Researchers from the National Center for Atmospheric Research and the Chinese Academy of Sciences have found that the world’s oceans may have 13 percent more heat than previously estimated, a new study in Science Advances reports.
These findings give insight into how temperatures have changed since 1960 and show that most heat trapped on Earth by greenhouse gas emissions is stored inside the oceans. While this is in line with past research, limited observations have made it hard to measure accurately how ocean heat content has changed over time.
In the past, scientists used ships to keep track of water temperatures. Though that method works, it limits data to the area where the ships travel. As a result, in recent years scientist have deployed a network of thousands of floats — known as Argo — to profile conditions in the top layer of the oceans.
This gave researchers an almost complete view of the Earth’s waters. To fill in any historical gaps, the team in the study combined statistical techniques with model data to determine how well a single observation can be used to analyze the area around it.
They found that, in most regions, a single observation can give key information for areas over 1,243 miles away. To show this, the team chose data from a small number of floats around the world and then used their new technique to create an ocean temperature map. The results were very close to actual temperatures.
“The results were remarkable,” said study co-author Kevin Trenberth, a researcher at the National Center for Atmospheric Research, according to Phys.org. “They give us much more confidence about what the ocean heat content was, stretching back to the late 1950s.”
Using this technique, the team estimates that the ocean warmed 337 zettajoules (a measure of energy) between 1960 and 2005. In addition, there were almost no significant temperature changes until 1980 — when ocean heat began slowly to increase each year — and heat began to permeate the deep ocean in 1990.
This new research is important because it reveals the importance of both observations and models. If scientists can develop better methods of gathering data it could help understand the past, which could then shed light on the future.
“[T]his work is an example of how advances in technology have enabled an improved understanding of past changes in the ocean, where variability has always been a bit of an enigma due to its vastness and depth,” said study co-author John Fasullo, a scientist at the National Center for Atmospheric Research, in a statement. “The insights associated with this work change not only our understanding of past climate but also how future changes might unfold.”