A precise ecosystem evapotranspiration (ET) estimate is essential for understanding the complex relationship between plants' energy-water-carbon fluxes. Besides, robust ecosystem ET estimation under different water stresses can provide insight into plants' response to extreme weather and environmental conditions. However, for such very preciseness, we must accept the individual and comprehensive interlinked mechanistic relationships between ecosystem ET and its controlling variables for determining the response of ecosystem ET towards extreme climate events. Due to recent drought events in the European continent since the 2000s, many geographical hotspots are getting attention to understanding the complicated mechanistic relationship between ecosystem ET and its controlling variables under such extreme water stress conditions. Consequently, precise ecosystem ET estimation of the European continent's water-stressed ecosystems, i.e. agriculture, will give insight into the sustainability of Europe's agricultural production to ensure sufficient food for millions of people in future. The recent heatwaves and drought in 2018 impacted ecosystem ET substantially over the European continent, which may be a big concern for the European ecosystems' future water, energy, and CO2 balance. The research outcomes of the first research article (c.f. Ahmed et al., 2021) showed that the European continent had up to 50% reduced ecosystem ET compared to a 10-year reference period due to a combined heatwave and drought event in 2018. The results also showed extreme surface air temperature (Tsa) and precipitation (P) anomalies. Due to such extreme climatic phenomena, agricultural land, mixed natural vegetation, and the European continent's non-irrigated agricultural areas were mainly affected. In conclusion, the first research article explains the importance of modelling precise ecosystem ET in variable time and space. However, modelling and estimating precise ecosystem ET is still challe