When we think of the climate crisis, the first thing we usually think of is the way that global air temperatures are rising. However, what is often less talked about is the way that climate change is affecting the world’s oceans. After all, the global ocean plays a crucial role in regulating our planet’s temperature. As has been amply demonstrated by climate science, it’s the oceans that first absorb the excess heat generated by our burning of fossil fuels like oil and coal. Since the 1970s, more than 90% of the heat has been absorbed by the global ocean. It’s only relatively recently that we’re seeing the results of global warming in the atmosphere. The situation of the oceans is much worse.
An important new analysis, published on Monday in the journal Advances In Atmospheric Sciences, puts this into greater relief. The paper, Another Year Of Record Heat For The Oceans,shows that in 2022, the global ocean was hotter than it has ever been.And this spells danger for the entire planet. The analysis, prepared by an international team of scientists, found that in 2022, the top 2,000m of the ocean absorbed 10 zettajoules more heat than in the previous year. This is an enormous amount of energy, equal to 100 times the amount of electricity generated across the world in 2021. A scarier equivalent is the energy released by five Hiroshima atomic bomb explosions, every second of every hour, for 365 days a year.
Here we have a live event for 2022 ocean heat content, salinity and stratification record, Kevin Trenberth, Tim Boyer and myself will present the changes and consequences. Feel free to join in: https://t.co/RCEHfdXYsX pic.twitter.com/0rsGqSd6Kt— Lijing Cheng (@Lijing_Cheng) January 12, 2023
Unnaturally hot oceans play an important and adverse role in heightening climate impacts, like more intense cyclones, heatwaves, or more uneven and destructive rainfall events. As the analysis points out, hotter oceans also mean that the salinity of ocean water increases, which, among other things, leads to coral bleaching. A more saline ocean also means less oxygen in the water, which means fewer nutrients. This, in turn, has a huge impact on ocean fish stocks. According to the analysis, the “salinity-contrast index, a quantification of the “salty gets saltier–fresh gets fresher” pattern, also reached its highest level on record in 2022.”
The scientists say that this stratification, where the cooler waters below 2,000m don’t mix with the warmer upper layer, due to excessive heat and salinity, “has important scientific, societal and ecological consequences.” One of the co-authors of the report climate scientist and author Michael E. Mann told France 24 that, “The oceans are absorbing most of the heating from human carbon emissions. 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.” However, while global emissions need to be falling at a rapid rate, they are instead rising. A World Meteorological Organization report from October 2022 warned that the world is headed in the wrong direction, as levels of atmospheric greenhouse gases like carbon dioxide and methane are now at a record high.