In 2024, the Amazon region experienced severe wildfires driven by exceptional drought conditions. Advanced fire emission models estimated Amazon carbon monoxide (CO) emissions between 28 and 62 Tg during the main August-September Amazon fire season. The majority of the 2024 CO emissions came from (understorey) forest fires, unlike the previous 6 years for which deforestation fires were the dominant CO source. The strong sensitivity of forest fires to climate makes them the dominant source of inter-annual variability, and 2024 Amazon forest fire emissions were approximately four times the 2018–2023 average. Comparison with Sentinel-5p observed atmospheric CO columns indicates nevertheless that even advanced fire emission models underestimate CO emissions by a factor of 1.5–3. This is likely due to prolonged smouldering of fires that enhance fuel consumption during droughts. These results provide strong indications that Amazon 2024 wildfire carbon emissions are also underestimated in advanced fire emission models.