Progress in Physical Geography 31(1) (2007) pp. 77–87 © 2007 SAGE Publications DOI: 10.1177/0309133307073885 I Introduction – why are extremes important? Extreme weather and climate events can produce severe impacts on our society and environment. For instance, heat waves can be devastating for societies that are not used to coping with such extremes. More than 500 people died from heat-related illnesses in the 1995 Chicago heatwave (Karl and Knight, 1997). Over 30,000 deaths were attributable to the 2003 heatwave in Europe (about 15,000 deaths in France alone; IFRCRC, 2004; Poumadere et al., 2005) which also led to the destruction of large areas of forests by fire, and effects on water ecosystems and gla- ciers (Gruber et al., 2004; Koppe et al., 2004; Kovats et al., 2004; Schär and Jendritzky, 2004). European drought conditions during the summer of 2003 caused crop losses of around US$13 billion, while forest fires in Portugal were responsible for an additional US$1.6 billion in damage (Schär and Has the climate become more variable or extreme? Progress 1992–2006 Neville Nicholls* and Lisa Alexander School of Geography and Environmental Science, Building 11, Monash University, Victoria 3800, Australia Abstract: In 1990 and 1992 the Intergovernmental Panel on Climate Change (IPCC), in its first assessment of climate change and its supplement, did not consider whether extreme weather events had increased in frequency and/or intensity globally, because data were too sparse to make this a worthwhile exercise. In 1995 the IPCC, in its second assessment, did examine this question, but concluded that data and analyses of changes in extreme events were ‘not comprehensive’ and thus the question could not be answered with any confidence. Since then, concerted multinational efforts have been undertaken to collate, quality control, and analyse data on weather and climate extremes. A comprehensive examination of the question of whether extreme events have changed in frequency or intensity is now more feasible than it was 15 years ago. The processes that have led to this position are described, along with current understanding of possible changes in some extreme weather and climate events. Key words: climate change, frost, greenhouse effect, heat waves, weather extremes. *Author for correspondence. Email: neville.nicholls@arts.monash.edu.au  by guest on October 23, 2015 ppg.sagepub.com Downloaded from