— Ch. 1 · Defining The Extremes —
Extreme weather.
~4 min read · Ch. 1 of 5
A weather event becomes extreme when it falls outside the historical distribution for a specific location. Scientists use thresholds to identify these moments, often selecting events that exceed a certain percentile of intensity or frequency. The Intergovernmental Panel on Climate Change defines an extreme weather event as one that is rare at a particular place and time of year. This rarity typically means the event occurs as rarely as the 10th or 90th percentile of a probability density function estimated from observations. In contrast, the World Meteorological Organization defines severe weather as any aspect posing risks to life, property, or requiring authority intervention. Severe weather represents a specific subset of all extreme weather events. One way to judge which events are extreme involves looking at accumulated cyclone energy charts or standard deviations above average temperatures.
Heat And Cold Waves
The European heat waves from summer 2003 caused an estimated 30,000 excess deaths due to heat stress and air pollution. During excessive heat, plants shut their leaf pores to conserve water, leaving more ozone in the air and leading to higher mortality rates. A hot summer in the UK during 2006 cost 460 lives through this mechanism alone. The worst heat wave in the United States occurred in 1936 and killed more than 5,000 people directly. Australia suffered its worst heat wave between 1938 and 1939, resulting in 438 fatalities. Power outages frequently occur within areas experiencing these heat waves due to increased electricity demand for air conditioning. Urban heat islands can increase temperatures, particularly overnight, trapping heat within city centers. Conversely, cold waves involve rapid falls in temperature within a 24-hour period requiring substantial protection for agriculture and commerce. Exposure to prolonged cold mandates greater caloric intake for humans and livestock alike. Poorly insulated water pipes often freeze during extreme winter cold, causing property damage when frozen water expands within them.