Wednesday, 12 August 2015

Climate Change is Affecting Sherry

This is a worrying article by JA Cañas published in today's La Voz Digital Cádiz:

It is not just another heatwave, it is the confirmation of a trend. It is not just an alarmist assertion, it is a reality proved by various indicators. One of them is also one of the province’s greatest sources of wealth: wine. The bodegas are worried that climate change is causing important changes in the wine which can only be combated with research and the application of new technology.

Carmelo García knows all about it. He is a professor at the University of Cádiz (UCA) and in charge of the Centro Andaluz de Investigaciones Vitivinícolas (CAIV)run by the university in conjunction with the Junta. He has spent many years researching how to save the grapes from the grave problem of rising temperatures. The key is in the vegetative cycle of the grape and its ripening during the summer. High temperatures make the grape ripen more quickly and with a higher sugar content which will ferment out to a higher level of alcohol. This happens with all grape varieties and is forcing bodegas to pick the grapes sooner, like in mid-August.

Harvesting ever earlier (foto:lavozdigital)

You might think that would solve the problem – but for one other factor. As it ripens, the grape converts its acids into sugar, but the aromas also appear. The high temperatures are knocking off balance the development of sugars and aromas. While the sugar content rises rapidly it is not so with the aromas, so earlier picking brings in grapes with less aroma. At least it could be worse for the Sherry trade as they use mainly Palomino which is not the most aromatic of grapes, its aromas develop during ageing.

Sherry is, of course, not the only wine produced in the province. Many table wines are produced from other grape varieties and here aroma is more important. Red grapes present a particular problem as the heat causes the sugars to rise quickly but not the aromas or the colour. Once grapes were picked when they had enough sugar to achieve the intended alcohol level, but now they are picked according to phenolic ripeness as well, that is properly ripe, not just plenty of sugar. If you pick the red grape on say the 20th August it will already have enough sugar, but very little colour. If you wait longer you will get the colour but the wine will be far too strong. Worse still, the market currently prefers wines with less alcohol.

After years of research, the CAIV knows the climate is against us. Climate change is already obvious and harvests are regularly much earlier than say 30-40 years ago. Furthermore, the CAIV works with predictive models which show that some regions will have serious problems making wine at all in the future, and that the whole of Spain will be affected.

Research is therefore focusing on the grape, its vinification and the wine. They are studying irrigation and the possibility of nutrient supply to compensate for the fast ripening. They are also looking into old grape varieties which are perfectly adapted to vineyards in the province with higher temperatures with the idea of cloning them and planting them more widely. As to winemaking, they are looking into the maceration of the grape skins to extract more colour and aroma. The last option is to reduce the alcohol level of the wine without the loss of aroma; the centre already has a machine which removes alcohol. It is hoped to have all the necessary results in the next three years as they are well aware that this is neither trivial nor an exaggeration, it is a serious and worrying reality and clear results are needed to deal with it.

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