Background
The authors write that the SAMS (South American Monsoon System) "is the most important climatic feature in South America (Kousky, 1988; Horel et al., 1989; Zhou and Lau, 1998; Marengo et al., 2012) and provides water resources for the millions of people living in the continent (e.g., Berbery and Barros, 2002; Grimm, 2011; Jones et al., 2012)." And they thus say that "documenting climate change in South America is necessary to motivate additional studies to further understand potential impacts on environment, societies, and economies."

What was done
"Motivated by the availability of CMIP5 model simulations," Jones and Carvalho say they investigated the following questions: (1) "Are there significant trends in the large-scale characteristics of the SAMS?" And (2) "Do CMIP5 climate models realistically simulate the observed characteristics of the SAMS?"

What was learned
The two researchers report that "some CMIP5 models have significantly improved their representation of the SAMS relative to their CMIP3 versions." However, they also state that "several models have serious deficiencies," including (1) "excessive precipitation over northeast Brazil," (2) "displaced ITCZ [Inter-Tropical Convergence Zone]," (3) "double ITCZ," and (4) "too little precipitation over the eastern Amazon (near the mouth of the Amazon River)."

What it means
Jones and Carvalho say that "the results of this study indicate lack of spatial agreement in the CMIP5 model projections of changes in total wet-season precipitation over South America," and, therefore, they conclude that "how precipitation during the SAMS will change in the coming decades is still an open question," which suggests that within the greater world economy, there is still a demand for climate modelers that can properly project the future status of the SAMS.

References
Berbery, E.H. and Barros, V.R. 2002. The hydrologic cycle of the La Plata basin in South America. Journal of Hydrometeorology 3: 630-645.

Grimm, A.M. 2011. Inter-annual climate variability in South America: Impacts on seasonal precipitation, extreme events, and possible effects of climate change. Stochastic Environmental Research and Risk Assessment 25: 537-554.

Horel, J.D., Hahmann, A.N. and Geisler, J.E. 1989. An investigation of the annual cycle of convective activity over the tropical Americas. Journal of Climate 2: 1388-1403.

Jones, C., Carvalho, L.M.V. and Liebmann, B. 2012. Forecast skill of the South American monsoon system. Journal of Climate 25: 1883-1889.

Kousky, V.E. 1988. Pentad outgoing longwave radiation climatology for the South American sector. Rev. Bras. Meteorology 3: 217-231.

Marengo, J.A., Liebmann, B., Grim, A.M., Misra, V., Silva Dias, P.L., Cavalcante, I.F.A., Carvalho, L.M.V., Berbery, E.H., Ambrissi, T., Vera, C.S., Saulo, A.C., Nogues-Paegle, J., Zipser, E., Seth, A. and Alves, L.M. 2012. Recent developments on the South American monsoon system. International Journal of Climatology 32: 1-21.

Zhou, J.Y. and Lau, K.M. 1998. Does a monsoon climate exist over South America? Journal of Climate 11: 1020-1040.