CMIP6 Historical Evaluation and Future Changes of Climate Extreme Indices at Regional Scale From the US ‐Mexico Border Region to Central America

ABSTRACT

This study evaluates seven climate extreme indices (CEIs) of precipitation and temperature and assesses their potential changes in 15 regions of the CORDEX‐CAM domain (from the southwestern United States to Central America) for different periods: historical (1981–2010), 2021–2040, 2041–2060 and 2080–2099. We used CHIRTS/CHIRPS and ERA5 reanalysis as references for analysing the CEIs and the historical performance of 17 Global Climate Models (GCMs) of the 6th phase of the Coupled Model Intercomparison Project (CMIP6). Future changes of the CEIs were examined under two Shared Socioeconomic Pathways (SSP: SSP2‐4.5 and SSP3‐7.0). The historical evaluation shows that a multi‐model ensemble (EnsGCMs) using the top 10 GCMs ranks second after the EC‐Earth3 model and the top 10 models are the same with the two references. The EnsGCMs reproduces the observed spatial patterns and the sign of the trends of the CEIs (positive for temperature and negative for precipitation in most regions), with some biases, especially extreme rainfall (R10mm and R95p). Interannual variation of precipitation indices is underestimated. By 2080–2099, TXx is projected to rise 3°C–4°C under SSP2‐4.5 and 4°C–6°C under SSP3‐7.0; TNn shows similar patterns, while DTR changes are small. The contribution of extreme precipitation above the 95th percentile (R95p) could increase between 10% to 30% in the far future (2080–2099), especially in subtropical regions amid a large uncertainty, while precipitation could decrease in tropical regions. This is the first study that analyzes future changes of CEIs using CMIP6 at regional scale in Mexico and Central America; it evidences the need for more regional climate information.