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Trains, now on Uber. T's and C's apply. Check the Uber app. This is Scientific American 60 Second Science.

I'm Julia Rosen.

To us humans, climate change feels like something that's happening to the atmosphere, but most of the action is actually at sea.

About 90% of the heat that gets trapped by greenhouse gases is absorbed by the ocean.

So it's really important to track that energy in the climate system

and track the warming off the ocean.

Juren Kalis, an oceanographer at Caltech.

Of course, the ocean is really big and taking its temperature is hard.

satellites give information about the surface and scientists have launched drifting devices

that measure conditions in the upper mile of water, but researchers still struggle to collect that measures

still struggle to collect data from the deep ocean and to detect the long-term

trends underlying day-to-day variations in temperature. Now, however, scientists have developed a new technique

that allows them to measure temperature changes across entire ocean basins. The idea dates back to the 1970s

when researchers first proposed using sound waves to study

ocean warming because the speed of sound through water depends on the physical

properties of that water which are related to temperature.

And roughly if we warm up. that water, which are related to temperature.

And roughly, if we warm up the ocean temperature by one degree,

the sun speed change.

It would be four meters per second. And this is a very sensitive change.

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