The world's oceans were the warmest in 2019 than any other time in the recorded human history -- especially between the surface and a depth of 2,000 metres, an international team of 14 scientists from 11 institutes has revealed, with a warning that global ocean temperature is not only increasing but speeding up.
The past 10 years were the warmest on record for global ocean temperatures, with the past five years holding the highest record, said the authors in the study published in the journal Advances in Atmospheric Sciences -- with a call to action for humans to reverse climate change.
2019 broke the previous records set in prior years for global warming, and the effects are already appearing in the form of more extreme weather, rising sea levels and harm to ocean animals.
According to the study, the 2019 ocean temperature is about 0.075 degrees Celsius above the 1981-2010 average. To reach this temperature, the ocean would have taken in 228,000,000,000,000,000,000,000 (228 Sextillion) Joules of heat.
"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 Joules. The amount of heat we have put in the world's oceans in the past 25 years equals to 3.6 billion Hiroshima atom-bomb explosions," elaborated Lijing Cheng, lead paper author at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS).
"This measured ocean warming is irrefutable and is further proof of global warming. There are no reasonable alternatives aside from the human emissions of heat trapping gases to explain this heating," Cheng added.
The researchers used a relatively new method of analysis to account for potentially sparse data and time discrepancies in instruments that were previously used to measure ocean warmth, especially from the ocean surface to 2,000 metres deep.
The newly available data allowed the researchers to examine warmth trends dating back to the 1950s.
They found that over the past six decades, the more recent warming was over 450 per cent that of the earlier warming, reflecting a major increase in the rate of global climate change.
"It is critical to understand how fast things are changing," said John Abraham, co-author and professor of mechanical engineering at the University of St. Thomas in the US.
"The key to answering this question is in the oceans -- that's where the vast majority of heat ends up. If you want to understand global warming, you have to measure ocean warming."
Humans can work to reverse their effect on the climate, but the ocean will take longer to respond than atmospheric and land environments.
Since 1970, more than 90 per cent of global warming heat went into the ocean, while less than 4 per cent of the heat warmed the atmosphere and land where humans live.
"Even with that small fraction affecting the atmosphere and land, the global heating has led to an increase in catastrophic fires in the Amazon, California and Australia in 2019, and we're seeing that continue into 2020," Cheng said.
The global ocean warming has caused marine heat waves in Tasman Sea and other regions.
One such marine heat wave in the North Pacific, dubbed "the blob," was first detected in 2013 and continued through 2015.
Kevin Trenberth, co-author and distinguished senior scientist at the National Center for Atmospheric Research in the US, said that a hot spot in the Gulf of Mexico in 2017 spawned Hurricane Harvey, which led to 82 deaths and caused about $108 billion in damages.
"The price we pay is the reduction of ocean-dissolved oxygen, the harmed marine lives, strengthening storms and reduced fisheries and ocean-related economies," Cheng said.
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