ESRL/PSD Seminar Series

Abstract

Climate models project a robust future drying of the climate in the Mediterranean Basin, related to the continued increase in greenhouse gas emissions. Observations show that most of the Basin exhibited a downward trend in winter precipitation in the second half of the 20th Century, so the question arises of whether this trend heralds the impact of anthropogenic climate change. We explore the cause of this long-term drying and show that most of it is related to the enigmatic upward trend in the strength of the North Atlantic Oscillation (NAO). There is however, an emergent, relatively smaller component of the recent drying that is of different origin. The latter is particularly strong in the Eastern Basin, over the Middle East and in the West, and over the Atlas Mountains of North Africa. We propose that this residual drying signal is an early expression of the anthropogenic forced climate change. We further show that this drying was implicated in the early 21st Century protracted drought in the Middle East, and did contribute, as many surmised, to the instability and eventual civil war in Syria.