Effects on the hydrological cycle and the availability of water resources are among the most important potential impacts of human-induced climate change. However, previous assessments of observed warming-induced changes in dryness are influenced by natural climate variability and show conflicting results due to uncertainties in the response of evapotranspiration. Here we employ novel observation-based water availability reconstructions from data-driven and land surface models from 1902 to 2014; a period during which our planet has experienced global warming of approximately 1°C. The analysis reveals consistent changes in average water availability of the driest month of the year in the recent three decades compared to the first half of the 20th century. The global pattern of changes is extremely likely influenced by human-induced climate change as it is consistent with climate model estimates that account for anthropogenic effects and it is not expected from natural climate variability. There is regional evidence of drier dry seasons predominantly in extratropical latitudes and including Europe, Western North America, Northern Asia, Southern South America, Australia, and Eastern Africa. The intensification of the dry season is generally a consequence of increasing evapotranspiration rather than decreasing precipitation.