Anthropogenic influence on summer precipitation trends over South America in CMIP5 models

Abstract

Austral summer rainfall trends are analysed over South America from observations and simulations of the Coupled Model Intercomparison Project version 5 between 1902 and 2005. Positive trends in southeastern South America (SESA) and negative ones in the southern Andes (SAn) are the most significant observed features. Mean trends obtained from an ensemble of 59 simulations from 14 models for the historical experiment (including both natural and anthropogenic forcings) are able to reproduce those precipitation changes, although weaker than observed. Most of the simulations reproduce the right sign of the precipitation changes at both regions. However, associated uncertainty ranges (due to both inter-model dispersion and internal climate variability) are still large. Mean trends for the historical experiment are statistically distinguishable from those obtained for the natural-forcing-only experiment, which exhibit negligible mean values at both regions. Results allow concluding that the anthropogenic forcing has at least a partial contribution in explaining the precipitation changes observed in both SESA and SAn regions during the last century.

Austral summer precipitation interannual variability and trends over Southeastern South America in CMIP5 models

“…The pattern is very similar to that obtained by Vera and Díaz () for a set of 14 CMIP5 models. However, as those authors pointed out, simulated trends are weaker and located westward than those obtained using GPCC data (Figure of Vera and Díaz, ). The associated inter‐model dispersion (Figure (b)) is larger at the tropics.…”

“…The rainfall linear trend resulted from the MEM_A (Figure (a)) exhibits significant values extended over central‐northern Argentina, southern Brazil and Uruguay. The pattern is very similar to that obtained by Vera and Díaz () for a set of 14 CMIP5 models. However, as those authors pointed out, simulated trends are weaker and located westward than those obtained using GPCC data (Figure of Vera and Díaz, ).…”

“…Zak et al ., ; Barros et al ., ) there are very few studies trying to identify the physical mechanisms explaining why a positive rainfall trend is observed in the present climate. Recently, Vera and Díaz () showed that the anthropogenic forcing, associated with the global greenhouse gas emission increase, has at least a partial contribution in explaining the precipitation changes observed in SESA during the last century. On the other hand, Junquas et al .…”

Evaluation of CMIP5 retrospective simulations of temperature and precipitation in northeastern Argentina

“…The seven individual models do present a trend, but it is smaller than that in the observations. As mention above, most of the historical simulations of the CMIP5 models can recognize the right sign of the summer precipitation changes in southeastern South America, although weaker than observed (Vera and Díaz, ). Our results suggest that the annual and summer mean trend in precipitation are weakly simulated also in the northeast region of Argentina.…”

A complete hydro-climate model chain to investigate the influence of sea surface temperature on recent hydroclimatic variability in subtropical South America (Laguna Mar Chiquita, Argentina)

“…However, they concluded that it was difficult to draw a connection between those signatures and the ENSO signal. More recently, Vera and Díaz (2014) used CMIP5 simulations to provide significant evidence that precipitation changes observed in SESA over the last century are at least partially explained by the human-induced greenhouse gases increment. Conclusions from these studies point the need for further investigations to discern whether 20th century hydroclimatic changes in SESA are influenced by forcing from SST anomalies and/or from anthropogenic forcing (i.e., human-induced climate change).…”