Extreme heat in the world’s oceans passed the “point of no return” in 2014 and has become the new normal, according to research.

Scientists analysed sea surface temperatures over the last 150 years, which have risen because of global heating. They found that extreme temperatures occurring just 2% of the time a century ago have occurred at least 50% of the time across the global ocean since 2014.

In some hotspots, extreme temperatures occur 90% of the time, severely affecting wildlife. More than 90% of the heat trapped by greenhouse gases is absorbed by the ocean, which plays a critical role in maintaining a stable climate.

“By using this measure of extremes, we’ve shown that climate change is not something that is uncertain and may happen in the distant future – it’s something that is a historical fact and has occurred already,” said Kyle Van Houtan, at the Monterey Bay Aquarium, US, and one of the research team. “Extreme climate change is here, it’s in the ocean, and the ocean underpins all life on Earth.”

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The heat content of the top 2,000 metres of the ocean set a new record in 2021, the sixth in a row. Prof John Abraham at the University of St Thomas in Minnesota, one of the team behind the assessment, said ocean heat content was the most relevant to global climate, while surface temperatures were most relevant to weather patterns, as well as many ecosystems.

“Oceans are critical to understanding climate change. They cover about 70% of the planet’s surface and absorb more than 90% of global warming heat,” Abraham said. “The new study is helpful because the researchers look at the surface temperatures. It finds there has been a big increase in extreme heat at the ocean’s surface and that the extremes are increasing over time.”

https://www.theguardian.com/environment/2022/feb/01/extreme-heat-oceans-passed-point-of-no-return-high-temperatures-wildlife-seas