Résumé
The IPCC reported that the 2011–2020 decade has been the warmest on record worldwide. The frequency of climate extremes has increased and the future rates of warming will be well above historical averages. Climate warming has already modified species seasonal activity with cascading effects on species interactions, geographical ranges, ecosystems productivity and feedback to the atmosphere. However, we lack information on how the new climate regime will translate in terms of impacts for human populations and ecosystems. Here we report on abnormal seasonal activities of plants and animals, which took place in Europe and other countries worldwide since 2015. We show that they are unpreceded, related to warmer fall and winter as well as drier summer conditions. These anomalies are projected to increase in frequency in a near future and might have dramatic consequences for biodiversity dynamics, ecosystems functioning and human activities.