Oceans Feel the Heat from Human Climate Pollution

Oceans have absorbed the vast majority of the warming caused by burning fossil fuels and shielded societies from the full impact of greenhouse gas emissions. But this crucial ally has developed alarming symptoms of stress – heatwaves, loss of marine life, rising sea levels, falling oxygen levels and acidification caused by the uptake of excess carbon dioxide. These effects risk not just the health of the ocean but the entire planet.

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The ocean not only stores heat, it has also taken up 20 to 30 percent of all humans' carbon dioxide emissions since the 1980s, according to the IPCC, causing the waters to become more acidic.

Acidification weakens corals and makes it harder for shellfish and the skeletons of crustaceans and certain plankton to calcify.

"Another key indicator is oxygen concentration, which is obviously important for marine life," said Melet.

Oxygen loss is due to a complex set of causes including those linked to warming waters.

Combined Arctic and Antarctic sea ice cover - frozen ocean water that floats on the surface - plunged to a record low in mid-February, more than a million square miles below the pre-2010 average.

This becomes a vicious circle, with less sea ice allowing more solar energy to reach and warm the water, leading to more ice melting.

This feeds the phenomenon of "polar amplification" that makes global warming faster and more intense at the poles, said Guinaldo.