imbalance of our planet.
“Extreme weather patterns are on the rise due to warming oceans, with far-reaching consequences around the world. Professor Michael Mann of the University of Pennsylvania, a member of the team, said: “Warming oceans mean there is more potential for larger rain events. United States. »
According to him, the analysis shows a deeper and deeper layer of warm water at the surface of the ocean: “This leads to stronger and faster hurricanes – we saw this last year – because the winds are not blowing colder underground water. this would otherwise stop the intensification. »
The study was published this Monday, January 9 National Oceanic and Atmospheric Administration It showed that many extreme weather events in 2022 are more likely and exacerbated by the climate crisis, such as heavy rains that caused devastating floods in Chad, Niger and Nigeria.
Reliable measurements of ocean temperatures date back to 1940, but it is likely that the oceans are currently at their warmest level in 1,000 years and are warming faster than at any time in the past 2,000 years.
Heat, saltiness, layering: an explosive cocktail
The analysis was published in the journal Advances in Atmospheric Sciencesbased on temperature data collected by a range of instruments in the oceans and combined separate analyzes by Chinese and American teams to calculate the heat content of the highest 2,000 meters, where warming is greatest.
The oceans absorbed about 10 zettagulas more heat in 2022 than in 2021, which is equivalent to five more Hiroshima bombs detonating per second, 365 days a year, 24 hours a day.
The researchers also analyzed salinity, which along with temperature determines water density and is an important factor in ocean circulation. The ocean salinity variability index reached a record high in 2022, indicating a continued strengthening of the global hydrological cycle.
Another important feature of the oceans is the stratification of water according to its density. This limits mixing of deeper, colder, nutrient-rich waters with surface waters. According to the scientists, the long-term trend of stratification continued until 2022, with “significant scientific, social and environmental consequences”.
One such consequence, Ibrahim said, is that reduced mixing in the ocean means the surface layer absorbs less carbon dioxide from the atmosphere, increasing global warming.
The researchers also said: “We are seeing more record-breaking heat waves and droughts in the Northern Hemisphere, consistent with intense warming of the mid-latitude Pacific and Atlantic oceans. »
Ocean warming and its consequences for extreme weather events will intensify until humanity reaches net zero emissions.
In October, the World Meteorological Organization reported that atmospheric concentrations of all major greenhouse gases – carbon dioxide, methane and nitrous oxide – had reached record levels. “We are going in the wrong direction,” said Professor Petteri Taalas, head of the World Trade Organization.
With The Guardian / Covering Climate Now