For decades, climate scientists have been tracking a curious phenomenon. Carbon dioxide levels in the atmosphere are steadily increasing overall but they also rise and fall in an annual rhythm — like the planet is breathing.

Each spring, in the southern hemisphere, carbon dioxide levels start to plateau or maybe even drop slightly before shooting up again after summer.

So what's driving these seasonal changes?

You can binge more episodes of the Lab Notes podcast with science journalist and presenter Belinda Smith on the ABC Listen app (Australia). You'll find episodes on animal behaviour, human health, space exploration and so much more.

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Featuring:

• Nick Deutscher, atmospheric chemist at the University of Wollongong

This episode of Lab Notes was produced on the lands of the Wurundjeri and Menang Noongar people.