Record-breaking marine heatwaves caused global devastation in the last two years: Study

Mumbai: Lethal marine heatwaves during 2023-2024 had severe global impacts, triggering mass coral bleaching, collapsing fisheries, intensifying storms, and disrupted weather patterns besides damaging billions, according to a 'Nature Climate Change', a peer-reviewed scientific journal published by London-based Nature Portfolio.

The ocean plays vital roles in regulating the climate, supporting marine life, and providing food and jobs for billions of people. However, the researchers say that as marine heatwaves worsen with climate change, these functions are at risk.

The study found that there were nearly 3.5 times the number of marine heatwave days in the summers of both 2023 and 2024 compared to any other year on record. In the past two years climate change, exacerbated by El Niño, caused multiple record-breaking marine heatwaves -- which did billions of dollars of damage around the world.

This study found that in 2023-24, nearly 10 percent of the ocean hit record-high temperatures. In this comment article, scientists summarise the devastating consequences for coral reefs, fisheries, and coastal communities.

They warn that as long as the rate of human-induced climate change keeps rising, marine heatwaves will continue to worsen, and that more proactive action is needed to avert the damage that extreme ocean temperatures already cause.

A marine heatwave fuelled Cyclone Gabrielle in New Zealand in 2023, which killed 11 people and caused damage of over $8 billion. Climate change increased the intensity of the rainfall by at least 10%.

Marine heatwaves caused Peruvian anchovies to move away from their usual waters,

leading to the closure of commercial fisheries in 2023 and 2024 with estimated losses of $1.4 billion. Nearly 6,000 people died in Libya in 2023 when heavy rains from Storm Daniel caused the collapse of the Derna Dam -- the deadliest single flood event on record in Africa. Storm Daniel was made more intense and rainy due to sea temperatures made higher by climate change.

While El Niño exacerbated marine heatwaves in 2023-24, previous research showed that human-induced climate change already caused a 50 per cent increase in marine heatwaves between 2011 and 2021.

As per the study, if we keep burning fossil fuels and cutting down forests, marine heatwaves could be 20-50 times more frequent and ten times more intense by the end of the century. Replacing oil, coal and gas with renewable energy is therefore vital to safeguard ocean life and coastal communities.

“The number of impacts we have seen from marine heatwaves over the past two years have been pretty crazy, with the mass coral bleaching, species popping up in new locations and the number of related extreme weather events on land,” said Dr Kathryn E Smith, The Marine Biological Association of the United Kingdom.

“Going forward, only by reaching net zero emissions can we eventually halt this temperature increase and worsening marine heatwaves -- and we are a long way from achieving that,” said Associate Professor Alex Sen Gupta at the University of New South Wales.