June 28, 2023

El Niño: how the weather event is affecting global heating in 2023

El Niño can cause an increase in global temperatures. The ocean plays a big role in absorbing heat from greenhouse gases that come from burning fossil fuels and other human activities. Normally, during a La Niña event, the ocean does a good job of absorbing this heat, especially in the East Pacific where temperatures are very cold.

Easterly winds usually push warm surface waters in the equatorial Pacific towards Australia and Indonesia and away from South America. This causes warm water to accumulate in the west Pacific and draws up cool water from deeper parts of the east Pacific. This is called the neutral state. However, during El Niño, the easterly winds weaken and warm water spreads across the entire Pacific. This can cause global surface temperatures to go up by as much as 0.2°C each year.

The areas closest to the Pacific Ocean are the most strongly affected by El Niño. In Peru and Ecuador, El Niño brings heavy rainfall and flooding. The event is called El Niño de Navidad, or the Christ Child, because it mainly occurs during Christmas time in that region.

In the Amazon, El Niño causes the weather to become hotter and drier. This leads to less vegetation growth and a higher risk of forest fires, which is already a concern. El Niño also brings increased heat and drought to Colombia and Central America.

Australia can suffer from severe impacts due to the hotter temperatures brought by El Niño on the other side of the Pacific. This raises the likelihood of heatwaves, drought, and bushfires in the eastern part of the country. Additionally, it increases the chances of extensive coral bleaching in the Great Barrier Reef. The "black summer" of 2019-20 occurred during a minor El Niño event. Indonesia also faces an increased risk of drought, and during the last major El Niño from 2014-2016, it experienced massive forest fires that produced a smoke plume that traveled halfway across the globe.

Even countries farther from the equator experience significant effects from El Niño, as it alters the position of the strong winds in the high-altitude jet stream. Consequently, the southern United States receives more rainfall, leading to an increased risk of floods. Conversely, the northern United States and Canada experience warmer and drier conditions. The situation is similar in China, with the southern region becoming wetter and the northern region becoming hotter and drier.

El Niño impacts places far from the Pacific, affecting the global climate system. One major impact is reduced rainfall in the Indian monsoon, which provides 70% of the country's water and is crucial for growing food in the world's most populous nation. However, El Niño could bring more rain to the drought-stricken Horn of Africa, where dry conditions worsened by consecutiveLa Niña have caused a long-term drought in parts of Ethiopia, Kenya, andSomalia.

El Niño also influences the risk of hurricanes and typhoons. It usually weakens the ones that affect the Caribbean, the United States, India, Bangladesh,Japan, and Korea. However, these storms rely on warm ocean temperatures, and the record-high sea temperatures in the Atlantic in 2023 have led the UK MetOffice to predict an above-average number of tropical storms in the NorthAtlantic.

Europe is less affected, but during winter, El Niño can shift the jet stream, resulting in more rain in the south and drier, colder conditions in the north.

El Niño's impact on rainfall, temperature, and plant growth has cascading effects. It can increase the risk of infectious diseases like dengue fever inSoutheast Asia and Brazil. Some studies have even linked lower food production during El Niño years to civil conflicts.

Currently, weak El Niño conditions began in May and are expected to strengthen in the upcoming months. There is an 84% chance of a moderate event reaching its peak from November to January.

Global average temperatures in early June were almost 1 degree Celsius higher than previously recorded levels for the same month. This resulted in unprecedented heatwaves in various regions, including Puerto Rico, Siberia, andChina. Some scientists predict that 2023 could be the hottest year on record due to this warming. However, the majority of the heat from El Niño is expected to occur in 2024.

The impact of human-caused climate change on El Niño and La Niña events is still uncertain. This is partly due to the limited number of recorded El Niño and La Niña occurrences, spanning approximately 150 years. Consequently, it is challenging to determine whether the observed trends, indicating a potential increase in La Niña events, are simply a result of chance. Climate models do not agree on this. They have a low resolution and struggle to accurately represent the ocean dynamics and cloud patterns in the tropical Pacific.

One thing is clear: as global temperatures rise, extreme weather events will become more severe, especially during El Niño years. This will continue until carbon emissions reach zero.