What was done
For nine areas of contrasting environment within the Pampas region of Argentina, which accounts for over 90% of the country's grain production, the authors evaluated changes in climate over the 20th century along with changes in the yields of the region's chief crops (soybean, wheat, maize and sunflower).  Then, after determining upward low-frequency trends in yield due to technological improvements in crop genetics and management techniques plus the aerial fertilization effect of the historical increase in the air's CO2 concentration, these annual yield anomalies and concomitant climatic anomalies were used to develop relations describing the effects of precipitation, temperature and solar radiation on crop yields, so that the effects of long-term changes in these climatic parameters on Argentina agriculture could be determined.

What was learned
Although noting that "technological improvements account for most of the observed changes in crop yields during the second part of the 20th century, which totaled 110% for maize, 56% for wheat and 102% for sunflower, Magrin et al. report that due to changes in climate between the periods 1950-70 and 1970-99, yields increased by 38% in soybean, 18% in maize, 13% in wheat, and 12% in sunflower.

What it means
Twentieth-century climate change, which is claimed by climate alarmists to have been unprecedented over the past two millennia and is often described by them as one of the greatest threats ever to be faced by humanity, has definitely not been a problem for agriculture in Argentina.  In fact, it has helped it.