Assessing the Impact of Climate Change on Water Resources: The Challenge Posed by a Multitude of Options

Abstract

Global warming due to anthropogenic emissions of greenhouse gases is already altering the Earth’s climate. A changing climate implies shifts in long-term temperature and precipitation patterns, which in turn will affect the spatiotemporal distribution of water resources. It is imperative to study the impact of climate change on water resources so that adequate adaptation actions can be planned well in advance. We, therefore, need reliable methods to estimate how the timing and magnitude of available fresh water in a region may change in response to a changing climate. This chapter summarizes the main approaches that are used to achieve this goal. We focus on the numerous choices that a modeler faces when attempting to quantify the impact of climate change on water resources of a region. We discuss the relative strengths and weaknesses of each approach. These choices vary from the choice of model structures representing global climate and local hydrology, possible trajectories of greenhouse gas emissions in the future, to methods for model evaluation. Wherever feasible, we provide recommendations that can help a modeler in choosing an appropriate course of action. We conclude the chapter with a discussion on recent techniques developed to deal with large uncertainties in projections of climate change and possible research directions that will benefit the impact assessment community.