Climate is the measure of weather patterns over a long period of time, and inherent to climate are changes, both long-term and short-term. Short-term climate changes represent periodic or intermittent changes that occur, and this is termed "climate variability." These short-term changes might include floods, drought, temperature changes or oscillating weather patterns such as the effects of El Niño or La Niña. In the most general sense, climate variability is thought of as the deviations in climate statistics over a long period of time. Accurately identifying and understanding climate variations is important to recognizing and understanding their effect on humans.
The term "climate" is a term that is used to describe the average mix of meteorological conditions in a geographical location over the long term. Scientists determine the climate of a geographic location by compiling statistics over an extended time period, usually several decades or longer. Such statistics include the value, variance and probabilities associated with meteorological conditions such as temperature, humidity, precipitation and wind.
When scientists study climate over the long term, they often find inconsistencies in weather when compared to the average. For example, climates that normally are wet might experience dry spells or even droughts because of a change in weather patterns. Although these short-term changes are inherent, they don’t mean that the climate has changed. Instead, they simply are a deviation from the region's accustomed climate. Scientists assign the term "climate variability" to identify such anomalies, which usually last for less than a decade.
There are many reasons why climates deviate from the norm. One of the most distinguishable natural variations in climate occurs with the El Niño-southern oscillation (ENSO) circumstance. ENSO explains the interaction of the Pacific Ocean with the atmosphere, creating global climate deviations. Every few years, there are changes in the ocean surface temperature and other meteorological elements around the Pacific equator. Colder temperatures characterize La Niña, and warmer temperatures are the signature of the El Niño cycle. The different temperatures produce variations in tropical rainfall, agitating climates all over the world.
The study of climate variations is important to scientists because of its effect on people. If scientists can identify patterns or discern the effect on weather attributed to climate variability, people usually can acclimate. To illustrate, scientist have placed an observation system in the tropical Pacific that allows forecasting of the El Niño affects several years before they manifest in the global climate. This information can help calculate resulting conditions such as intensified storms or drought conditions ahead of time.
By contrast, when scientists fail to understand climate variability, people usually suffer. For example, the Dustbowl of the 1930s is believed to have been caused by climate variability associated with warmer ocean temperatures over the Atlantic Ocean and La Niña effects in the Pacific Ocean. If these effects had been known ahead of time, rather than decades later, scientists could have warned about the resulting consequences.