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NEW PREPRINT: You may recall Joshua trees started flowering fully four months early this year. Was that due to climate change? Well, @colincarlson.bsky.social and I called in Chris Callahan to formally test that hypothesis, and the answer is... it probably wasn't! doi.org/10.64898/202...

Working from real weather data, the model correctly predicts flowering in the normal flowering season, Q1 and Q2 for most years (purple areas in the tiny range-maps in this figure); it also correctly predicts documented out-of-season blooms in Q4 of 2018 and 2025!

Chris provided weather data simulated without human-caused climate change, and when we fed that counterfactual weather into the model... it recovered out-of-season blooms in the fourth quarters of 2018 and 2025. Here's just Q4 for each of those years, under factual and counterfactual conditions:

This actually makes sense. The model found Joshua tree flowering is mostly driven by precipitation—the out-of-season flowering events were in years with unusually wet fourth quarters—but in Joshua tree's range climate change has had a much bigger impact on temperature than on average precipitation.