Earth's oceans have absorbed heat equal to 3.6 billion Hiroshima atom bombs in 25 years, finds study

2019 has been the hottest in terms of global ocean temperature and this has had disastrous effects on marine life

                            Earth's oceans have absorbed heat equal to 3.6 billion Hiroshima atom bombs in 25 years, finds study
(Getty Images)

The heat humans have put in the oceans in the last 25 years equals 3.6 billion Hiroshima atom-bomb explosions.

This is the conclusion of a new analysis that says the world's oceans were warmer in 2019 than at any other time in recorded human history, especially between the surface and a depth of 2,000 meters. 

The study, conducted by an international team of 14 scientists from 11 institutes across the world, also says that the last 10 years have been the warmest on record for global ocean temperatures, with the past five years holding the highest record.

“This paper is more dire news about the implications for humans and animals. The warming oceans are already threatening biodiversity. We see, for instance, the terrible influence on corals. But other sea life is being affected as well. For humans, the warming and rising seas are a real problem because coastal communities are being affected,” John Abraham, co-author of the study and professor of mechanical engineering at the University of St. Thomas, US, told MEA WorldWide (MEAWW).

“If we don’t do anything, it will be truly terrible, particularly for some parts of the planet. If we do something now, the situation will still be bad but not terrible. The problem is we have lost a lot of time. We have not acted for decades. We will have about 1 meter of water rise by the year 2100. I estimate that 150 million people will be displaced. This is obviously a problem in places like Bangladesh but even in places like the US and Europe. Warmer oceans are also creating more severe weather with more heavy rainfalls and flooding,” he told MEAWW.

According to Abraham, just a few years ago, there was a “lot of hope” when the US was a world leader and had forged agreements with China, India, and other countries. “But now, with President Trump in office, the US is the biggest obstacle for dealing with climate change,” he told MEAWW.

Ocean warming poses a threat to food security and people's livelihoods (Jiang Zhu)

The ocean absorbs most of the excess heat from greenhouse gas emissions, leading to rising ocean temperatures.

In the face of such disastrous effects as the 17.9 million acres Australian bushfire, which has resulted in deaths and destruction, the researchers report that global ocean temperature is not only increasing, but it is speeding up.

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, state the findings published in the Advances in Atmospheric Sciences.

“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 3.6 billion Hiroshima atom-bomb explosions." says Lijing Cheng, lead author of the study.

"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," says Cheng, an associate professor with the International Center for Climate and Environmental Sciences at the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences (CAS).

The researchers used a relatively new method of analysis from the IAP 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 meters deep. The new data allowed the researchers to examine warmth trends dating back to the 1950s. This study also includes ocean temperature changes recorded by the National Oceanic and Atmospheric Administration (NOAA) in the US. The two independent data sets indicate that the past five years have been the warmest on record for global ocean temperatures.

They found that 2019 broke the previous records set for global warming and the effects are already appearing in the form of more extreme weather, rising sea levels and harm to ocean animals.

The researchers 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 about 450% 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. The key to answering this question is in the oceans -- that's where the vast majority of the heat ends up. If you want to understand global warming, you have to measure ocean warming,” says Abraham.

Ocean temperature trend from 1960 to 2019 in the three major ocean basins from the surface to 2,000m. The zonal and vertical sections are organized around the Southern Ocean in the center. Black contours show the associated climatological mean temperature with intervals of 2 degrees Celsius. (Lijing Cheng)

The researchers say that since 1970, more than 90% of global warming heat went into the ocean, while less than 4% 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. The global ocean warming has caused marine heatwaves in the Tasman Sea and other regions,” says Cheng.

One such marine heatwave in the North Pacific, dubbed "the blob", was first detected in 2013 and continued through 2015.

"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. These manifestations of global warming have major consequences,” says Kevin Trenberth, co-author and distinguished senior scientist at the National Center for Atmospheric Research, US.

Trenberth also noted 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 according to the Rice Kinder Institute for Urban Research. The following year, a hotspot in the Atlantic Ocean near the Carolinas led to Hurricane Florence. According to Moody's Analytics, an economic research organization, the storm caused 53 deaths and between $38 and $50 billion in economic damage.

According to the researchers, humans can work to reverse their effect on the climate, but the ocean will take longer to respond than atmospheric and land environments. 

“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,” says Abraham.

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