El Niño and La Niña
We conclude this study session by mentioning two natural climate cycles that can affect the location and frequency of extreme weather events around the world. The rise in sea temperature that we described in Study Session 9 has widespread effects on ocean currents, particularly in the Pacific Ocean (National Weather Service, 2006). When the Pacific Ocean is unusually warm, it generates a climate cycle known as El Niño (‘little boy’ in Spanish); when the ocean temperature is unusually cool, the climate cycle is called La Niña (‘little girl’). El Niño and La Niña have opposite effects on the climate. These ocean currents influence the route and speed of major airstreams and alter the pattern of rainfall around the world, so that some regions are wetter than average, and others are drier (Waskom et al., 2013).
In the next study session, you will look in more detail at the impacts of climate change and extreme weather events on health, environments, agriculture, water resources and the economy.