Climate Change Impacts On Evapotranspiration in Brazil: a Multi-model Assessment

Abstract A large part of Brazil is highly vulnerable to climate changes projected for the end of the 21st century. Analyzing these vulnerabilities is particularly important for agriculture, since the country is one of the largest agricultural commodity producers in the world. Changes in the reference evapotranspiration (ETo) can impact crops and make cultivation unfeasible. However, studies on ETo patterns under climate change scenarios for Brazil have been restricted to regional scales and use too few climate models or too simplified water balance models for their analysis. This can lead to uncertainties in assessing the impacts of climate change on ETo. Therefore, this study seeks to analyze ETo patterns in Brazil towards the end of the 21st century using two methods that are better at estimating regional ETo, i.e., the Turc and Abtew methods, under two radiative forcing scenarios (RCPs 4.5 and 8.5). Daily data on near surface air temperature (mean and maximum), global solar radiation, and near surface relative humidity from six General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5) were used to analyze the simulations and projections for climate change. The performance of climate simulations is heterogeneous among the GCMs, with overestimations (~ 2.5 mm day-1) in some models, and underestimations (~ 1.5 mm day-1) in others. In general, climate change projections indicate increases of up to 1 mm day-1 in ETo, mainly in the North, Northeast, and Center-West regions of Brazil. Both estimation methods showed similar spatial patterns, however the Turc method projected lower intensity changes compared to the Abtew method.