How Does El Niño Disrupt Global Weather Patterns?

TL;DR

El Niño begins when Pacific winds weaken or reverse, allowing unusually warm water to build near South America and release heat into the atmosphere. That added energy changes pressure, winds, storms, and moisture patterns worldwide, producing drought, crop failures, and other disruptions. The event described was already unusually strong in August and expected to keep growing until its November or December peak.

Transcript

From the New York Times, I'm Michael Bubaro. This is the daily. A powerful super El Nino event is right now brewing deep within the Pacific Ocean. is back. The Climate Prediction Center gives a 69% chance this year's El Nino may be the strongest since 1950. The heat released by the Pacific Ocean during that event could spike temperatures into unsee... Read More

Key Insights

• El Niño is a natural planetary phenomenon caused by changes in the tropical Pacific Ocean, but its effects extend worldwide because warming in that region reorganizes atmospheric pressure, winds, storms, and moisture patterns.
• An El Niño is identified when sea surface temperatures in the monitored equatorial Pacific region are 0.5 degrees Celsius above their usual level, while a 2-degree Celsius difference is classified as a super El Niño.
• Normal Pacific trade winds move warm surface water from South America toward Asia and allow cold water to rise near South America. El Niño develops when those winds slow or reverse, leaving warm water to accumulate in the eastern Pacific.
• Pacific heat affects global weather by rising into the atmosphere as a warm column reaching about 10 kilometers, or 6 miles, high. This added energy changes atmospheric pressure and winds, redirecting storms and determining where moisture travels.
• El Niño has been observed indirectly for centuries, beginning with Spanish colonists in Peru noticing tropical fish near their shores around December. The name came from El Niño Navidad, a reference to the Christ child.
• The 1877 El Niño coincided with drought and famine across multiple countries, including Ethiopia, China, Egypt, Morocco, Brazil, and India. The famine killed an estimated 50 million people, about 3 to 4 percent of the global population.
• The discussed El Niño was already exceptionally large in August, months before its typical November or December peak. Scientists expected it to continue growing and potentially become the largest event in an approximately 80-year instrumental record.
• Early impacts were already visible across several continents, including an extended lack of major storms in Panama, exceptionally dry conditions in Ethiopia's highlands, a poor maize harvest in Kenya, and India's fifth-driest June.

Questions & Answers

Q: What is El Niño and how is it identified?

El Niño is a natural planetary phenomenon involving unusual changes in the tropical Pacific Ocean. Scientists monitor an equatorial region extending from the coasts of Peru and Ecuador toward the international date line. When its sea surface temperature remains 0.5 degrees Celsius above the usual level, the conditions qualify as El Niño. A difference of 2 degrees Celsius is classified as a super El Niño.

Q: How does El Niño form in the Pacific Ocean?

El Niño forms when winds that normally push warm surface water from South America toward Asia weaken or reverse. Under ordinary conditions, colder water rises to replace the displaced surface water near South America. When that circulation changes, warm water is no longer carried away and can accumulate in the eastern Pacific, reinforcing a feedback loop between the ocean and atmosphere.

Q: How does El Niño change weather around the world?

El Niño changes global weather by releasing an unusually large amount of Pacific Ocean heat into the atmosphere. The warm air can rise about 10 kilometers, or 6 miles, producing changes in atmospheric pressure and winds. Those changes can redirect storms and alter where moisture travels, causing rain to fall in unexpected places while other regions become unusually dry.

Q: What is the difference between El Niño and a super El Niño?

The distinction is based on how far sea surface temperatures rise above their usual level in the monitored tropical Pacific region. A temperature difference of 0.5 degrees Celsius meets the threshold for El Niño. A difference of 2 degrees Celsius qualifies as a super El Niño. The event discussed could approach a 3-degree difference, beyond the terminology described in the transcript.

Q: When does El Niño usually reach its peak?

El Niño normally reaches its peak around November or December. The timing helps explain why people in Peru historically noticed tropical fish arriving near their shores around December. The event discussed was already so large in August that its size would have ranked among the biggest recorded events even if it had stopped growing before its usual late-year peak.

Q: What historical disasters have been associated with El Niño?

A major El Niño in 1877 coincided with severe drought and famine across several countries. Ethiopia, China, Egypt, Morocco, Brazil, and India all experienced drought, with India particularly hard hit. The famine killed an estimated 50 million people, equal to roughly 3 to 4 percent of the population, although some locations were already experiencing drought before El Niño intensified the conditions.

Q: What early effects of the current El Niño were already visible?

Early effects were appearing across at least three continents. Panama had not experienced a major storm since May, raising concern because the Panama Canal relies on a rain-fed lake for its locks. Ethiopia's highlands had an exceptionally dry June and July, Kenya experienced a poor maize harvest, and India recorded its fifth-driest June. Southeast Asia and Australia were also areas of concern.

Q: Why could drought threaten operations at the Panama Canal?

The Panama Canal depends on water from a rain-fed lake to operate its locks. Panama is normally among the wettest countries on Earth, but it had not experienced a major storm since May during the period discussed. Continued dryness could therefore reduce the water available for canal operations, creating concern about the canal's viability as El Niño's impacts develop.

Summary & Key Takeaways

• El Niño develops in an equatorial Pacific region stretching from Peru and Ecuador toward the international date line. When its sea surface temperature stays at least 0.5 degrees Celsius above normal, scientists classify the conditions as El Niño. A gap of 2 degrees Celsius marks a super El Niño.

• Normally, winds push warm surface water from South America toward Asia, while colder water rises to replace it. During El Niño, those winds weaken or reverse. Warm water then accumulates farther east, releases heat high into the atmosphere, and changes pressure, winds, storms, and the movement of moisture worldwide.

• The event discussed was already large in August, even though El Niño typically peaks around November or December. Early effects included dry conditions affecting the Panama Canal, Ethiopia's highlands, Kenya's maize harvest, and India's rainfall. Scientists expected further growth and potentially record-setting intensity before the event reached its peak.