Research highlights “severe implications for both food production and tourism”
Effects of human-caused global heating are blocking vital winter rains, with severe implications for farming and tourism.
This is the message emerging from research published in the online journal Nature Geoscience and cited by the UK’s Guardian newspaper, the Iberian Peninsula is suffering its “driest climate for at least 1,200 years”.
Most of the rain on this landmass falls in winter as wet, low-pressure systems blow in from the Atlantic. But a high-pressure system off the coast – called the Azores high – can block the wet weather fronts.
“The researchers found that winters featuring “extremely large” Azores highs have increased dramatically from one winter in 10 before 1850 to one in four since 1980. These extremes also push the wet weather northwards, making downpours in the northern UK and Scandinavia more likely.
“The scientists said the more frequent large 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 really unprecedented when you look at the previous 1,000 years,” said Dr Caroline Ummenhofer, at Woods Hole Oceanographic Institution in the US, and part of the research team.
“That has big implications because an extremely large Azores high means relatively dry conditions for the Iberian peninsula and the Mediterranean (…) We could also conclusively link this increase to anthropogenic emissions.”
The Iberian peninsula has been hit by increasing heatwaves and droughts in recent years, the Guardian’s article continues. This year May was the hottest on record in Spain, while Portugal is bracing for a new heatwave this week, and is already experiencing the worst drought in living memory.
“Forest fires that killed dozens of people in (Portugal) in 2017 followed a heatwave made 10 times more likely by the climate crisis”, explain environmentalists – while the Tejo River, the longest in the region running into Portugal from Spain, is at risk of “drying up completely”.
This latest research analysed weather data stretching back to 1850 and computer models replicating the climate back to AD850, says the paper. “It found that, before 1850 and the start of significant human greenhouse gas emissions, extremely large Azores highs occurred once every 10 years on average.
“From 1850 to 1980, the frequency was once every seven years, but after 1980 this rose to every four years. Data showed that extremely large Azores highs slash average monthly rainfall in winter by about a third. Further data from chemical analysis of stalagmites in caves in Portugal show that low rainfall correlates closely with large Azores highs.
“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 findings and the Azores high is expected to continue to expand, further increasing drought on the Iberian peninsula, until global carbon emissions are cut to net zero.
According to Dr Ummenhofer, the team’s findings “have big implications for the water resources that are available for agriculture and other water intensive industries or for tourism (…) It doesn’t bode well”, she said pointing to the many millions of summer visitors that flood into Spain and Portugal every year.
The Guardian’s article also pointed to declining harvests in southern Spain, and a projected fall in grape-growing regions across the Iberian peninsula of 25% to 99% by 2050 due to severe water shortages.
Nothing was said about the added demand on underground water sources created by the Portuguese government’s recent policy of green-lighting huge swathes of previously ‘dry orchard land’ for water intensive monocultures.