MercoPress. South Atlantic News Agency

Patagonia increasingly warm.

Patagonia is undergoing the strongest warming process ever in the last four hundred years according to a report jointly elaborated by Argentine and Chilean scientists, and published in the latest edition of the Dutch magazine, Climatic Change.

The report, "Long term climatic changes in the Southern Andes: variations in the XX century in the context of the last 400 years" consists in the reconstruction of temperature patterns in north and south Patagonia since 1640 based on the growth rings of autochthonous trees particularly the Nothofagus Pumilio, locally known as lenga, which grow from northern Neuquén to Tierra del Fuego.

"Never before in the last four centuries have temperatures along the Southern Andes reached the current warming levels", said Ricardo Villalba an Argentine forestry expert with PhDs from the University of Colorado and Columbia University.

The report that is part of the Patagon-1000 project financed by Argentina's Scientific Research and Promotion Agency indicates that Patagonia's gradual warming has been most intense beginning in the mid 1970's with 1998, the "warmest in 400 years".

"We want to characterize the climatic variability in Argentina taking advantage of different vegetation evidence", explains Dr. Villalba.

Climatic records in Argentina and Chile only date back to a century and mostly concentrated in major cities where climatic signals suffer alterations because of urban warming.

Patagonia on the other hand is sparsely populated and has unique mountain ranges, glaciers and vegetation in an area that has hardly suffered human activity intrusion.

"The trees offer us continuous and precise information that normally extends for centuries, and even millenniums", said Dr. Villalba adding that Patagonia has abundant "400/500 years' old lengas and some larch trees from before Christ's time".

"Each year generates a new growth ring, maybe one, two millimetres wide, clearly indicating prevailing climatic conditions: if the summer was cold, the ring is thinner and vice versa".

Argentine scientists extract five millimetre samples of tree trunks hearts with invaluable climatic and historic information from the successive rings, and "since they grow in cold weather these trees are particularly sensitive to temperature changes".

Dr. Villalba said that the report includes research from locations with groups of thirty trees all along the Andes mountain range and "we're now working with 3,700 samples".

Another area or research is charting the Patagonia ice mass and its constant retraction at different speeds.

Primary information from the Argentine Glaciology Department indicates that the Frías glacier in the Nahuel Huapí Park Tronador peak reached its maximum expansion during the last 2,000 years between 1640 and 1660. Since then and until 1850 it retracted at an annual rate of 2,5 metres. However between 1850 and 1890 it jumped to seven metres; between 1910 and 1940, 10 metres and 36 metres from 1976 to 1986.

"Our camp work is showing that the contraction speed since 1986 has actually increased, in all Patagonian glaciers and this is proving consistent with temperature reconstruction", highlighted Dr. Villalba.