What phenomenon typically signals the start of El Niño events?

• A. Cool water temperatures
• B. Higher atmospheric pressure
• C. Warm water temperatures
• D. Seasonal monsoons

Answer: (C)

The correct answer is warm water temperatures, as this is a key indicator of El Niño events. During an El Niño, the usual trade winds weaken significantly, which allows warmer waters from the western Pacific to shift eastward toward the coasts of South America. This increase in sea surface temperatures in the central and eastern Pacific is crucial because it disrupts normal weather patterns, leading to a range of climatic effects globally, including altered precipitation and temperature patterns.

In contrast, cool water temperatures would indicate a La Niña event rather than an El Niño, and higher atmospheric pressure is generally associated with La Niña conditions as well. Seasonal monsoons occur in certain regions regardless of El Niño's presence and are not specific indicators of the phenomenon. Understanding the role of warm water temperatures in initiating El Niño helps to contextualize its broader impacts on climate and weather patterns worldwide.