The world’s oceans were the warmest in 2019 than at any other time in recorded human history, a new study found.
Ocean temperatures were about 0.075 degrees Celsius above the 1981-2010 average last year.
The study’s researchers calculated it would take 3.6 billion Hiroshima atom-bomb explosions to recreate such a temperature rise.
Records also showed the seas had warmed up more than four times quicker in the past three decades, than in the previous thirty years.
The surging temperatures are sparking marine heat waves, with one notorious example in the North Pacific dubbed “the blob.”
Scientists believe it decimated marine life ranging from plankton to whales and killed 100 million cod.
An international team of scientists said there were “no reasonable alternatives” to explain the trend other than heat emitted by humans.
They said the findings indicate the surging pace of global warming, because “more than 90 per cent” of heat ends up in the oceans.
Study author Professor John Abraham, at St. Thomas University, US, said: “It is critical to understand how fast things are changing.
“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.”
To reach current temperatures, the ocean would have taken in 228,000,000,000,000,000,000,000 (228 Sextillion) Joules of heat.
Chinese Academy of Sciences
Lead author Dr Lijing Cheng, associate professor at the Chinese Academy of Sciences (CAS), said: “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.”
Dr Cheng, who collaborates with researchers at CAS’s Ocean Mega-Science hub, added: “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.”
The researchers used newly-available data to examine warmth trends dating back to the 1950s.
Using two independent data sets, the National Oceanic and Atmospheric Administration (NOAA) in the United States, they discovered that the past five years have shown the warmest ocean temperatures ever recorded.
The team, whose findings were published in the Advances in Atmospheric Sciences journal today (Mon) also compared the 1987 to 2019 data recording period to the 1955 to 1986 period.
They found that over the past six decades, the more recent warming was around 450 per cent that of the earlier warming, reflecting a major increase in the rate of global climate change.
Last year’s record is already showing in the form of more extreme weather, rising sea levels and harm to ocean animals.
Professor Abraham added: “Global warming is real, and it’s getting worse. And this is just the tip of the iceberg for what is to come.
“Fortunately, we can do something about it: We can use energy more wisely and we can diversify our energy sources. We have the power to reduce this problem.”
The researchers stressed humans can work to reverse their effect on the climate, but added that the ocean will take longer to respond than the air and the land.
Since 1970, more than 90 per cent of global warming heat entered the ocean, while less than 4 per cent of the heat warmed the atmosphere and land where humans live.
Dr Cheng added: “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.
The global ocean warming has caused marine heat waves in the Tasman Sea and other regions.”
The North Pacific marine heat wave, “the blob,” was first detected in 2013 and wreaked havoc until 2015.
Study author Dr Kevin Trenberth, at the National Center for Atmospheric Research, US, said: “These manifestations of global warming have major consequences. The blob is documented to have caused major loss of marine life, from phytoplankton to zooplankton to fish — including a 100 million cod — to marine animals, such as whales.”
The climate analyst also noted that a 2017 hot spot in the Gulf of Mexico spawned Hurricane Harvey, which the Rice Kinder Institute said led to 82 deaths and caused about £83 billion ($108 billion) in damages.
The following year, a hotspot in the Atlantic Ocean near the Carolinas led to Hurricane Florence.
Financial service giant, Moody’s Analytics calculated the storm, which killed 53 people, caused damage of between £29 ($38) billion and £38 ($50) billion.
Dr Cheng added: “The price we pay is the reduction of ocean-dissolved oxygen, the harmed marine lives, strengthening storms and reduced fisheries and ocean-related economies.”
He added: “However, the more we reduce greenhouse gasses, the less the ocean will warm. Reduce, reuse and recycle and transferring to a clean energy society are still the major way forward.”
The researchers are now examining how warming impacts oceans beyond temperature, including the water’s buoyancy, which directly affects the distribution of nutrients and heat.
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