Dear Dr. Sjolte,

Thank you for submitting your manuscript ““Solar and volcanic forcing of North Atlantic climate inferred from a process-based reconstruction” to Climate of the Past.

Your manuscript has now been seen by two reviewers. Both reviewers are overall positive about your work, recommending publication after some moderate corrections. I therefore invite you to resubmit your manuscript taking all comments by the reviewers into account. Please mark in the text, any changes that you make to the manuscript.

Kind regards,
Marit-Solveig Seidenkrantz, co-Editor in Chief

Dear Dr. Sjolte,

Thank you for resubmitting your revised manuscript, which I have read thoroughly. However, before deciding on its further destiny, I would ask you to make a few minor clarifications in the text:

In the abstract you write: “While our results show significant correlation between solar forcing and the secondary circulation pattern on decadal (r = 0.29, p <0.01) and centennial timescales (r= 0.6, p < 0.01), we find no consistent relationship between solar forcing and NAO.”
Your conclusion states: “Using this approach, tropical volcanic forcing accounts for about 10% of the decadal to multi-decadal variability of the reconstructed NAO, while solar forcing accounts for about 40% of the variability of PC2 of reconstructed SLP on centennial timescales.”

In the caption of revised figure 2 you write: “Ensemble mean reconstructed NAO (PC1 of reconstructed SLP (Hurrell et al., 2013))…”


In the first couple of reads it made me somewhat confused, as SLP is after all used an an index of NAO and it was only when I finally noticed the difference in PC number and your much clearer statement in the introduction that I understood the conclusions: “We find the average response to major tropical volcanic eruptions to be a positive NAO for the five consecutive winters after eruptions, which is more persistent 20 than previous studies have shown. However, we find no persistent relationship between solar forcing and the NAO. On the other hand, we find a strong impact of solar forcing on the secondary modes of circulation represented by the second principal component (PC2) of reconstructed sea level pressure (SLP).We achieve the strongest correspondence between the solar forcing and reconstructed PC2 of SLP with a time lag of 5 years, indicating that an atmosphere-ocean feedback is in play. Taking this time lag into account we find a consistent relationship between PC2 of 25 reconstructed SLP and solar forcing on decadal to centennial time scales”.

I would therefore ask you to make this also clearer in the conclusions and abstract. Also, at one point you mention that PC1 of SLP = NAO, while PC2 of SLP may correspond to the East Atlantic pattern. Could you expand on this, if possibly also refer to this in the conclusions?

Kind regards,

Marit-Solveig Seidenkrantz
Co-Editor in Chief, Climate of the Past