The amount of heat that has been added to the world’s oceans over the past 25 years is equivalent to that of 3.6 billion Hiroshima atom-bomb explosions, according to a findings released on Monday.
That measures out to approximately four Hiroshima bombs being dropped into the ocean every second over that time span, Lijing Cheng, associate professor at the International Center for Climate and Environmental Sciences at the Chinese Academy of Sciences, told CNN.
And the rate of warming in the oceans appears to be increasing.
The new study, led by Cheng, looked at ocean temperature levels since the 1950s and found that “the past five years are the top five warmest years in the ocean historically.” The last 10 years also saw the 10 warmest ocean temperatures in recorded history.
The study also looked at warming trends over two near-equal time periods, from 1955 to 1986 and 1987 to 2019, and found that the warming during the second period was approximately 450% greater than the first.
Ocean heat is a key measure of global warming. More than 90% of the earth’s heat accumulates in the oceans, the study reported.
Because the ocean is slow to change, these rates of warming will continue to increase even if global warming can be held to 2 degrees Celsius, the target of the Paris climate agreement, the study notes.
“However, the rates and magnitudes of ocean warming and the associated risks will be smaller with lower [greenhouse gas] emissions,” the study said.
Human action to reduce emissions is still essential, it concluded.
One negative effect of ocean warming is a reduction of dissolved oxygen in waters, which harms sea life, such as corals. Another effect is evaporation, which can exacerbate heavy rains, cause flooding, and drive more extreme weather events like hurricanes and typhoons. Higher ocean temperatures can also cause the ocean to expand and accelerate ice melting, further driving sea level increases.