What is the primary effect of El Niño?

The primary effect of El Niño is the alteration of weather patterns globally. El Niño refers to the periodic warming of ocean surface temperatures in the central and eastern tropical Pacific, which significantly impacts atmospheric circulation patterns. This phenomenon can lead to a variety of weather changes across different regions, including increased rainfall in some areas and drought in others.

El Niño's influence on weather includes a shift in the jet streams, which affects storm tracks and precipitation. For example, areas like the western coast of South America often experience heavy rainfall and flooding, while regions such as Southeast Asia may see drier conditions. These widespread changes help explain why El Niño is recognized for its profound and varied impacts on global weather systems and climate.

This understanding clarifies why the other options do not accurately represent the primary effect of El Niño. Decreased ocean temperatures would actually describe La Niña, which is a counterpart to El Niño and has opposite effects. Consistent weather patterns do not characterize El Niño, as the phenomena are known for inducing variability. Lastly, increased pressure systems is misleading; El Niño alters pressure patterns, but it does not uniformly increase them, as these systems can change dynamically.