Essential Climate Variables for Accurate Climate Change Impact Studies on Hydrological Regime: A Comprehensive Review

Abstract

Essential Climate Variables (ECVs) are a set of key climate variables, identified by the Global Climate Observing System (GCOS) for understanding the climate system. Understanding the interactions between ECVs is critical for accurately modelling and predicting the impacts of climate change. In addition to the direct impacts of changes in ECVs, there are also complex feedback mechanisms that can either amplify or dampen the effects of climate forcings at a larger scale. While many researchers may use slightly different sets ECVs, some significant climate variables that are sometimes neglected, which can lead to underestimating or overestimating the impacts and introduce significant uncertainties in the results. This review paper aims to provide an overview of the climate system, ECVs, climate feedbacks, climate forcings, and methodologies for identifying the significant ECVs for climate change impact studies on hydrological regimes and to understand the uncertainties introduced due to neglecting few ECVs. A comprehensive review was conducted, consisting of an in-depth analysis of approximately 80 relevant scholarly articles. Methodologies for identifying the ECVs are discussed which involve a multi-disciplinary approach that combines empirical analysis, climate model simulations, and ensemble approach. It can be inferred that ECVs that have a significant impact on hydrological regimes, such as groundwater, soil moisture, atmospheric humidity, etc. are often excluded from analysis due to a lack of available spatial and temporal data. In conclusion, improving the availability and accessibility of data for important ECVs is imperative, and can be achieved through investing in new monitoring methods and technologies, enhancing data sharing and collaboration among institutions and researchers, and prioritizing funding for data collection and analysis. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.