Extreme heat in oceans ‘passed point of no return’ in 2014

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."

Van Houtan and his colleague Kisei Tanaka are ecologists and began the study because they wanted to assess how heat extremes were related to the loss of kelp forests off the coast of California.

"Ecology teaches us that extremes have an outsized impact on ecosystems," Van Houtan said. "We are trying to understand the dramatic changes that we've seen along our coasts and in the ocean, on coral reefs, kelp, white sharks, sea otters, fish, and more."

Other scientists reported in 2019 that the number of heatwaves affecting the planet's oceans had increased sharply, killing swathes of sea life like "wildfires that take out huge areas of forest".