According to research, Spain and Portugal are suffering from their driest climate in at least 1,200 years, with severe consequences for both food production and tourism.
Most of the rain on the Iberian Peninsula falls in winter when wet low-pressure systems pour in from the Atlantic. But a high pressure area off the coast, called the Azores High, can block wet weather fronts.
The researchers found that winters with “extremely large” Azores highs have increased dramatically from one winter in 10 before 1850 to one in four since 1980. These extremes are also pushing wet weather north, making downpours more likely in northern Britain and Scandinavia.
The scientists said the more frequent Great Azores Highs could only have been caused by the climate crisis, caused by humanity’s carbon emissions.
“The number of extremely large Azores highs in the last 100 years is truly unprecedented when you look at the last 1,000 years,” said Dr. Caroline Ummenhofer from the Woods Hole Oceanographic Institution in the USA and part of the research team.
“This has major implications because an extremely large Azores high means relatively dry conditions for the Iberian Peninsula and the Mediterranean,” she said. “We could also conclusively link this increase to anthropogenic emissions.”
The Iberian Peninsula has been hit by increasing heat waves and droughts in recent years, and this year May in Spain was the hottest on record. Wildfires that killed dozens of people in the region in 2017 followed a heatwave made 10 times more likely by the climate crisis, while the Tagus River, the longest in the region, is at risk of drying up completely, according to environmentalists.
The new research, published in the journal Nature Geoscience, analyzed weather data dating back to 1850 and computer models recreating the climate up to AD 850. It found that before 1850 and the start of significant human greenhouse gas emissions, extremely high Azores highs occurred on average every 10 years.
From 1850 to 1980 the frequency was once every seven years, but after 1980 this increased to every four years. The data showed that extremely high Azores altitudes reduce the average monthly precipitation in winter by about a third. Further data from chemical analysis of stalagmites in caves in Portugal show that low rainfall correlates closely with high highs in the Azores.
The computer simulations of the climate of the past millennium cover a period up to 2005. But other studies covering later years are consistent with new evidence, and the Azores High is expected to continue to expand and further intensify drought in the Iberian Peninsula until global carbon emissions are reduced to net zero.
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“[Our findings] have major impacts on the water resources available for agriculture and other water-intensive industries or for tourism,” said Ummenhofer. “It doesn’t bode well.” Spain was the second most popular country for foreign tourists in 2019, with 84 million visitors.
Spain is also the world’s largest producer of olives and an important source of grapes, oranges, tomatoes and other produce. But precipitation has fallen by 5–10 mm per year since 1950, and a further 10–20% fall in winter rains is expected by the end of the century.
Other research has projected a 30% decline in olive production in southern Spain by 2100 and a 25% to 99% decline in wine-growing areas in the Iberian Peninsula by 2050 due to severe water shortages. Research in 2021 also linked the Azores High to the summer monsoons in India.