In 2019, the world’s oceans were the warmest they’ve ever been in recorded human history, and over the past 25 years, the amount of heat we’ve put into our oceans is equivalent to the energy released by 3.6 billion Hiroshima atom bomb explosions. Scientists say the only reasonable explanation for this extent of warming is human emissions.
An international team of 14 scientists published these ocean temperature findings in a new study, which was published this week in the journal Advances in Atmospheric Sciences. These researchers looked at data from the Institute of Atmospheric Physics at the Chinese Academy of Sciences and from the National Oceanic and Atmospheric Administration dating back to the 1950s to analyze ocean temperatures between the surface and 2,000 meters deep. The past 10 years have been the warmest on record for global ocean temperatures, they concluded, and the hottest five years ever recorded have all occurred in the past five years.
Researchers also compared data from two different recording periods, and found that the ocean warming that occurred between 1987 to 2019 was 450% greater than the warming that occurred between 1955 to 1986, “reflecting a major increase in the rate of global climate change,” they write.
It may be hard to wrap our heads around how great of a difference this warming is, so the scientists put it another way: In 2019, the ocean temperature was about 0.075 degrees Celsius above the 1981 to 2010 average, and though that change may seem slight, that increase in temperature means the ocean would have taken in 228,000,000,000,000,000,000,000, or 228 sextillion, joules of heat. The Hiroshima atom bomb exploded with an energy of about 63,000,000,000,000 joules.
“This measured ocean warming is irrefutable and is further proof of global warming,” Lijing Cheng, lead paper author and professor at the Institute of Atmospheric Physics, says in a statement. “There are no reasonable alternatives aside from the human emissions of heat trapping gases to explain this heating.” This immense heat is spread throughout the world’s oceans, but the Atlantic Ocean and Southern Ocean (especially around Antarctica) have experienced more warming, compared to most of the other areas.
It’s important to pay attention to ocean temperatures, scientists say, because that’s where most of the heat on the planet is stored, and the changes in temperature are undeniable evidence of climate change. “The ocean heating is irrefutable, and a key measure of the Earth’s energy imbalance: the excess [greenhouse gases] in the air trap more heat inside the climate system and drives global warming,” the researchers write. “More than 90% of the heat accumulates in the ocean because of its large heat capacity, and the remaining heating manifests as atmospheric warming, a drying and warming landmass, and melting of land and sea ice.” There is no other explanation for this warming than the man-made release of heat-trapping gases into our atmosphere, the scientists say.
But just because most of the heat went into the oceans rather than affecting land doesn’t mean those of us on land aren’t impacted by this warming. “If you want to understand global warming, you have to measure ocean warming,” John Abrams, a study coauthor and University of St. Thomas professor says in a statement. A major consequence has been marine heat waves causing a dramatic loss of marine life—everything from phytoplankton to whales, and at least 100 million cod, researchers say. But even though a relatively small fraction of the heat has affected our atmosphere and land, global warming has still led to an increase in catastrophic fires like those in the Amazon and Australia, and more intense storms like Hurricane Harvey and Hurricane Florence, which each caused upwards of 50 deaths and tens of billions in economic damage.
These researchers aren’t done assessing the impacts of this warming. Next, they plan to study the effects of ocean warming on the water’s buoyancy, which they say directly affects how nutrients and heat are distributed. They also note that the ocean isn’t done warming, and we can only expect things to get worse, and at a faster and faster rate. Still, we can reverse this tide, they say, because the speed of ocean warming depends on our actions regarding climate change. “The more we reduce greenhouse gasses, the less the ocean will warm, Cheng says. “Reduce, reuse and recycle and transferring to a clean energy society are still the major way forward.”