Abstract
AbstractSystematic comparisons of proxy-based reconstructions and climate model simulations of past millennium temperature variability offer insights into climate sensitivity and feedback mechanisms, besides allowing model evaluation independently from the period covered by instrumental data. Such simulation–reconstruction comparisons can help to distinguish more skillful models from less skillful ones, which may subsequently help to develop more reliable future projections. This study evaluates the low-frequency simulation–reconstruction agreement within the past millennium through assessing the amplitude of temperature change between the Medieval Climate Anomaly (here, 950–1250 CE) and the Little Ice Age (here, 1450–1850 CE) in PMIP3 model simulations compared to proxy-based local and continental-scale reconstructions. The simulations consistently show a smaller temperature change than the reconstructions for most regions in the Northern Hemisphere, but not in the Southern Hemisphere, as well as a partly different spatial pattern. A cost function analysis assesses how well the various simulations agree with reconstructions. Disregarding spatial correlation, significant differences are seen in the agreement with the local temperature reconstructions between groups of models, but insignificant differences are noted when compared to continental-scale reconstructions. This result points toward a limited possibility to “rank” models by means of their low-frequency temperature variability alone. The systematically lower amplitude of simulated versus reconstructed temperature change indicates either too-small simulated internal variability or that the analyzed models lack some critical forcing or have missing or too-weak feedback mechanisms. We hypothesize that too-cold initial ocean conditions in the models—in combination with too-weak internal variability and slow feedbacks over longer time scales—could account for much of the simulation–reconstruction disagreement.
Highlights
Understanding the variability of temperature at local to global scales, over the past one to two millennia, offers insight into natural decadal to centennial-scale change that cannot be discerned from instrumental data
After comparing the MCA–LIA temperature difference in the PMIP3 simulations with local and continentalscale temperature reconstructions, we conclude the following: 1) Both local and the continental-scale reconstructions on average show a larger amplitude of temperature change than the simulations in the Northern Hemisphere (NH), in the high latitudes
4) It is difficult to evaluate the degree of agreement between reconstructed and simulated Arctic/polar amplification as only some models show a significant amplification while others do not
Summary
Downloaded from http://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-18-0525.1 by guest on 05 October 2020 FREDRIK CHARPENTIER LJUNGQVIST,a,b,c QIONG ZHANG,d,b GUDRUN BRATTSTRÖM,e,b PAUL J. KRUSIC,c,d ANDREA SEIM,f QIANG LI,d,b QIANG ZHANG,d,b AND ANDERS MOBERGd,b a Department of History, Stockholm University, Stockholm, Sweden b Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden c Department of Geography, University of Cambridge, Cambridge, United Kingdom d Department of Physical Geography, Stockholm University, Stockholm, Sweden e Department of Mathematics, Stockholm University, Stockholm, Sweden f Chair of Forest Growth and Dendroecology, Institute of Forest Sciences, University of Freiburg, Freiburg, Germany (Manuscript received 14 August 2018, in final form 3 February 2019)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
