El Nino impacts the planet in two related ways. The first has to do with the way it influences weather patterns by altering the oceans and atmosphere, while the second relates to how those changes affect our property, food, water and health.
A strong El Nino can have a big impact on global weather patterns because it changes the way air circulates in the atmosphere. These circulations are determined by Earth's rotation, the angle of its axis relative to the sun, and the position of its landmasses and oceans. Significantly for El Nino, such air movements can also be influenced by dense tropical rainclouds that form over warm parts of the ocean [source: National Weather Service].
One circulation feature that you may have heard of is the jet stream — a narrow river of strong wind that circles the globe from west to east in our upper atmosphere. When El Nino shifts warm water to the eastern Pacific, the dense tropical rainclouds in the atmosphere above shift the jet stream as well, influencing weather hundreds or even thousands of miles down the line. These changes in atmospheric circulation and the altered weather patterns that result are just one example of what are called El Nino teleconnections [source: Barnston].
So how does all this wacky weather affect people's daily lives? Well, with all the fires, floods, storms and mudslides, property is certainly at risk. Take the 1997-1998 El Nino we mentioned earlier. By the time the warm waters retreated from the eastern Pacific in May 1998 it had caused some $33 billion in damage — a half billion in California alone [sources: Suplee, Linn and Mai-Duc].
Just as significant is the way El Nino interrupts the world's water supply, food production and human health. Many small Pacific Islands, for example, rely on rainfall and groundwater for their freshwater, so drought puts them at increased risk of coming up short [source: PacOOS]. Food crops also suffer from periods of drought, and unusually warm ocean water can disrupt fisheries. Anchovies, which are usually prolific in the cold waters off the coast of Peru, flee for colder waters to the south when things start to heat up [source: Suplee]. And if threatening our food and water isn't bad enough, El Nino can also be bad for your health: Warm, wet conditions are ideal for disease-carrying rodents and insects [source: WHO].