The Iberian Peninsula is currently experiencing its worst drought in 1200 years and the cause is almost certainly climate change. This is now reported by a working group led by Caroline C. Ummenhofer from the Woods Hole Oceanographic Institution using observation data and climate models. As the team reports in the journal Nature Geoscience, the persistent lack of rain is due to the Azores High, a persistent high-pressure zone over the North Atlantic that is heavily influencing the weather in Europe. In the last 250 years, this has been increasingly large in winter, thereby diverting the winter rains away from Spain and Portugal.
The Azores High is one of the factors that control the trajectory of low-pressure systems over the North Atlantic. In summer its center is more near Bermuda, in winter it is more in the western Atlantic near the Azores. Under normal conditions, the winter lows that supply most of the water to Spain and Portugal can pass north of this high-pressure core to the Iberian Peninsula. On the other hand, if the high is particularly large, it diverts the rainfall to northern Europe and Scandinavia. According to the models, an oversized Azores high will reduce precipitation by about a third.
In fact, stalactite data from caves show that such years are unusually dry in the region. The team’s analyzes and climate simulations suggest that this is happening more and more often over the past 250 years. The models suggest that a comparable situation has not existed for at least 1200 years – if not longer. Before 1850, i.e. during the Holocene climate, which was largely unaffected by humans, such oversized Azores highs occurred about once every ten years. In the century that followed, it was every seven years, and since 1980 every four years.
The original of this article “Worst drought in 1200 years in Spain and Portugal: Climate change probably to blame” comes from Spektrum.de.
