The most severe droughts in the ancient Eastern Mediterranean arose when multiple natural climate cycles coincided, according to a new study from Stockholm University published in Science Advances. The findings shed new light on the climate conditions surrounding the Late Bronze Age collapse and may help improve understanding of future drought risks in a warming world.

“Rather than being caused by a single climatic event, we found that the most extreme droughts emerged when natural climate cycles operating over different timescales coincided. This helps explain why the drought associated with the Late Bronze Age collapse were so severe”, says Katherine Power, PhD student, Department of Physical Geography, Stockholm University, and first author of the study.

Around 3,200 years ago, many of the great civilizations of the Eastern Mediterranean, including the Mycenaeans, Minoans and Hittite Empire, experienced widespread societal collapse. Although severe droughts have long been linked to this period, the climatic processes behind these events remain uncertain. To investigate this, Katherine Power and Qiong Zhang, professor in paleoclimate modelling, Department of Physical Geography, Stockholm University and co-author of the study, used a state-of-the-art climate model to reconstruct the evolution of the Mediterranean climate over the past 8,000 years.

“Our results show that the region underwent a gradual drying trend over thousands of years, driven by slow changes in Earth’s orbit. Superimposed on this long-term trend we also found shorter-term fluctuations in the Atlantic Ocean and atmosphere”, says Katherine Power.

The researchers found that most severe droughts occurred when several natural climate cycles aligned, temporarily reinforcing one another and producing droughts far more intense than the long-term drying trend alone.

“The convergence of these processes pushed the Eastern Mediterranean beyond a critical hydroclimatic threshold, reducing water availability and increasing pressure on agriculture and food security within already vulnerable societies”, Katherine Power says.

These findings change how we think about past droughts, the researcher say, and understanding these processes is highly relevant today:

“The Mediterranean is one of the world’s climate change hotspots and the area is projected to become warmer and drier during the coming century. Our findings suggest that future drought risk may depend not only on long-term human-driven warming, but also on how natural variability in the Atlantic Ocean interacts with that background trend”, Katherine Power explains.

By revealing how different climate processes combine to amplify drought, this research can provide new insights into the risks of future hydroclimatic extremes in a warming world, the researchers say.

The study “Holocene ocean-atmosphere coupling and Mediterranean sensitivity to Atlantic circulation: Lessons from the Late Bronze Age collapse” was published in Science Advances. DOI: 10.1126/sciadv.aed5439.
For this research the model EC-Earth was used.