Analysis of SH Temperature Anomalies over the Last Millennium up to the Beginning of the Contemporary Age: A Comparison Between a Statistical Model and a Global Dynamic Model

MÜLLER GABRIELA V.; REPINALDO CINTIA R.; SHINDEL DREW; SCHMIDT GAVIN

Mendoza

Congreso; XI Congreso Argentino de Meteorología (CONGREMET XI); 2012

Centro Argentino de Meteorólogos

The purpose of the study is to analyze the consistency of the coupled atmosphere-ocean GISS-ER climate model in reproducing temperature anomalies during the last millennium, in South America. For that purpose, a comparison is performed between the model results and the temperature anomaly reconstruction provided by a statistical model that uses multiproxi data and climatological temperature anomalies (Neukom et al., Climate Dynamics, 2010). Considering the Neukom’s reconstruction, based on temperature anomalies from 1901-1995 for summer and winter, 6-member mean of the GISS-ER model with 1x and 2x solar forcing  are calculated for the period 1000-1899. Using the Neukom’s reconstructions, and the model’s outputs, are calculated the mean anomalies of the years between 1001 and 1700 (period that includes MCA and LIA) for the summer and 1706 and 1800 (period that includes the pre industrial period) for both summer and winter. These mean anomalies are subtracted from Neukom’s reconstructions defining the reconstructions wrt (with respect to) 1001-1700 (summer) and wrt 1706-1800 (summer and winter). Equally, with the model 6-member mean anomalies, defining the “Model 6-member mean wrt 1001-1700” for the summer (solar forcing 1x and 2x) and the “Model 6-member mean wrt 1706-1800 for both summer and winter (solar forcing 1x and 2x). In general, the model is not very consistent with the reconstructions, since it shows very small interannual variability in contrast to what the reconstructions exhibit, and often with opposite sign anomalies. In the 1001-1700 period the model presents, on average, negative temperature anomaly for the 1x and 2x forcing. In the 1706-1800 period, the model displays positive anomalies for summer and negative anomalies for winter for 1x and 2x forcing. The first period proved to be the most acceptable one, because it is longer, with more data, and provides more similar values to the reconstruction. In particular, the model 6-member mean that better reproduces the sign of the anomalies is wrt 1001-1700 with 1x forcing and for the summer season. The model presents an error of only 33% in reproducing the sign of the anomalies, in comparison to the Neukom’s reconstruction for the same reference period. The model 6-member mean wrt 1001-1700 with forcing 1x for summer also reproduces MCA and LIA’s sign. The MCA’s sign is reproduced in almost 75% of the comparisons, and the LIA’s sign in more than 73% of the comparisons, indicating that the model works better in the case of larger anomalies.