Old World megadroughts and pluvials during the Common Era

Area of Science:

• Paleoclimatology
• Climate Science
• Environmental History

Background:

• Climate models project significant hydroclimatic shifts in the Mediterranean and Fennoscandia due to greenhouse gas emissions.
• Understanding natural hydroclimatic variability is essential for contextualizing future climate change.
• Historical climate data often lacks the spatial completeness to assess past drought and wetness events comprehensively.

Purpose of the Study:

• To develop a comprehensive dataset of past hydroclimatic variability across the "Old World" (Europe and the Mediterranean Basin).
• To provide historical perspective on current and future climate projections by reconstructing natural climate variability.
• To investigate the causes of past drought and wetness events and attribute them to forced or internal climate variability.

Main Methods:

• Construction of the "Old World Drought Atlas" (OWDA) using tree-ring data.
• Year-to-year mapping of reconstructed summer wetness and dryness across Europe and the Mediterranean Basin.
• Integration of paleoclimate reconstructions with historical accounts of drought and wetness.

Main Results:

• The OWDA provides unprecedented spatial completeness for reconstructing past hydroclimatic conditions.
• Reconstructions reveal severe megadroughts in north-central Europe during the 11th and mid-15th centuries.
• Evidence suggests pre-20th century droughts in the Northern Hemisphere were more severe, extensive, and prolonged than previously understood.

Conclusions:

• The OWDA offers a valuable new resource for understanding the full spectrum of hydroclimatic variability in the Old World.
• The findings highlight the need for further research into the causes of past severe droughts.
• This atlas will aid in attributing past climate variability to natural or anthropogenic forcing.