Are extreme weather events becoming more common? How do extreme weather events impact society? These are critical questions that must be examined as we confront the possibility that the world will experience a change in climate over the next century. Much of the research in climatology over the past decade has focused on potential changes in long-term averages of temperature, precipitation and other factors. However, it is becoming increasingly clear that changes in average values will be accompanied by changes in extreme events. Furthermore, extreme weather events will impact society to a greater extent as people around the world continue to locate in more hazard-prone areas such as coastal zones. This work aims to develop a comprehensive set of information about changes in extreme events by providing a review of the problems in data availability, quality and analysis that make deriving a clear picture of world-wide changes in extreme events so difficult.