The world’s oceans last year were warmer than at any point in recorded human history — and heated so quickly that they absorbed the equivalent of nearly 4 billion atom bombs of heat in just 25 years, according to a study published Monday.
The oceans’ average temperature last year was about 0.075 degrees Celsius warmer than the 1981-2010 average. Given the enormous scale of the world’s oceans, and the short amount of time in which that level of warming occurred, the increase in temperature could only be achieved with 228 sextillion joules of heat, a figure with 21 zeros.
"That's a lot of zeros indeed,” the study’s lead author, Lijing Cheng, an associate professor with the International Center for Climate and Environmental Sciences in China, said in a statement.
By comparison, the atom bomb that exploded over Hiroshima in 1945 emitted 63 trillion joules of energy.
“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,” Cheng said, a scale of warming that can only have been caused by human activity. "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 results, which were gathered by measuring ocean temperatures from the surface to a depth of 2,000 feet, were published in the journal Advances in Atmospheric Sciences. They showed that the past decade has been the warmest on record for ocean temperatures, with the warmest period occurring in just the past five years.
The study, produced by more than a dozen scientists at 11 institutions around the globe, comes as thousands of firefighters in Australia continue to battle catastrophic wildfires that are believed to have killed more than 1 billion animals and over two dozen people, as well as burned more than 18 million acres. Australia in 2019 experienced its hottest and driest year on record, conditions that turned swaths of the country into a tinderbox and are exacerbating the current blazes — and are consistent with the impacts of climate change.
“In the face of such disastrous effects,” the paper’s authors, in statements accompanying their study, issued a “call to action for humans to reverse climate change,” even releasing the study early to underscore its urgency.
"Global warming is real, and it's getting worse," John Abraham, a study co-author and professor of mechanical engineering at the University of St. Thomas in Minnesota, said in a statement. "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."