Keeping a cool head at a time of global warming

30th March 2009

Giuseppe Orombelli

Professor of Physical Geography and Geomorphology at the University of Milano-Bicocca – member of Accademia Nazionale dei Lincei

Biography

Giuseppe Orombelli is Professor of Physical Geography at the University of Milano-Bicocca where he teaches classes on Geomorphology. His research activity deals with field geology, stratigraphy, geological mapping: Greece and Turkey (1960-1966). Alpine geomorphology: rock avalanches, catastrophic floods, Alps, Pakistan. Glacial and Quaternary geology: piedmont glacier morainic systems, Northern Italy; glacial and lacustrine sediments, Indus valley, Pakistan; Late Glacial to Holocene glacier fluctuations: Italian Alps, Mt. Etna. Late Cenozoic glaciations, Holocene glacier fluctuations, Holocene raised beaches (Victoria Land, Antarctica). Glaciology: ice cores (Greenland – GRIP Project, Antarctica – EPICA Project). Past president of the Italian Quaternary Association, and of the Italian Glaciological Committee; vice-chairman of the Italian Antarctic Scientific Commission. Author of more than 150 publications.

Abstract

The most detailed and reliable record of variations in the atmosphere and in the earth’s climate over the last 800 thousand years is provided by the ice cores extracted from the Antarctic and Greenland polar ice caps. Eight great glacial-interglacial climatic cycles have succeeded one another in this interval of time, triggered by astronomical causes and amplified by terrestrial causes (CO2, atmospheric dusts, extension of the ice, etc.). The cold glacial phases lasted much longer than the warm interglacials. Superimposed over these cycles are other climatic variations, almost as broad but shorter in duration (around a millennium), abruptly beginning and ending over the space of a few years or decades. The climate system is thus unstable and subject to sudden changes. The variations of a number of greenhouse gasses were measured in the ice cores: this showed that CO2 and methane concentrations over the last 800 thousand years were consistently lower than current concentrations and that their increase, from the industrial revolution onwards, has been in the order of 38% and 150% respectively.