Ancient Spanish trees reveal Mediterranean storms are intensifying
Ancient pine trees growing in the Iberian mountains of eastern Spain have quietly recorded more than five centuries of Mediterranean weather. Now, by reading the annual growth rings preserved in their wood, scientists have uncovered a striking message: today's storms and droughts are becoming more intense and more frequent than almost anything the region has experienced since the early 1500s.
New research, published in Climate of the Past, reconstructs 520 years of rainfall variability in the western Mediterranean using tree-ring data from long-lived Spanish pines (Pinus sylvestris and Pinus nigra). The findings show that recent decades stand out sharply in the historical record, marked by an escalation of both extreme rainfall events and prolonged dry spells as the climate warms.
Trees as living climate archives
Each year, trees add a new growth ring, forming a natural archive of environmental conditions. In wet years, trees typically produce wider rings as water is readily available for growth, while dry years leave behind narrower rings as growth slows.
By measuring these rings and comparing patterns across many trees, scientists can piece together past climate conditions long before weather instruments existed, a practice known as dendroclimatology.
For this study, researchers focused on pine trees from high-elevation sites in eastern Spain, where growth is especially sensitive to changes in rainfall. Some of the sampled trees are several centuries old, allowing the team to build a continuous record stretching back to 1503.
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