Fish traverse the underwater tunnel in 2024 at the Aquarium of the Bay in San Francisco. Visiting an aquarium can connect the dots for the causes of climate change.

At Aquarium of the Bay, the most important moments are often quiet ones.

A child stands in the tunnel beneath San Francisco Bay and looks up as a leopard shark passes overhead. A parent reaches into a touch pool and feels the wing of a bat ray. For a few seconds, the bay stops being scenery — something glimpsed from a ferry, a bridge or a restaurant window — and becomes alive. Close. Present.

That is why the recent news about ocean heat feels so urgent to me. The ocean’s crisis is easy to miss because it can look, from shore, like nothing at all. No flames. No smoke. A bright, sunny day where land meets the bay. Sea lions barking at Pier 39. 

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But beneath the water’s familiar surface, the long memory of the climate is changing.

For decades, the ocean has absorbed more than 90% of the excess heat trapped by greenhouse gases. It has been the buffer between us and the full force of what we have done to the atmosphere. Our oceans have kept absorbing the heat we’ve fed them, keeping it like a secret. Because the bill was hidden beneath the surface, most of us never had to look at it.

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This year, it has started giving that secret up.

Last month was the warmest June ever recorded for the global ocean, with an average sea surface temperature of........

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