XWX meaning in Academic & Science ?

Extreme weather or extreme climate events includes unexpected, unusual, severe, or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Often, extreme events are based on a location's recorded weather history and defined as lying in the most unusual ten percent.

There is evidence to suggest that climate change is increasing the periodicity and intensity of some extreme weather events. Confidence in the attribution of extreme weather and other events to anthropogenic climate change is highest in changes in frequency or magnitude of extreme heat and cold events with some confidence in increases in heavy precipitation and increases in the intensity of droughts.

Extreme weather has significant impacts on human society as well as natural ecosystems. For example, a global insurer Munich Re estimates that natural disasters cause more than $90 billion global direct losses in 2015.