El Niño and AMOC explained: How do they impact our weather in 2027?
Life-threatening cyclones, devastating forest fires, dramatic flash floods – we often view extreme weather events as something happening far away, something we only see on the news. Yet extreme weather events affect us all – even when they originate half a world away.
How do El Niño and AMOC affect the weather?
An El Niño event is currently developing in the Pacific and its effects will be visible in Europe, as well – models and forecasts can assess how. But El Niño is not the only mechanism through which the oceans influence our climate. Another 'climate engine' is the AMOC, the Atlantic Meridional Overturning Circulation, whose weakening or possible collapse would have serious consequences for the global ecosystem and climate. Susanna Winkelbauer and Michael Mayer from the Department of Meteorology and Geophysics at the University of Vienna explain how the oceans regulate the global climate, what role El Niño and the AMOC play in this, and what effects Europe and the world can expect.
A so-called 'El Niño' event is currently developing in the tropical Pacific. Forecast models agree that it is likely to be the strongest event since records began.Michael Mayer
What is 'El Niño'?
Michael Mayer: El Niño is one of the most far-reaching global climate phenomena. During this event, the entire tropical Pacific warms to unusually high temperatures and, as a result, vast amounts of energy are transferred from the ocean to the atmosphere, which in turn causes significant anomalies in atmospheric circulation and precipitation patterns.
Why is El Niño expected to be so strong in 2026?
Mayer: El Niño is a natural phenomenon that occurs every three to seven years. Its intensity varies from one event to the next. This year, we are forecasting a particularly strong El Niño event because an unusually large amount of heat has been absorbed in the tropical Pacific in recent years. Global warming plays a significant role here. As global warming progresses, the tropical Pacific continuously absorbs excess heat, which can be released during an El Niño event.
Variations in sea surface temperatures in the Pacific lead to droughts in Australia, floods in Central America and even temperature anomalies in Europe.Michael Mayer
What does the El Niño event mean for Europe?
Mayer: El Niño events have an impact on global atmospheric circulation, including Europe. However, atmospheric circulation over Europe is highly variable and it is therefore statistically difficult to establish a clear link with El Niño.
What we do know, however, is that the years following an event tend to be very warm globally. For 2027 we can therefore expect temperatures in Europe to be higher than usual. El Niño is a truly global climate phenomenon. It demonstrates that variations in sea surface temperatures in the Pacific lead to droughts in Australia, floods in Central America and even temperature anomalies in Europe.
The Atlantic is constantly in motion. But what if one of the most important ocean currents were to slow down?Susanna Winkelbauer
What is the AMOC?
Susanna Winkelbauer: The AMOC, the Atlantic Meridional Overturning Circulation, is a major circulation system in the Atlantic in which warm, salty water flows near the surface from south to north. In the North Atlantic, this water cools, becomes denser as a result and then sinks. At depth, the current then flows back southwards.
This entire circulation system is driven primarily by the temperature and salt content of the water. However, climate change is causing temperatures in the North Atlantic to rise and we are also seeing an increase in freshwater entering the ocean – for example, from the melting of the Greenland ice sheet or other glaciers or through increased precipitation. This makes the surface water less salty and lighter, so it cannot sink as easily – which in turn could cause the AMOC to weaken.
How close are we to the AMOC tipping point or collapse?
Winkelbauer: Internal mechanisms can cause this weakening to intensify further and further, which could then lead to what is known as a tipping point. This means that we would enter a state with much weaker currents, which would happen within a few decades. However, whether and when we will reach this tipping point is still relatively uncertain. There is a wide range of data: we have model data, proxy data and a wide variety of reconstructions, most of which point to a weakening. But the tipping point itself is still uncertain.
New model studies show that we can expect dry summers across large parts of Europe if the AMOC weakens significantly.Susanna Winkelbauer
What does a collapse of the AMOC mean?
Winkelbauer: If the AMOC weakens and transports less and less heat northwards, this will have a cooling effect in the north – across the North Atlantic and also across Europe, particularly in north-western Europe such as Scandinavia. However, we would also see an effect on precipitation, for example. New model studies show that we must expect dry summers across large parts of Europe if the AMOC weakens significantly. And we would feel the effects of that here in Austria too.