How Bad Was 2023's Heat? Tree Ring Data From Ponderosa Pine Bigelow 224 Show Us

Deep in the Sonoran Desert, high on a mountain’s wind-swept peak, there lives a tree known as Bigelow 224. With its stout orange trunk and long, graceful needles, the tree looks like any other ponderosa pine growing on Mount Bigelow. But a sliver of its wood, taken amid Earth’s warmest year on record, shows that this tree has a story to tell — and a warning to offer.

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But then came 2023, the hottest year that humanity — and Bigelow 224 — had ever seen. All around the planet, temperature records fell like dominoes. Up on Mount Bigelow, an unrelenting heat wave made the air feel like an oven and sucked moisture from the thin soil. The toll of those unprecedented conditions was etched into Bigelow 224’s trunk. Scorched by relentless heat and parched by a delayed monsoon, it appeared to stop growing midway through the season. The ring for this year is barely a dozen cells wide. It is a silent distress signal sent by one of Earth’s most enduring organisms. A warning written in wood.

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For example, if the early summer weather became too hot and dry, the trees would close the pores on their needles through which they admitted air for photosynthesis. They became less choosy about the carbon they consumed — opting to use a heavier, less nutritious form of the element that was already available in their tissue, rather than risk losing moisture through open pores. Put simply, Morino said, the trees starved themselves to avoid dying of thirst. Meanwhile, cell production slowed down, and the cells themselves were made smaller. The emerging wood looked dark and dense, almost like the latewood that usually appeared later in the year.

This, Morino’s research showed, is what created the false rings seen in so many southwestern tree cores. The arrival of the summer monsoon usually allowed the trees to resume regular cell production for a few more months. But the thin lines of drought-formed cells remained in the wood — the signatures of a species acutely adapted to its environment, permanent evidence of the trees’ commitment to careful growth. “In some ways, that sensitivity really helps them,” Morino said. “The trees are sensing it’s getting drier and warmer and slowing down cell production and waiting for summer rains … versus kind of going gung-ho and using up all your resources, and then you’re screwed.”

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https://www.washingtonpost.com/climate-environment/interactive/2023/global-heat-record-arizona-trees-rings/?itid=sf_climate_climate_top-table_p001_f003