Comment on "Atlantic and Pacific multidecadal oscillations and Northern Hemisphere temperatures"

Area of Science:

• Climate science
• Climate modeling

Background:

• Multimodel ensemble means are used to estimate forced climate response.
• Previous work suggested rescaled ensemble means offer unbiased estimates.

Purpose of the Study:

• To critically evaluate the methodology used to demonstrate unbiased climate response estimation.
• To investigate the nature of residual variability in climate model simulations.

Main Methods:

• Analysis of rescaled multimodel ensemble-mean time series.
• Examination of residual intrinsic variability in individual model simulations.

Main Results:

• The procedure for demonstrating unbiased estimates is flawed.
• Residual variability is dominated by the model's actual forced response.
• Ensemble-mean time series may not accurately represent forced climate signals.

Conclusions:

• The assertion of unbiased climate response estimation via rescaled ensemble means is challenged.
• The interpretation of residual variability needs re-evaluation in climate model analysis.