In The News: El Niño

With an El Niño event now declared in the Pacific Ocean, we explore how research at the University has changed what we know about El Niño events since the last big one in 2015/2016.

Preparing for floods

Research carried out at the University has contributed to how the El Niño Southern Oscillation (ENSO) influences the likelihood of flooding in the Amazon basin, showing that only parts of the basin are affected. Our understanding of the importance of ENSO across Sub-Saharan Africa has been improved by looking at how the role of other modes of climate variability, such as the Indian Ocean Dipole, in driving flooding. In many parts of the world, seasonal hydrological forecasts produced by the Global Flood Awareness System (co-developed by researchers at the University) are able to provide more skillful predictions than knowledge of what has happened in past events.

Global Influence of ENSO

During strong El Niño events, the warmer atmosphere can hold as much as 300 cubic kilometres more water as invisible vapour (that’s the volume of 120 million Olympic swimming pools)! However, in the long-term, warming due to rising greenhouse gas levels is adding over 100 cubic kilometres of water to the atmosphere every decade. The strong 2015/16 El Niño was associated with very dry conditions over northern parts of South America, southern Africa and Australia and ongoing research suggests that this has sapped the ground of its water supply in places. The reverse happened in the strong La Niña of 2011 in which so much rain flooded into drylands, the sea level temporarily fell before this water found its way back into the water cycle.

Trends in ENSO

There have been an unusual number of La Niñas in the first decade of the 2000s as well as a very lengthy one recently (late 2020 to early 2023) and this unusual pattern of warming can affect clouds and how they influence global warming. Satellite observations and complex computer simulations show that the recent 2015/16 El Niño caused low altitude clouds to melt away in the parts of the Pacific and this resulted in more sunlight reaching the surface, adding to the warming effect.