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Ocean warming reaches new record over the past five years due to climate change

Ocean warming has risen to record highs over the last five years: just in 2019 the heat released into the world’s oceans was equivalent to that of 5-6 atomic bombs per second. The culprit, no doubt, is climate change.

The world’s oceans have never been as warm as in 2019 according to the findings of a study published on the 13th of January in the journal Advances in Atmospheric Sciences. According to it, the last decade was characterised by record high temperatures, especially in the last five years. Furthermore, the authors expressed no doubts about the cause of the phenomenon: climate change is heating up the world’s oceans dramatically.

Immediate action: an appeal from the study’s authors

Unsurprisingly, the paper’s authors launched an appeal calling for urgent action to reverse the trend in the coming years. Failing this, the consequences will be nefarious both for marine biodiversity and human beings.

In particular, the study shows that ocean warming took place gradually between 1955 and 1986, but the process intensified by 4.5 times between 1987 and 2019 compared to the preceding period. For example, last year ocean temperatures were 0.075 degrees higher than the average between 1981 and 2010. This might seem like a small change, but it actually means that the oceans have absorbed an immense amount of heat from the atmosphere.

Ocean warming, “like 5-6 atomic bombs in the sea a second”

The absorbed heat is equivalent to an inconceivable 228 sextillion (or trillion billion) joules. The study’s main author, Lijing Cheng, expanded on this in a press release: “That’s a lot of zeros indeed. To make it easier to understand, I did a calculation. The Hiroshima atom bomb exploded with an energy of about 63,000,000,000,000 (63 trillion) joules. The amount of heat we’ve put in the world’s oceans in the past 25 years equals to 3.6 billion Hiroshima … explosions”. Comparable to setting one off in the world’s oceans every second.

And the process is constantly accelerating. John Abraham from the University of St. Thomas, Minnesota, told CNN that “we’re now at five to six Hiroshima bombs of heat each second”. In more down to earth terms, the amount of heat released into the oceans in 2019 was equivalent to that of every person on the planet switching on 100 microwave ovens 24/7.

All of this raises major concerns with regards to climate change. The oceans cover three quarters of the Earth’s surface and they’re responsible for absorbing 90 per cent of excess heat produced by human activities. At the same time, they also absorb large amounts of CO2 emissions, which are gradually making their waters more acidic, with grave consequences for coral reefs and many animal species.

Read more: Chasing Coral, the documentary on coral reefs that makes us all feel involved

2019 ocean warming hottest year
2019 was the hottest year on record for our oceans © Johny Goerend/Unsplash

Oceans absorb 90 per cent of excess heat from the atmosphere

Furthermore, the increase in ocean temperatures also accentuates the melting of polar ice caps, as well as changing the amount of oxygen in the water, especially at certain depths. Oxygen levels are actually decreasing in seawater: a report by the IUCN (International Union for Conservation of Nature) published in December 2019 shows that the amount of this gas in the sea decreased by 2 per cent between 1960 and 2010. And forecasts suggest a further 3-4 per cent decrease by the end of the century if emissions continue increasing at the current pace.

This will favour the proliferation of species that tolerate hypoxia (microbes, jellyfish and some squids) and negatively affect those who suffer from it (as is the case for most fish). The IUCN publication also highlights the serious consequences that the absence of oxygen can have on marine mammals, corals and mangroves.

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