More on Climate Change

An article by Paz Gutiérrez (EFE Cádiz) in today's Diario de Jerez

One of the unforseen – until recently - consequences of global warming is the accelerated ripening of the grape and the rise in sugar content and consequent alcohol level in the wine. This has forced producers to harvest earlier year after year, even as early as the beginning of August – over a month earlier than the historic norm.

The Centro Andaluz de Investigaciones Vitivinicolas (CAIV), a research institute linked to the University of Cádiz (UCA) and the Junta’s Economy, Innovation and Science Department, has spent three years testing on the ground for solutions to this problem which, beyond early harvest dates has devastating effects on the aroma and colour of a wine.

The more sunshine and heat the grape receives, the more it converts its acids into sugars. Over the last ten to fifteen years global warming has progressively increased the temperature by over five degrees explains Carmelo García, the CAIV director. The problem is less acute with Palomino destined to become Sherry, but it seriously affects grapes for table wines, especially red ones.

Harvested grapes (foto:diariojerez)

He says the accelerated ripening does not run parallel with the development of colour and aroma. In the young fruit the juice just smells vegetal and has not yet acquired the colour nor the aroma which characterise the wine. But if you let the phenolic ripening process take its course you will end up with a wine with 17% alcohol, something unthinkable until now, but which happened three years ago in the Rioja. It is a widespread problem affecting not only many parts of Spain, but also Italy and Portugal.

One of the solutions the CAIV is working on is de-alcoholisation equipment, a technology never before needed but which is giving good results and financed by the EU. This equipment allows you to extract the alcohol without extracting the aroma and colour. They are also working with the bodegas connected with the UCA “Interconecta” programme, bodegas such as Barbadillo, González Byass, Caballero and Manuel Aragón.

From July till September a dozen researchers are dedicated full time to the application of natural treatments to the vineyards, like providing more water or removing certain bunches from the vine, pruning leaves or supplying nutrients. As to the winemaking they are testing skin maceration, not normally used in the making of white wine, keeping the skins in contact with the must by mechanical means.

Given that every vintage is different, it is hoped that in three or four years it should be possible to see which treatment is most effective and economical, and to share the results with other Spanish or European universities who are also looking for solutions. Ideally governments would agree on how to tackle this problem, but in the meantime the search goes on.