In the Peruvian Andes, climate variability impacts small-scale farmers that rely on rain-fed agriculture. With progressing global warming, there is a pressing need for information on potential future climatic changes that would help to develop adaptation strategies for local communities. Climate change projections are particularly uncertain for high-mountain environments as traditional coarse-scale (∼> 100 km) global climate models do not resolve complex topography and associated steep gradients in climate conditions and changes.
The objective of this work is to determine whether and how important climatic features for agriculture in the region will change in the future for an ensemble of regional climate models created within the Coordinated Regional Climate Downscaling Experiment (CORDEX) framework. This ensemble provides regionally downscaled climate projections at ∼ 50 km, allowing for a more realistic representation of the Andes mountain range. In this study, I investigate four regional climate models (RCMs) of CORDEX’s South American domain, that were simulated under the representative concentration pathways 4.5 W m−2 and 8.5 W m−2 . First, I evaluate their performances by comparing a historic baseline period (2006 - 2025) to reference data (2006 - 2020, ERA5 and CHIRPS). I then evaluate expected changes by comparing two future periods (2040 - 2060, 2080 - 2100) of the RCMs’ projections in the wet season (November to March) to the historic period. The study domain is chosen according to the scale of the analysed metric (most of the South American continent or the Peruvian Andes).
In the historic period, I find that all ensemble members except for one are able to reproduce climatic features, like upper-level circulation, seasonal cycle of precipitation and temperature in the target region. By the end of the century, the RCMs predict a significant increase of near-surface air temperature depending on the emission scenario (2 °C - 4.5 °C) and a decrease in frost days for the Peruvian Andes. Large discrepancies are found between the RCMs for mean precipitation and number of extreme precipitation events: while some RCMs predict an increase, others predict a decrease. Furthermore, the Peruvian Andes will face a shift in the upper-level zonal wind to slower easterlies in austral summer throughout the century. I discuss uncertainties in the precipitation data because RCMs cannot capture all processes in complex terrain. I furthermore explore the previously documented relationship between precipitation and upper-level zonal flow, concluding from my findings that it is not linear, neither in the reanalysis nor in the CORDEX data. Based on this analysis, I cannot confirm nor rule out a drying in the Peruvian Andesby the end of the century as was predicted in another study.
This work is an attempt to use CORDEX’s RCMs to provide an overview about the changes residents in the Peruvian Andes will possibly face in the course of the current century.