Australia, South America and Equatorial Africa are in the firing line for more extreme weather, as global warming looks set to increase the area of land affected by El Niño-Southern Oscillation (ENSO), better known as El Niño and La Niña events.
ENSO events already have significant impacts on economies, affecting fire seasons, flooding, crop yields, cyclone activity, coral bleaching and infrastructure.
New research published by ARC Centre of Excellence for Climate System Science investigators in Geophysical Research Letters, finds global warming could cause a 20% increase in the areas impacted by temperatures changes and extremes during ENSO events and a 10% increase in the areas impacted by precipitation changes during ENSO events.
Models suggest that most of these changes would occur in just three areas (Australia, South America and Equatorial Africa), although precipitation changes could also occur in northeast United States and across the Maritime Continent to the north of Australia.
“Previous research strongly suggested the atmospheric response to ENSO would intensify over the tropical ocean as the world warmed,” said lead author and PhD student from the University of New South Wales Sarah Perry.
“Our new work suggests that in the future we will not only see an increase in the intensity of ENSO impacts over the ocean, but these impacts of La Niña and El Niño would be felt over a more extensive area of land, including over Australia, South America and Africa.”
The global study compared two 50-year periods simulated with 40 climate models to get its results. The first period (1953-2002) overlapped with observations, which were also used to test the models’ skill in simulating ENSO impacts. It then compared these with climate model projections for the period 2040-2089 under a business as usual scenario (RCP 8.5).
The key difference between the two periods was warmer background sea surface temperatures. This warming allows strong convection over the tropical Pacific Ocean to form more easily during ENSO events, which intensifies and expands existing atmospheric connections.
“This is a classic example of how changes to climate in one area can affect areas half a world away, although the next big question is whether climate change may bring ENSO impacts to entirely new regions,” said fellow author Dr Shayne McGregor from Monash University.
“It is quite possible that ENSO impacts will not simply expand and intensify the current connections but could also form new atmospheric connections bringing ENSOs impacts to places that have never before been affected.”
- Perry, S. J., McGregor, S., Gupta, A. S., & England, M. H. (2017). Future changes to El Niño–Southern Oscillation temperature and precipitation teleconnections. Geophysical Research Letters, 44, 10,608–10,616. https://doi.org/10.1002/2017GL074509