According to study released Monday, parts of Portugal and Spain are the driest they have been in a thousand years due to an atmospheric high-pressure system caused by climate change, with serious consequences for wine and olive production.
The Azores High, which circulates clockwise across sections of the North Atlantic, has a significant impact on weather and long-term climatic changes in western Europe.
However, according to a new modeling study published in the journal Nature Geoscience, this high-pressure system "has changed dramatically in the past century and that these changes in North Atlantic climate are unprecedented within the past millennium".
Using climate model simulations spanning the previous 1,200 years, the researchers discovered that this high-pressure system began to expand to encompass a larger region approximately 200 years ago, as human greenhouse gas emissions increased.
It grew much more rapidly in the twentieth century as a result of global warming.
The authors then examined evidence of rainfall levels retained in Portuguese stalagmites spanning hundreds of years and discovered that as the Azores High developed, winters in the western Mediterranean became drier.
The report cites forecasts that precipitation levels might decline by another 10 to 20% by the end of the century, making Iberian agriculture "some of the most vulnerable in Europe".
They warn that as greenhouse gas levels grow, the Azores High will continue to spread, increasing the risk of drought on the Iberian Peninsula and endangering critical crops.
"Our findings have important implications for projected changes in western Mediterranean hydroclimate throughout the twenty-first century," the scientists said.
Wither vines
According to the study, the Azores High works as a "gatekeeper" for rainfall entering Europe, with dry air descending in the summer months to generate hot, arid conditions throughout most of Portugal, Spain, and the western Mediterranean.
During the cooler, wetter winter months, the high-pressure system expands, causing westerly winds to transport rain inland.
This winter rain is "vital" for the region's ecological and economic health, but it has been declining, notably in the second half of the twentieth century.
While prior studies had not been able to separate the impacts of natural variability on the Azores High, the authors claim that their data suggest that its extension over the industrial age is connected to the rise in atmospheric greenhouse gas concentrations.
According to a study mentioned in the newest research, due to severe water constraints, the area suitable for grape production in the Iberian Peninsula might diminish by at least a quarter and could vanish nearly all by 2050.
Meanwhile, studies forecast a 30% decrease in olive production in southern Spain by 2100.
Winemakers are already experimenting with heat-tolerant cultivars and shifting vineyards to higher altitudes to adapt to the changing environment.
Last year, scientists discovered that climate change made a severe spring frost that damaged grape vines in France more likely, with the plants budding sooner and therefore more vulnerable to harm.
