Present-day and future climate over central and South America according to CMIP5/CMIP6 models

In tropical regions, particularly in Central and South America (CSA), the projections of climate seasonality under climate change are still uncertain. This is especially true for ecologically-relevant variables such as precipitation and temperature. However, assessments of model-based projections of seasonal climate for this region are scarce. We analyzed the simulation of seasonal precipitation and air surface temperature in CSA and six sub-regions within from 49 models included in the Coupled Intercomparison Project Phase 5 (CMIP5) and 33 models from CMIP6. In general, continental patterns and seasonality of both variables are moderately well resembled, while most models show systematic biases over the oceans, producing unrealistic spatial patterns. To quantify how well CMIP5/CMIP6 models simulate these variables, we used Taylor diagrams with respect to TRMM for precipitation and ERA5 for temperature. Precipitation shows the largest spread among models. Conversely, temperature shows a better simulation. CMIP5/CMIP6 models exhibit a better performance simulating both variables during December-January-February and March-April-May than during the other seasons. This is partly due to the reduced model biases in representing the Intertropical Convergence Zone during these two seasons. In general, biases are reduced in the CMIP6 models with respect to CMIP5. Regarding regional evaluations, precipitation patterns for Mesoamerica, Cerrado and Chaco regions are better reproduced compared to TRMM, while the annual cycles for the Andes hotspot, Central Chile and Guianas are not well simulated, mainly during their wet seasons. However, these biases are reduced in CMIP6 models. In regard to precipitation projections, models only agree over most of the regions with decreasing precipitation. Conversely, temperature exhibits a general consensus on persistent warming even during the historical period, with an average increase of 6 degrees C by the end of the century, according to the CMIP6 models.

Automated summary

In tropical regions, particularly in Central and South America, climate seasonality projections under climate change remain uncertain. Models show moderately accurate simulations of precipitation and temperature on the continents but exhibit systematic biases over oceans, with better performance during certain seasons. Despite some improvements in CMIP6 models, biases still exist in simulating regional precipitation patterns and annual cycles. Projections suggest decreasing precipitation in most regions, while there is a general consensus on persistent warming for temperature, with an average increase of 6 degrees Celsius by the end of the century according to CMIP6 models.