Global Human Fingerprints on Daily Temperatures in 2023

2023 was a record-breaking year for heat all around the world. Extremely high temperatures were seen across the Americas, Europe, South and East Asia, and Africa, and sometimes persisted for days, weeks, or months. The evident worldwide increasing rate and intensity of heat events begs the question: To what extent is human-caused climate change to blame for these dangerous daily temperatures? It is now possible to quantitatively and confidently attribute human influences on individual heat events soon after occurrence. The World Weather Attribution Initiative (WWA), has pioneered rapid attribution approaches, and regularly releases detailed attribution reports of specific events using state-of-the-art methods. These provide a reliable set of published and self-consistent resources that inform which of the observed 2023 heat events were potentially most noteworthy or impactful. But these studies may also take days-to-weeks to produce, requiring significant investments of time and resources, which limits the opportunities of attributable events that can be assessed over a given year. A new automated attribution system (Gilford et al. 2022) has been developed to complement these reports. It applies techniques similar to WWA to attribute heat events to climate change, and notably, it extends the approach to evaluate temperatures every day, everywhere. In this study we apply the system to develop a hindcast of daily attribution estimates for globally-resolved air temperatures in 2023. We evaluate our system by comparing with WWA reports for several events, including a short-lived event in western Europe (late April 2023) and longer lived events in Southeast Asia (April 2023) and North America (July 2023). Using these as a benchmark, we demonstrate the scale and scope of similarly attributable events around the world in 2023. Results show that the attribution framework produces estimates consistent with in-depth WWA reports. We also show similarly-extreme events were regularly attributable around the world in 2023.