Developing El Niño has potential to become strongest ever

The world is facing the prospect of an unprecedented El Niño event over the coming months, with the United Nations warning of widespread disruption to global weather patterns, increased drought and flooding, and potentially escalating humanitarian emergencies.

The World Meteorological Organization (WMO) says sea surface temperatures in a key monitoring region of the tropical Pacific could rise to an extraordinary 3.8°C above average during November, December and January.

The organisation's Secretary General Celeste Saulo described the developing event as potentially the strongest ever recorded.

"This is literally off the monitoring charts that we have used for the past four decades. El Niño will peak towards the end of 2026, but its impacts will be felt long after that," she said.

The forecast is particularly significant because the WMO's threshold for identifying El Niño conditions is a sea surface temperature anomaly of just 0.5°C in the tropical Pacific.

The projected 3.8°C anomaly refers specifically to ocean temperatures in the El Niño monitoring region, rather than an increase in average global sea temperatures.

El Niño is a naturally occurring climate phenomenon involving unusually warm ocean waters in the central and eastern tropical Pacific.

It can disrupt atmospheric circulation and rainfall patterns across large parts of the world, bringing severe drought to some regions and unusually heavy rainfall and flooding to others.

It can also contribute to higher global temperatures, temporarily amplifying the underlying warming of the planet caused by greenhouse gas emissions.

The latest forecast therefore raises concerns about the potential for exceptionally high global temperatures during 2027, as the influence of a powerful El Niño can continue for months after the event itself reaches its peak.

While El Niño can have profound consequences for weather patterns internationally, its direct influence on Ireland is considerably less predictable.

Irish winter weather is influenced primarily by atmospheric circulation over the North Atlantic, including the position of the jet stream and the North Atlantic Oscillation.

Consequently, even an exceptionally powerful El Niño does not necessarily mean Ireland will experience an unusually mild, wet or stormy winter.

However, a separate seasonal outlook issued by Met Éireann yesterday points towards a relatively mild and wetter-than-average start to winter.

Its forecast for November through January indicates that average temperatures across Ireland could be between 0.5°C and 1°C above normal.

Rainfall is also expected to be above average overall, with the strongest signal for wetter conditions during November and December, particularly in southern parts of the country.

Sea temperatures around Ireland are also forecast to remain between 0.2°C and 1°C above normal.

Read more: El Niño to intensify before December peak - UN's World Meteorological Organization

This suggests the prospect of a relatively mild but unsettled beginning to winter, although Met Éireann cautions that colder-than-average spells remain possible, particularly towards the latter part of the forecast period.

Seasonal forecasts describe the likelihood of broad weather patterns over several months. They cannot reliably predict individual storms, flooding episodes, snowfalls or prolonged cold spells this far in advance.

Those displaced or living in conflict zones 'vulnerable'

Speaking at a press conference the WMO Secretary-General Celeste Saulo, warned that the consequences of the developing El Niño could be particularly severe for populations already struggling with conflict, displacement and humanitarian crises.

"A very strong El Niño disrupts normal temperature and rainfall patterns across many regions," she said.

"We are already witnessing extreme weather events and expect these to multiply – and cascade – as El Niño intensifies."

She warned that refugees, displaced populations and communities living in conflict zones were especially vulnerable because housing, water, sanitation and healthcare services were already under considerable pressure.

However, she emphasised that the availability of increasingly sophisticated climate forecasts and early-warning systems provided an opportunity to reduce the human consequences of the developing event.

Nevertheless, she warned that the opportunity to prepare was limited as time is running out.