What was done
From a regional inventory of monthly droughts for the portion of South America located south of approximately 22°S latitude -- which was divided into six sections (the central region of Chile plus five sections making up most of Argentina) -- the authors evaluated the annual occurrence of droughts and their persistence in what they describe as "an attempt to determine any aspects of the impact of global warming."

What was learned
In the words of Minetti et al., "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.

What it means
All things considered, it would appear that 20th-century global warming has not promoted an increase in droughts over the southern third of South America.