Archives par mot-clé : LIA

Solar forcing and climate variability during the past millennium as recorded in a high altitude lake: Lake Salda (SW Anatolia)

by I.B. Bauhi & S. Akçer-Ön, August 30, 2018 in QuaternaryInternational


Abstract

Climate variability is a well-known phenomenon and has been frequently, though complex, linked to solar forcing on different time scales. The importance of solar forcing related climate variability is crucial in our understanding of paleoclimate and future climate changes, as well as building climate models. Here in, we present the late Holocene (last ca 1400) climate records from Lake Salda in SW Anatolia using high-resolution micro X-ray Fluorescence (μ-XRF), magnetic susceptibility (MS), stable isotopes13C and δ18O) and TOC-TIC measurements. The age model is constructed by using radionuclide (210Pb, 137Cs and 14C) dating methods. The lake’s high-resolution multiproxy results revealed lake water level fluctuations associated with humid and dry spells during the last 1400 years. Periods of higher lake levels are consistent with solar maxima in total solar irradiance and vice versa. Moreover, the Lake Salda records clearly show dry Dark Ages Cold Period (DACP), humid Medieval Climatic Anomaly (MCA), dry Little Ice Age (LIA), and humid Modern Warm Period (MoWP). These records suggest that the solar forcing, through its influence on the atmospheric circulation, is the main mechanism of climate change during the DACP, MCA, LIA and MoWP in this region.

End of the Little Ice Age in the Alps forced by industrial black carbon

by Thomas H. Painter et al., September 17, 2018 in PNAS


The end of the Little Ice Age in the European Alps has long been a paradox to glaciology and climatology. Glaciers in the Alps began to retreat abruptly in the mid-19th century, but reconstructions of temperature and precipitation indicate that glaciers should have instead advanced into the 20th century. We observe that industrial black carbon in snow began to increase markedly in the mid-19th century and show with simulations that the associated increases in absorbed sunlight by black carbon in snow and snowmelt were of sufficient magnitude to cause this scale of glacier retreat. This hypothesis offers a physically based explanation for the glacier retreat that maintains consistency with the temperature and precipitation reconstructions.

How the Little Ice Age affected South American climate

by Fundação de Amparo à Pesquisa do Estado de São Paulo, July 24, 2018 in ScienceDaily


A new study published in Geophysical Research Journal shows that the so-called Little Ice Age — a period stretching from 1500 to 1850 in which mean temperatures in the northern hemisphere were considerably lower than at present — exerted effects on the climate of South America.

Based on an analysis of speleothems (cave formations) in the Brazilian states of Mato Grosso do Sul and Goiás, the study revealed that in the seventeenth and eighteenth centuries, the climate of southwestern Brazil was wetter than it is now, for example, while that of the country’s Northeast region was drier.

The same Brazilian cave records showed that the climate was drier in Brazil between 900 and 1100, during a period known as the Medieval Climate Anomaly (MCA), when the northern hemisphere’s climate was warmer than it is now.

 

Le climat et son histoire

by Emmanuel Le Roy Ladurie, 2012 in CairnInfo


Beaucoup de gens, à juste titre, sont impressionnés par les prédictions pessimistes du GIEC  relativement à la fin du xxie siècle, et il est fort possible que ces prédictions soient justifiées. La tâche de l’historien, c’est plutôt de resituer l’histoire du climat dans des périodes récentes ou moins récentes et de réfléchir, ensuite, en toute indépendance, en toute objectivité, sur ce qui nous attend, tant en fonction de ce qui s’est passé déjà, qu’en fonction des résultats impressionnants que nous proposent, avec raison sans doute, les sciences exactes.