What is El Niño and will it lead to another record-breaking summer?

The UK sweltered in record-breaking heat last summer. Credit: PA

There have been a number of reports in the press recently about a global weather event known as El Niño which could bring another record-breaking year and unprecedented heatwaves.

The El Niño Southern Oscillation (or ENSO) forms part of a complex relationship between the ocean and the atmosphere and it has the power to cause changes in global temperature and rainfall.

It is the world's biggest climate driver, takes place in the southern tropical Pacific Ocean, and occurs every two to seven years.

Currently the hottest year on record is 2016 and global temperatures were driven by El Niño.

In its simplest form, El Niño is the redistribution of heat into the central southern Pacific Ocean which in turn drives the weather patterns across the Pacific and around the globe.

El Niño is the name given to the warm phase of this natural cycle compared to its counterpart La Niña - the cool phase.

The oceans store vast amounts of heat and energy. During El Niño events, the ocean heat is released into the atmosphere and redistributed around the globe. It is no coincidence the hottest years on record occur during El Niño years.

Over the past three years, this natural event has been in the cooler phase - La Niña, helping to suppress global average temperatures. Despite this, these last years have been some of the hottest on record.

Last year, heatwaves scorched the UK with the highest temperature on record being recorded in Lincolnshire on 19th July where the mercury climbed to 40.3C.

Wildfires devastated homes and the countryside in the south east and a national emergency was declared for extreme heat.

In the latest research, scientists have found that a strong El Niño could be brewing which will lead to significant global impacts.

During March and April it was observed warmer than average sea surface temperatures have occurred in the equatorial Pacific Ocean, suggesting El Niño could develop by the summer of 2023.

Temperature anomalies during ENSO during the early Spring. Showing El Nino events coinciding with warmest years. Data: GISTEMP Anomalies Credit: realclimage.org

Global temperatures have been on the rise since the industrial revolution due to man-made greenhouse gases being released into the atmosphere.

This has caused the average global temperature up by around 1.2°C compared to pre-industrial levels.

It is expected that we will exceed the 1.5°C between 2032 and 2042 if we do not make drastic cuts to our global emissions. However, the first year to occur before this window will likely be associated with a big El Niño event.

It’s thought that if an El Niño event develops this year, it could increase global temperatures by 0.2 to 0.25°C.

As El Niño takes a while to get going, climate scientists are unsure how it will impact the global average temperature for 2023. The peak tends to occur during the northern hemisphere winter, hence 2024 is much more likely to set a new global temperature record.

Warmer oceans can destroy marine life, lead to more extreme weather events and cause sea levels to rise. Even more so, warmer oceans are less efficient at absorbing greenhouse gases contributing further to rising global temperatures.

When was the last El Niño?The last El Niño event occurred in 2018-2019, however this was weak. The one prior to that was 2016 which saw a strong event take place and coincided with the hottest year on record globally.

Will the UK see another record-breaking summer like 2022?It's not straightforward. As El Niño takes time to develop scientists believe that 2024 is more likely to be a record-breaking year globally for average temperatures.

However, 2023 is expected to be in the top four hottest years, according to the latest research from Carbon Brief.

It is important to note this is taking into account the temperature for the whole year and not just one season. Therefore we can not assume that further heatwaves like 2022 will once again occur across the UK.

Nonetheless, as the impacts of man-made climate change continue to be felt around the world, the extreme temperatures we saw in 2022 will occur every 15 years by 2100.

Climate Change and El Niño

Latest research from the World Meteorological Organisation and the Met Office has found that there is a 66% chance that annual global surface temperature will temporarily exceed 1.5°C above pre-industrial levels for at least one of next 5 years.

And a 98% likelihood that at least one of next five years will be warmest on record. El Niño is likely to contribute to this.

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