Reference
Mundo, I.A., Masiokas, M.H., Villalba, R., Morales, M.S., Neukom, R., Le Quesne, C., Urrutia, R.B. and Lara, A. 2012. Multi-century tree-ring based reconstruction of the Neuquen River streamflow, northern Patagonia, Argentina. Climate of the Past 8: 815-829.
Background
Climate alarmists continue to claim that global warming will lead to more extreme (both high- and low-volume) river flows, characteristic of more extreme drought and flood conditions. However, river flow records in southern South America, according to the authors, "extend for only a few decades, hampering the detection of long-term, decadal to centennial-scale cycles and trends," which are needed in order to ascertain the degree of validity of climate-alarmist claims for that part of the world.
What was done
In an effort designed to greatly extend the streamflow history of Argentina's Neuquen River - which they say is of "great importance for local and national socio-economic activities such as hydroelectric power generation, agriculture and tourism" - Mundo et al. employed 43 new and updated tree-ring chronologies from a network of Araucaria araucana and Austrocedrus chilensis trees in reconstructing the October-June mean streamfow of the river for each year of the 654-year period AD 1346-2000, using a nested principal component regression approach.
What was learned
The eight researchers determined that in terms of the frequency, intensity and duration of droughts and pluvial events, "the 20th century contains some of the driest and wettest annual to decadal-scale events in the last 654 years." However - and it's a very big however - they report that "longer and more severe events were recorded in previous centuries."
What it means
Once again, and for another part of the planet, the climate-alarmist claim that what they call unprecedented global warming will bring unprecedented drought and flooding to almost every nook and cranny of the globe is shown to be, shall we say, not yet apparent? In fact, because the bulk of the 554 years that preceded the 20th century were part of the much colder Little Ice Age, it would appear that, if anything, the "unprecedented" global warming of the past century has brought Argentina's Neuquen River less extreme streamflow conditions, which is just the opposite of what the world's climate alarmists contend should have happened.