How El Niño and La Niña cause extreme weather

Summary

The video explains the El Niño Southern Oscillation (ENSO) and its two extreme phases, El Niño and La Niña, which drive extreme weather worldwide. It covers their history, mechanics, and global impacts, from droughts and floods to hurricanes and heatwaves. El Niño warms the Pacific, suppressing nutrient-rich upwelling and causing widespread droughts and storms, while La Niña cools the Pacific, boosting fisheries but also triggering floods and droughts in different regions. The film highlights the increasing intensity of ENSO events, their interplay with climate change, and the importance of preparedness, emphasizing that ENSO remains a major, somewhat predictable force shaping Earth's climate.

Takeaways

• 🌎 Extreme weather events worldwide, such as record snowfall, rainfall, and temperatures, are increasingly common and can devastate ecosystems, economies, and communities.
• 🌊 El Nino and La Nina are opposite phases of the El Nino Southern Oscillation (ENSO), a critical interaction between the Pacific Ocean and atmosphere affecting global climate.
• 🎣 El Nino, the warm phase, occurs when trade winds weaken, allowing warm water to remain in the central and eastern Pacific, reducing nutrient-rich upwelling and impacting fisheries.
• ☀️ El Nino brings far-reaching extreme weather, including droughts in northern US and Canada, wet conditions in Peru, and dry conditions in parts of Asia and Australia.
• 💰 The 1997–1998 El Nino caused catastrophic weather globally, resulting in 23,000 deaths and economic losses between $60–180 billion in today's money, while also contributing to record global temperatures.
• 🌬️ La Nina, the cool phase, strengthens trade winds, pushes warm water west, and increases upwelling, benefiting fisheries but also causing extreme weather such as hurricanes, floods, and droughts.
• 🌧️ Recent La Nina events led to severe flooding in Pakistan and droughts in East Africa, affecting tens of millions of people and causing billions in damages.
• 🔥 Climate change interacts with ENSO, amplifying extreme events, such as faster glacier melt contributing to floods, though the exact impact on ENSO patterns remains uncertain.
• 📈 Since 1950, ENSO events have been intensifying, causing greater sea surface temperature variations, but long-term historical patterns show ENSO naturally fluctuates over thousands of years.
• 📊 Climate models suggest ENSO will continue influencing rainfall variability, especially in the East Central tropical Pacific, highlighting the need for proactive resource allocation and preparedness.
• 🌀 ENSO is somewhat predictable, making early warnings and preparedness crucial to mitigate human, economic, and environmental impacts.

Q & A

What is the El Nino Southern Oscillation (ENSO)?

ENSO is a climate phenomenon that involves the interaction between the Pacific Ocean's sea surface temperatures and the atmosphere above it, measured through changes in water temperature and atmospheric pressure. It has three states: neutral, El Nino (warm phase), and La Nina (cool phase).

How did the term 'El Nino' originate?

Peruvian fishermen in the 17th century noticed periods of unusually warm Pacific waters around Christmas and called it 'El Nino,' meaning 'the boy' in Spanish, referencing the Christ child. The term was later linked to the Southern Oscillation and combined into ENSO.

What happens during the neutral phase of ENSO?

In the neutral phase, trade winds blow from east to west along the Equator, moving warm surface water toward Asia and Australia. This pushes the thermocline down in the west and up in the east, causing upwelling of cold, nutrient-rich water off the coast of South America, which supports rich fisheries.

How does El Nino affect global weather?

El Nino weakens trade winds, allowing warm water to remain in or move to the eastern Pacific. This disrupts upwelling, reduces fish populations, and causes extreme weather: drought in northern US and Canada, tropical storms on the west coast of the Americas, wet weather in Peru, dry conditions in Brazil and parts of Asia, and potential flooding in East Africa.

What are the economic and human impacts of El Nino?

The 1997 El Nino caused an estimated 23,000 deaths worldwide, with damage costs between 60 to 180 billion dollars in today's money. It also led to record global temperatures, disrupted fisheries, and severe droughts and floods across multiple continents.

How does La Nina differ from El Nino?

La Nina is the cool phase of ENSO, where stronger trade winds push more warm water west, making the thermocline shallower in the east and increasing upwelling off South America. This enhances fish populations but also leads to extreme weather, such as hurricanes in the Americas and flooding or drought in various regions.

What recent unusual pattern was observed with La Nina?

By early 2023, Earth experienced three consecutive Northern Hemisphere winters with La Nina, which is unusual since La Nina typically lasts 9–12 months. This contributed to heavy flooding, widespread drought, and severe impacts on food security and economies.

How does ENSO interact with climate change?

Climate change can amplify ENSO’s effects. For example, warming oceans store more heat, increasing the intensity of El Nino-related global temperature spikes. However, it's unclear how exactly climate change is altering ENSO patterns, as long-term natural variations complicate the analysis.

Why are ENSO events significant for tropical regions?

Over a third of the world’s population lives in the tropics, where ENSO causes pronounced year-to-year climate variability. Extreme rainfall or droughts during El Nino or La Nina events directly impact agriculture, water supply, and livelihoods in these regions.

What is the role of the thermocline in ENSO events?

The thermocline is the layer between warm surface water and cold deep water. During neutral ENSO, it rises in the east and sinks in the west, enabling upwelling. In El Nino, the thermocline flattens in the east, suppressing upwelling, while in La Nina it becomes shallower in the east, enhancing nutrient-rich upwelling.

What are some predictable patterns of ENSO that help in preparation?

ENSO is somewhat predictable because scientists can monitor sea surface temperatures in the Nino 3.4 region. Early forecasts allow governments and communities to allocate resources and prepare for expected droughts, floods, or storms.

How do extreme ENSO events affect global temperature trends?

El Nino releases stored ocean heat into the atmosphere, causing global temperature spikes, while La Nina tends to cool the world slightly. However, recent La Nina events still coincided with near-record global temperatures due to overall climate warming.