Read here. Using the standard IPCC's Climategate "scientific" methodology, we have concluded that large human CO2 emissions directly cause fewer severe droughts. This must be the case since no other known factor(s) could possibly be responsible for less severe droughts in the southern region of South America. /sarc.
Per the Minetti et al. peer-reviewed study:
"...the presence of long favorable tendencies [1901-2000] regarding precipitations or the inverse of droughts occurrence are confirmed for the eastern Andes Mountains in Argentina with its five sub-regions (Northwest Argentina, Northeast Argentina, Humid Pampa, West-Centre Provinces and Patagonia) and the inverse over the central region of Chile." From the middle of 2003 to 2009, however, they report "an upward trend in the occurrence of droughts with a slight moderation over the year 2006." Last of all, they note that the driest single year periods were 1910-11, 1915-16, 1916-17, 1924-25 and 1933-34." [J. L. Minetti, W. M. Vargas, A. G. Poblete, L. R. de la Zerda and L. R. Acuña 2010: Theoretical and Applied Climatology]