Tuesday, January 1, 2013

New paper finds climate in Tibet was more stable in the 20th century than prior

A new paper published in Climate of the Past reconstructs the climate of southeast Tibet over 224 years from 1781-2005 and finds, "The climate appears drier and more stable in the 20th century than previously." The paper contradicts claims of climate alarmists that global warming causes an increase of extreme weather or extreme precipitation. In addition, the paper finds cloud cover decreased during the 20th century in comparison to the 19th century, which could amplify solar effects on temperature. According to the authors, "The occurrence of years of extreme low or high cloud index appears to have strongly decreased since the 1920s, suggesting a relatively stable summer moisture condition in southeast Tibet in spite of the increasing [alleged] impact of human activities on climate."

The paper adds to many other peer-reviewed papers demonstrating that a warmer climate is a more benign and stable climate, with less extremes of precipitation, floods, droughts, and weather.
Top graph shows dO18, a proxy for precipitation and temperature. Precipitation was more variable and extreme during the 19th century than the 20th. Bottom graph shows reconstructed cloud cover, with decreased cloud cover in the 20th century compared to the 19th. 
Clim. Past, 8, 205-213, 2012

Reconstruction of southeast Tibetan Plateau summer climate using tree ring δ18O: moisture variability over the past two centuries

C. Shi1,2,6, V. Daux2, Q.-B. Zhang1, C. Risi3, S.-G. Hou4, M. Stievenard2, M. Pierre2, Z. Li5, and V. Masson-Delmotte2

1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
2Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, IPSL/CEA/CNRS/UVSQ Bat 701, L'Orme des Merisiers, CEA Saclay, 91 191 Gif sur Yvette Cedex, France
3CIRES, University of Colorado, 80309 Boulder CO, USA
4Key Laboratory for Coast and Island Development, Ministry of Education, School of Geographic and Oceanographic Sciences, Nanjing University, 22 Hankou Road, Nanjing 210093, China
5Research center For Eco-Environment Change, Chinese Academy of Sciences, Beijing 100085, China
6Graduate School of Chinese Academy of Sciences, Beijing 100049, China

Abstract. A tree-ring δ18O chronology of Linzhi spruce, spanning from AD 1781 to 2005, was developed in Bomi, Southeast Tibetan Plateau (TP). During the period with instrumental data (AD 1961–2005), this record is strongly correlated with regional CRU (Climate Research Unit) summer cloud data, which is supported by a precipitation δ18O simulation conducted with the isotope-enabled atmospheric general circulation model LMDZiso. A reconstruction of a regional summer cloud index, based upon the empirical relationship between cloud and diurnal temperature range, was therefore achieved. This index reflects regional moisture variability in the past 225 yr. The climate appears drier and more stable in the 20th century than previously. The drying trend in late 19th century of our reconstruction is consistent with a decrease in the TP glacier accumulation recorded in ice cores. An exceptional dry decade is documented in the 1810s, possibly related to the impact of repeated volcanic eruptions on monsoon flow.

Final Revised Paper (PDF, 1927 KB)   Supplement (177 KB)   Discussion Paper (CPD)   

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