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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...

Chris helped us perform what's called an attribution analysis: We used @inaturalist.bsky.social records to train a model of Joshua tree flowering based on seasonal weather, then used the model to project Joshua tree flowering from weather simulated under a scenario without climate change.

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!

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.

This is a preprint, so we'll see what reviewers have to say— but I think it's pretty neat that we're able to answer these kinds of questions, thanks to iNaturalist users and some careful modeling. Read the whole thing and let us know what you think: doi.org/10.64898/202...