Story at a glance
- Researchers published a new study that detailed how the world’s oceans recorded the hottest temperature in history last year.
- Increased concentration of greenhouse gases in the atmosphere from human activities traps heat within the climate system and has driven unprecedented increases in ocean heat content.
- As oceans warm, the water expands which then causes sea levels to rise.
The world’s oceans recorded the hottest temperatures in history in 2021, and scientists are ringing the alarm on the consequences of human-caused climate change.
In a report published this week, authored by 23 researchers at 14 different institutions, scientists say the increased concentration of greenhouse gases in the atmosphere from human activities traps heat within the climate system and has driven unprecedented increases in ocean heat content. The amount of outgoing energy from the Earth system is so high it’s surpassing the incoming solar radiation, creating Earth’s Energy Imbalance.
That imbalance has caused the Earth’s oceans to record alarmingly hot temperatures over the past five years, and in 2021, the world’s oceans set a new record by reaching the hottest temperature ever recorded by humans.
The recording breaking hot temperature in 2021 came despite La Niña conditions, a climate pattern that causes a cold event where winds are stronger than usual and more warm air is pushed towards Asia. In the Americas, it means more cold, nutrient-rich water is pushed to the surface.
In a press release, researchers explained that for the last year the upper 2,000 meters in all oceans absorbed 14 more zettajoules, a unit of electrical energy, than in 2020. That's equivalent to 145 times the amount of electricity generated in the world in 2020.
All of the energy humans use the world over in a single year is only about half of a single zettajoule.
“As well as absorbing heat, currently, the ocean absorbs 20 to 30% of human carbon dioxide emissions, leading to ocean acidification; however, ocean warming reduces the efficiency of oceanic carbon uptake and leaves more carbon dioxide in the air,” said Lijing Cheng, lead paper author and associate professor with the International Center for Climate and Environmental Sciences.
John Abraham, professor of thermal sciences at the University of St. Thomas and one of the co-authors of the new study, published an opinion piece in The Guardian that said the heat absorbed by the oceans last year was equivalent to seven Hiroshima atomic bombs detonating each second, 24 hours a day for 365 days a year.
"If you want to know how fast climate change is happening, the answer is in the oceans,” said Abraham.
Researchers said long-term ocean warming is happening strongest in the Atlantic and Southern oceans, while the north Pacific has had a “dramatic” increase in heat since 1990. The Mediterranean Sea also indicated a high temperature last year.
The implications of ocean temperatures rising are far reaching, as researchers explained that as oceans warm the water expands, which then causes sea levels to rise. That could eventually cause changes to engineering design, building codes and modifications to coastal development plans.
Increases in extreme precipitation events are also a consequence, which researchers say are already being observed. Even the U.S. Environmental Protection Agency (EPA) has recorded consistently high extreme one-day precipitation events in the contiguous 48 states, noting that nine of the top 10 years for extreme one-day precipitation events occurred since 1996.
Warmer oceans also mean more powerful storms and hurricanes, as it creates a warmer and moister atmosphere that promotes more intense rainfall in all storms. Researchers said that also increases risk of flooding, threatening marine ecosystems and human livelihoods.
Researchers said that better awareness and understanding of ocean dynamics are fundamental in combating climate change.
“Until we reach net zero emissions, that heating will continue, and we’ll continue to break ocean heat content records, as we did this year. Better awareness and understanding of the oceans are a basis for the actions to combat climate change,” said Michael Mann, professor of atmospheric science at Penn State University and one of the researchers who worked on the new study.
WHAT YOU NEED TO KNOW ABOUT CLIMATE CHANGE RIGHT NOW