The influence of decision-making in tree ring-based climate reconstructions.

Area of Science:

• Paleoclimatology
• Climate Reconstruction
• Dendrochronology

Background:

• Tree-ring chronologies are essential for annually-resolved climate reconstructions of the Common Era.
• Existing reconstructions utilize diverse datasets and methodologies, with limited exploration of their comparative impacts.
• This study addresses the variability and subjectivity inherent in different tree-ring reconstruction techniques.

Purpose of the Study:

• To assess the influence of methodological choices on past climate reconstructions.
• To generate an ensemble of Northern Hemisphere summer temperature reconstructions using a common tree-ring dataset.
• To evaluate the robustness and agreement among multiple independent reconstructions.

Main Methods:

• A double-blind experiment was conducted using a shared network of regional tree-ring width data.
• Fifteen distinct summer temperature reconstructions for the Northern Hemisphere were produced.
• Statistical analysis was performed on the ensemble mean and individual reconstructions.

Main Results:

• The ensemble mean reconstruction strongly correlates with instrumental temperatures (0.79, p < 0.001) from 1794-2016 CE.
• The reconstructions capture known climate events, including cooling after major volcanic eruptions and significant warming since the 1980s.
• Individual reconstructions exhibited notable differences in mean, variance, amplitude, sensitivity, and persistence, indicating methodological influence.

Conclusions:

• Subjectivity in the reconstruction process significantly impacts climate reconstructions.
• Ensemble reconstruction approaches are recommended for a more consensual and reliable understanding of past climate variability.
• Standardizing or acknowledging methodological variations is crucial for improving paleoclimate reconstructions.