THE BLOG
10/13/2014 09:52 am ET Updated Dec 13, 2014

We Did Read Your Article

Co-authored with Alexander Stine and Peter Huybers

Michael, we did read your article (Mann et al., 12012). Your hypothesis of missing rings during the coldest years would lead to missing tree-ring density measurements as well, and would bias density toward not showing the coldest temperatures. If the width is missing, so is the density. In our article, we are careful to point out that "[t]he generally cold bias we identify does not necessarily contradict Mann et al. [2012], however, as the cooling bias may overwhelm the influence of any missing rings" (Tingley et al., 2014). Having only studied a limited spatial domain and eruptions for which adequate instrumental data and evidence are available, it could be that the effect you hypothesize is simply not present, or at least not identifiable, for these two recent eruptions. As you indicate, however, there are a number of other studies that do directly disagree with your hypothesis of missing rings (Anchukaitis et al., 2012; Esper et al 2013a,b).

The main point of our paper is that Arctic tree ring density appears sensitive to variations in light availability. This could have implications for both the interpretation of the temperature response to volcanic eruptions as well as longer term changes in light availability that may have occurred in the latter half of the twentieth century. The climatic response to short-lived volcanic eruptions may not be appropriate for inferring long-term climate sensitivity to CO2 forcing, and, furthermore, estimates of the forcing associated with pre-instrumental eruptions remain uncertain (Masson-Delmotte et al., 2013). Our paper makes no attempt to estimate climate sensitivity, and we do not interpret our results as indicating any need for revision to current estimates of climate sensitivity.

Martin Tingley is Assistant Professor in the Department of Meteorology and Department of Statistics, Pennsylvania State University. Alexander Stine is Assistant Professor, Department of Earth and Climate Sciences, San Francisco State University. Peter Huybers is Professor of Earth and Planetary Sciences and Environmental Science and Engineering, Harvard University

References:

- Anchukaitis, K. J., P. Breitenmoser, K. R. Bria, A. Buchwal, U. B untgen, E. R. Cook,

- R. D. D'Arrigo, J. Esper, M. N. Evans, D. Frank, et al. (2012), Tree rings and volcanic cooling, Nature Geoscience, 5 (12), 836-837. http://www.nature.com/ngeo/journal/v5/n12/full/ngeo1645.html

- Esper, J., U. B untgen, J. Luterbacher, and P. J. Krusic (2013a), Testing the hypothesis of post-volcanic missing rings in temperature sensitive dendrochronological data, Dendrochronologia, 31 (3), 216-222. URL: http://www.sciencedirect.com/science/article/pii/S1125786513000258

- Esper, J., L. Schneider, P. J. Krusic, J. Luterbacher, U. B untgen, M. Timonen, F. Sirocko, and E. Zorita (2013b), European summer temperature response to annually dated volcanic eruptions over the past nine centuries, Bulletin of volcanology, 75 (7), 1-14. URL: http://link.springer.com/article/10.1007%2Fs00445-013-0736-z

- Mann, M. E., J. D. Fuentes, and S. Rutherford (2012), Underestimation of volcanic cooling in tree-ring-based reconstructions of hemispheric temperatures, Nature Geoscience, 5 (3), 202-205. URL: http://www.nature.com/ngeo/journal/v5/n3/full/ngeo1394.html

- Masson-Delmotte, V., M. Schulz, A. Abe-Ouchi, J. Beer, A. Ganopolski, J.F. González Rouco, E. Jansen, K. Lambeck, J. Luterbacher, T. Naish, T. Osborn, B. Otto-Bliesner, T. Quinn, R. Ramesh, M. Rojas, X. Shao and A. Timmermann, 2013: Information from Paleoclimate Archives. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. URL: http://www.climatechange2013.org/images/report/WG1AR5_Chapter05_FINAL.pdf

- Tingley, M. P., A. R. Stine, and P. Huybers (2014). Temperature reconstructions from tree-ring densities overestimate volcanic cooling, Geophysical Research Letters, DOI: 10.1002/2014GL061268. URL: http://onlinelibrary.wiley.com/doi/10.1002/2014GL061268/abstract