Jan 12, 2022 - Energy & Environment

World ocean temperatures in 2021 were hottest ever recorded

Global ocean heat content in the upper 2,000 meters since 1940
Data: Cheng, L. J, and Coauthors, 2022; Chart: Jared Whalen/Axios

World ocean temperatures in 2021 were the hottest ever recorded by humans, according to a new peer-reviewed study.

Driving the news: The research ties the warming trend conclusively to human emissions of greenhouse gases from the burning of fossil fuels, such as coal and natural gas.

Why it matters: The oceans store at least 90% of the extra heat retained in the atmosphere from human-induced greenhouse gas emissions, and ocean warming is increasingly tied to extreme weather and climate events.

The new study — published in Advances in Atmospheric Sciences — presents the first analysis of ocean heat content through 2021 from two different data sets.

  • Each clearly shows ocean temperatures reached new heights in 2021, continuing their sharp increase during the past several decades.

Details: The study found that the period since 1985 has seen an eightfold increase in ocean heat content when compared to the 1958 to 1985 period, and each decade since 1958 has been warmer than those that preceded it.

  • Seawater expands as it warms, yielding higher sea levels, more marine heat waves that can kill sensitive coral reefs, and other ecosystem changes.
  • Warmer waters can also yield faster intensification of tropical storms and hurricanes, as was seen with Hurricane Ida last year, and help boost heavy precipitation and fuel severe weather well inland, as occurred in the Midwest during December of last year.

What they're saying: "The oceans will continue to warm until net carbon emissions go to zero. Ocean warming is destabilizing Antarctic ice shelves and threatens massive (meters) of sea level rise if we don’t act," said study co-author Michael Mann of Penn State University, in an email.

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