Tuesday, January 25

The highest ocean temperatures in history recorded last year | oceans


The world’s oceans have simmered, and the heat is increasing. Last year saw the highest ocean temperatures in recorded history, the sixth year in a row that this record has been broken, according to new research.

The warming of our oceans is being driven primarily by the man-made climate crisis, scientists say, and represents an absolutely simple indicator of global warming. While the temperature of the atmosphere is also trending strongly upward, individual years are less likely to break records compared to warming oceans.

Last year a record heat was recorded in the upper 2,000 meters of all the world’s oceans, despite an ongoing La Niña event, a periodic climatic feature that cools the waters of the Pacific. The 2021 record beats a modern record period dating back to 1955. The second hottest year for the oceans was 2020, while the third was 2019.

Graph of the five hottest years for the global ocean, all of which occurred between 2017 and 2021.

“The ocean’s heat content is steadily increasing globally, and this is a leading indicator of human-induced climate change,” said Kevin Trenberth, a climate scientist at the National Center for Atmospheric Research in Colorado and a co-author of the research. published in Advances in Atmospheric Sciences.

Warmer ocean waters are helping to overwhelm storms, hurricanes and extreme rains, the document states, increasing the risks of severe flooding. Heated ocean water expands and you eat in the vast ice sheets of Greenland and Antarctica, which are collectively shedding about 1 trillion tons of ice a year, with both processes fueling sea level rise.

The oceans absorb about a third of the carbon dioxide emitted by human activity, causing them to acidify. This degrades coral reefs, home to a quarter of the world’s marine life and a provider of food. for more than 500 million people, and can be harmful to individual species of fish.

As the world warms from the burning of fossil fuels, deforestation, and other activities, the oceans have borne the brunt of the additional heat. More than 90% of the heat generated in the last 50 years has been absorbed by the oceans, helping to temporarily save humanity and other terrestrial species from already catastrophic temperatures.

The amount of heat absorbed by the oceans is enormous. Last year, the upper 2,000 meters of the ocean, where most of the warming occurs, absorbed 14 more zettajoules (a unit of electrical energy equivalent to one sextillion joules) than in 2020. This amount of additional energy is 145 times greater than the world’s total electricity generation, which, by comparison, is about half a zettajulio.

Long-term ocean warming is strongest in the Atlantic and South Oceans, the new research claims, although the North Pacific has seen a “dramatic” increase in heat since 1990 and the Mediterranean Sea posted a clear record high temperature last year. .

The warming trend is so pronounced that it is clear to determine the footprint of human influence in just four years of records, according to John Abraham, another of the study’s co-authors. “The heat content of the ocean is one of the best indicators of climate change,” added Abraham, an expert in thermal sciences at the University of St Thomas.

“Until we reach net zero emissions, that warming will continue and we will continue to break records for ocean heat content, as we did this year,” said Michael Mann, a climate scientist at Pennsylvania State University and another of 23 researchers who worked on paper.A better awareness and understanding of the oceans are the basis of actions to combat climate change ”.


www.theguardian.com

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