How do scientists measure the ocean's temperature?

By Jeremy Shere

Posted April 15, 2025

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Transcript

D: It's time to go again to the A Moment of Science mailbag...

Y: A listener writes:

Dear AMOS,

I hear a lot about global warming, but how do scientists take the earth's temperature?

D: Great question. Most of the excess heat trapped by greenhouse gasses like carbon dioxide ends up in the oceans. That's because the earth's oceans are kind of like a giant sponge that can hold a lot of heat for a long time.

Y: Now, the oceans are huge--in fact they cover most of the planet. And some parts of the oceans are warmer and some are colder. So it's not like you can just stick a thermometer in somewhere and say, OK, that's the ocean's temperature.

D: Of course not. Scientists take thousands of temperature readings from different parts of the oceans. They use a combination of heat sensitive satellites and thousands of floats that directly measure the temperature of ocean water at various depths. Together, these instruments allow scientists to calculate an average ocean temperature.

Y: It's an ongoing process, and scientists are always trying to get more accurate measurements. But they've found that the oceans have in fact been warming at a rate that corresponds with how much heat scientists think has been trapped by greenhouse gasses.

D: Now, this may not sound too bad...as long as the oceans are absorbing most of the extra heat, why worry? But higher ocean temperatures cause icebergs and ice shelves to melt, which raises sea level. And warmer oceans could affect weather patterns in ways that scientists don't fully understand.

Y: So warming of the oceans affects us a

Sundown Above Sea Horizon At Sunset. Natural Sunrise Sky Warm Colors Over Ocean

(Image by Adobe Stock)

How do scientists take the earth's temperature?

Most of the excess heat trapped by greenhouse gasses like carbon dioxide ends up in the oceans. That's because the earth's oceans are kind of like a giant sponge that can hold a lot of heat for a long time.

Now, the oceans are huge. They cover most of the planet. Some parts of the oceans are warmer and some are colder. So it's not like you can just stick a thermometer in somewhere and say, OK, that's the ocean's temperature.

Scientists take thousands of temperature readings from different parts of the oceans. They use a combination of heat sensitive satellites and thousands of floats that directly measure the temperature of ocean water at various depths. Together, these instruments allow scientists to calculate an average ocean temperature.

It's an ongoing process, and scientists are always trying to get more accurate measurements. But they've found that the oceans have in fact been warming at a rate that corresponds with how much heat scientists think has been trapped by greenhouse gasses.

Now, this may not sound too bad, as long as the oceans are absorbing most of the extra heat, why worry? But higher ocean temperatures cause icebergs and ice shelves to melt, which raises sea level. And warmer oceans could affect weather patterns in ways that scientists don't yet fully understand.

Learn more

Source

Earth’s Big Heat Bucket, Nasa Earth Observatory