El Niño
El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO), a periodic climate pattern involving anomalously warm sea surface temperatures in the central and eastern tropical Pacific Ocean that typically occurs every 2 to 7 years and lasts 9 to 12 months. This ocean–atmosphere interaction disrupts normal trade wind patterns, suppresses the cold upwelling of the Peruvian coast, and triggers widespread alterations in global precipitation and temperature distributions. El Niño events are associated with droughts in Australia and South Asia, flooding in South America and East Africa, and unusually warm global mean temperatures.
Comparison of El Niño, La Niña, and Neutral ENSO Conditions
| Condition | Pacific SST | Trade Winds | Global Impact |
|---|---|---|---|
| El Niño (warm phase) | Above normal (east Pacific) | Weakened or reversed | Droughts in Australia/India, flooding in Americas |
| La Niña (cool phase) | Below normal (east Pacific) | Stronger than normal | Enhanced monsoons in Australia/India |
| Neutral | Near-average | Normal | Typical seasonal patterns |
| Strong El Niño (1997–98) | +2.5°C anomaly | Near-absent | Hottest year on record at that time |
| Strong La Niña (2010–11) | −1.5°C anomaly | Strengthened | Severe Australian flooding, Pakistan floods |
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Related Terms
Monsoon
A monsoon is a seasonal reversal of wind direction driven by differential heating between large landmasses and adjacent oceans, bringing a distinct wet season characterised by heavy, sustained rainfall. During summer, the land heats faster than the ocean, creating low pressure over the continent that draws in moist oceanic air; in winter, the land cools faster, reversing the flow and bringing dry continental air. The South Asian (Indian) Monsoon is the most significant, delivering approximately 80% of India's annual rainfall between June and September and sustaining over a billion people's agriculture and water supply.
Climate Change
Climate change refers to long-term shifts in global and regional climate patterns, including changes in temperature, precipitation, wind patterns, and the frequency of extreme weather events, driven largely by human activities since the mid-20th century. While Earth's climate has always varied naturally due to orbital cycles, volcanic eruptions, and solar variability, the current rate and magnitude of change are unprecedented in the geological record of the past 800,000 years. The primary driver is the increased atmospheric concentration of greenhouse gases from burning fossil fuels, deforestation, and agricultural practices.
Global Warming
Global warming refers to the long-term increase in Earth's average surface temperature, primarily caused by the enhanced greenhouse effect resulting from human-induced emissions of greenhouse gases such as carbon dioxide, methane, and nitrous oxide. Since the pre-industrial era (before 1850), global average temperatures have risen by approximately 1.2°C, with the rate of warming accelerating significantly since the mid-20th century. This warming drives profound changes in climate patterns, sea levels, ice cover, and biodiversity worldwide.
The name "El Niño" (Spanish: The Little Boy, or Christ Child) was given by Peruvian fishermen in the 19th century because the warm current typically arrived near Christmas. The full scientific term El Niño–Southern Oscillation (ENSO) was developed by Gilbert Walker and later Jacob Bjerknes in the 20th century, linking the oceanic and atmospheric components of the phenomenon.