El Niño and La Niña: The Pacific's Weather Controllers
Ever wondered why some years bring unexpected droughts whilst others flood normally dry regions? The answer lies in the El Niño Southern Oscillation - a massive flip in Pacific Ocean currents that happens every 3-7 years.
During El Niño, warm ocean water flows east towards South America instead of west. This completely reverses the normal Walker Circulation pattern. Scientists define it as five consecutive months when ocean temperatures sit 0.5°C above average. The impacts are enormous - Southern Asia's vital monsoons weaken, affecting one in four people who depend on these seasonal rains.
La Niña creates the opposite effect, with temperatures 0.5°C below average for at least five months. Strong trade winds push warm water west, creating very low pressure over Australia and high pressure over South America. This intensifies normal weather patterns rather than reversing them.
Key Fact: The 1997-1998 El Niño caused 200 deaths and £9 billion in economic damage, showing just how powerful these cycles can be.
