Glossary

An extreme weather event is one that rarely occurs at a given place and in a given season. Although definitions of “rarely” vary, an extreme weather event would normally be as rare or rarer than the 10^th or 90^th percentile of the observed probability distribution. By definition, the characteristics of extreme weather can vary from place to place. Individual extreme events cannot simply and directly be attributed to anthropogenic climate change, as there is always a limited chance that the event in question could have occurred naturally. When a pattern of extreme weather continues over a certain timeframe, e.g. a season, it can be classified as an “extreme climate event”, especially when it is characterised by a mean value or sum that is itself extreme (e.g. a drought or heavy precipitation continuing for an entire season).