Global warming 'equal to 25 billion nuclear bombs'

Global warming has added the energy equivalent to 25 billion nuclear bombs to the Earth system in 50 years, scientists have found.

Almost all of this heat – 89% – is stored in the ocean, compared to around 6% on land and 1% in the atmosphere, their research shows.

Andrew King, senior lecturer in climate science at the University of Melbourne, wrote in The Conversation: "Billions of nuclear bombs to produce 1.2C of heating – so what? It seems small, considering how much temperature varies on a daily basis. (The world's average surface temperature in the 20th century was 13.9C.)

"But almost all of this energy to date has been taken up by the oceans. It's no wonder we're seeing rapid warming in our oceans."

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Much of the 'excess heat' stored in the North Atlantic is in the deep ocean, at depths of below 2,300 feet, research showed last year.

The researchers say that oceans have absorbed most of the warming caused by humans – and will warm by a further 0.2C in the next 50 years.

The study found that in the sub-tropical North Atlantic, 62% of the warming from 1850 to 2018 is held in the deep ocean.

But reversing ocean warming may be difficult and time-consuming, King warns.

He said: "It takes a long time to get this much heat into the oceans, and once it is there it doesn't disappear.

"Reversing global warming entirely may not be feasible. Just to stop temperatures going any higher means correcting the imbalance and bringing CO2 levels down towards the pre-industrial level of 280 parts per million."

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Ocean warming can have a range of consequences including sea-level rise, changing ecosystems, currents and chemistry, and deoxygenation.

But the changes wrought by global warming could also have important effects for people, King says.

King said: "To warm the entire planet takes an extraordinary amount of extra energy. But now, we are at very real risk of pushing ourselves outside of the comfortable climatic conditions which allowed humans to expand, farm, build cities and create.

"The energy dense fuels which made industrial civilisation possible come with an enormous sting in the tail. Burn now, pay later. Now the bill has become apparent."

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