Most of the rain in the Iberian Peninsula falls in winter as moist low pressure systems blow in from the Atlantic. But a high pressure system off the coast, called the Azores high, can block wet weather fronts. The researchers found that winters with “extraordinarily large” Azores highs have increased dramatically from one winter in 10 before 1850 to one in four since 1980. These extremes also push wet weather northward, making it more likely rainfall in northern UK and Scandinavia. Scientists said the more frequent highs in the Azores 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 really unprecedented when you look at the previous 1,000 years,” said Dr Caroline Ummenhofer, at the Woods Hole Oceanographic Institution in the US and a member of the research team. “This has big implications because an extremely high height in the Azores means relatively dry conditions for the Iberian Peninsula and the Mediterranean,” he said. “We could also definitively link this increase to anthropogenic emissions.” The Iberian Peninsula has been hit by increasing heatwaves and droughts in recent years and this year May was the hottest on record in Spain. Forest fires that killed dozens of people in the region in 2017 followed a heat wave made 10 times more likely by the climate crisis, while the Tagus River, the region’s largest, is at risk of drying up completely, environmentalists say. graphic The new research, published in the journal Nature Geoscience, analyzed weather data stretching back to 1850 and computer models that reproduce the climate since AD850. He found that, before 1850 and the start of significant human greenhouse gas emissions, extremely high highs in the Azores occurred once every 10 years on average. From 1850 to 1980, the frequency was once every seven years, but after 1980 it increased to every four years. The data showed that the extremely high altitudes of the Azores reduce the average monthly winter rainfall by about a third. Further data from the chemical analysis of stalagmites in caves in Portugal show that the low rainfall is closely correlated with the high altitudes of the Azores. Computer simulations of the past millennium’s climate cover a period up to 2005. But other studies covering subsequent years are consistent with new findings, and the Azores high is expected to continue to expand, further increasing drought on the Iberian Peninsula, until global carbon emissions are reduced to net zero. Subscribe to First Edition, our free daily newsletter – every morning at 7am. BST “[Our findings] have large implications for 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 overseas tourists in 2019, hosting 84 million visitors. Spain is also the largest producer of olives in the world and an important source of grapes, oranges, tomatoes and other products. But rainfall has been falling by 5-10mm a year since 1950, with a further 10-20% drop in winter rainfall expected by the end of the century. Other research has predicted a 30% drop in olive production in southern Spain by 2100 and a 25% to 99% drop in wine-growing areas across the Iberian Peninsula by 2050 due to severe water shortages. Research in 2021 also linked the Azores high with the summer monsoon in India.
