How climate change is impacting the harvest in Rioja?

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Some people still doubt that our planet is getting warmer, but growers and winemakers in Rioja aren’t among them.  In a recent study carried out by sociologists Sergio Andrés Cabello and Joaquín Giró of the University of La Rioja*, 90% of the 481 growers and winemakers surveyed believe that climate change is a reality.  65% feel that its effects will be negative or very negative and 46% think that Rioja will have to adapt to new circumstances.

This study also revealed that between 1950 and 2014, the average temperature in the Rioja region increased between 0,9ºC and 1,2ºC (1,6ºF-2,2ºF). Higher temperatures and lower rainfall have impacted the harvest in Rioja in several ways. First of all, the growth cycle of the grapes takes place earlier in the late summer and fall.  In the future, warmer weather in September and October may not create the high temperature differential between day and night for the grapes to ripen properly.

The Spanish Institute of Meteorology predicts that the Iberian Peninsula will experience severe warming in the 21st century:


Warmer temperatures create problems determining the optimum time to pick because of an imbalance between the sugar/acidity level and the phenolic compounds responsible for color and texture in the finished wine.

To pick when the potential alcohol in the grapes is 12 or 13%, the level of phenolic compounds that produce color and texture is often too low.  On the other hand, waiting until these phenolic compounds are at an optimum level means that the potential alcohol in the grapes can be as high as 15 to 16%.

Fernando Martínez de Toda, chair of the Department of Viticulture at the University of La Rioja suggests several possible ways farmers can mitigate the effects of climate change. Some of these changes delay the ripening of the grapes such as planting new vineyards at higher altitude and prioritizing planting grapes with longer growth cycles such as graciano and garnacha.  Other methods include using clones that ripen later, severely cutting back leaf canopies, late pruning and even forcing a second budbreak.  Some of these methods can be used at little cost to growers but others, such as planting at higher altitude require heavy investment.

How is climate change affecting tempranillo, Rioja’s star varietal? A study of the potential long-term evolution of Rioja vineyards carried out by the Basque Research and Agrarian Development Institute postulated that with a 4ºC increase in temperature, an increase in carbon dioxide and a decrease in relative humidity to 12%, grapes from Rioja vineyards would produce juice with less color (a sign of lower quality according to today’s standards) and an increase in pH, causing the wines to lack crispness and texture.

Tempranillo, a varietal with low acidity that even today leads winemakers to add acid to lower pH, would be especially affected. Because tempranillo’s growth cycle is shorter than other varieties, it would bear the full impact of higher daytime temperatures without benefiting from a cooler nighttime.

In spite of these warnings and the potential investment that may be  required to deal with increasing temperature and less rainfall in Rioja, Fernando Martínez de Toda is optimistic, at least in the short and medium term. He says, “Global warming has been mostly positive for Rioja. In the past, in some parts of our region, grapes were picked just after veraison with only 10 or 11% potential alcohol.  Today warmer temperatures allow grapes at higher altitude and in cooler parts of Rioja to ripen fully.

* “Evaluación del impacto del cambio climático en la producción vitivinícola de la DOCa Rioja”.
Tom Perry, Inside Rioja.