The Climatic Energy Balance Diagram (CEBD) highlights changes in the hydrological cycle of the Danube River basin

Abstract Abstract: The impacts of global warming are the subject of intense research. However, it is difficult to agree on ways to prevent and mitigate adverse changes until the root causes of the problem can be formulated in simple and understandable terms. The aim of this study is to highlight changes in the hydrological cycle using a new graphical method, the Climatic Energy Balance Diagram (CEBD), or climate diagram for short. The key terms of the energy balance equation determine the annual operating points or working points of the climatic energy distribution process. The easy-to-use visualization tool promotes evaporative fraction (EF) as a key metrics, expressing the efficiency of the climatic energy distribution process. Analysis has shown that keeping it at around 0.7 in the Danube basin requires increased evaporation. The 30-year average value of evaporation has increased by 29 mm (from 482 mm to 507 mm) while that of sensible heat by 23 mm (from 196 mm to 219 mm) between 1961–1990 and 1991–2020, both expressed in water-depth equivalents. A normalised version of the CEBD can be used to compare areas in different climatic conditions. The diagram highlights the key role of water and evaporation in the process of distributing climatic energy to ensure environmental sustainability and can facilitate better communications between different research areas and stakeholders (farmers, regulators, investors, policy makers) while maintaining a multidisciplinary approach.