Matthew's desk

Fifty-six million years ago, CO2 spiked and the planet warmed several degrees within a few thousand years. That was the PETM, the best deep-time record we have of a fast-warming world.

New modeling from Xishuangbanna Tropical Botanical Garden (Communications Earth & Environment) ran the land carbon cycle through that event. Under moderate warming, the land still leaked carbon: a net 66 billion tons. Cross a threshold, and it stopped being a leak. Vegetation and soil collapsed together, losing up to 900 billion tons. The land flipped from sink to source.

We're injecting carbon roughly ten times faster than the PETM did. And we keep betting that forests will store our emissions. The hottest year on record is 2024. The Amazon dried. Canada burned. The bet stands anyway.

Deep time already ran this experiment. The forests lost that round. We're betting on them anyway.

Source: XTBG/CAS, Communications Earth & Environment, May 2026.

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