Written by Laure Poncet
In a recent study, climate scientists have shown that El Niño-Southern Oscillation (ENSO) teleconnections may amplify with climate change, leading to more severe temperature and precipitation extremes globally.
ENSO is a natural phenomenon associated with changes in sea surface temperatures in the central and eastern tropical Pacific. Through remote impacts known as teleconnections, ENSO influences temperature and precipitation patterns around the world.
While it has been suggested that ENSO teleconnections will amplify with climate change, potentially altering global temperature and precipitation patterns, it remains unclear how these amplifications will impact precipitation and temperature extremes globally.
Ruby Lieber, a PhD student at the University of Melbourne and lead author of the study, said:
“Many studies have analysed ENSO teleconnections with mean temperature and precipitation patterns, but there have been only a few teleconnections studies examining the influence on extremes. Our new study aims to address this research gap.”
“We show that ENSO teleconnections will likely amplify under future warming, leading to an amplification in the intensity of precipitation and temperature extremes.”
“This could have devastating consequences for regions that already experience damaging extremes during ENSO events.”
What are ENSO teleconnections?
ENSO is a climate pattern associated with changes in sea surface temperatures in the central and eastern tropical Pacific Ocean. It comprises two active phases, El Niño and La Niña, as well as a neutral phase when neither El Niño or La Niña occurs.
During an El Niño phase, temperatures in the central and eastern tropical Pacific are warmer than average, while they are cooler than average in a La Niña phase. This variability can significantly influence climate and weather around the world.
“ENSO influences climate and weather far beyond the tropical Pacific region where it originates,” said Lieber.
“We refer to these remote influences as teleconnections. ENSO teleconnections can affect temperature and precipitation patterns globally, as well as storm tracks and extreme climate events. This in turn can impact our ecosystems, agriculture and economies.”
In terms of temperature and precipitation patterns, El Niño is usually associated with above average global mean surface temperature and can greatly influence drought conditions across the world (Figure 1). Conversely, La Niña usually brings cooler global average temperatures and can lead to floods in various regions (Figure 2). Note that this is not a general rule and some regions can experience the opposite effects. For example, California is more prone to increased precipitation and flooding during El Niño (Figure 1) and reduced rainfall and increased risk of drought during La Niña (Figure 2).
Figure 1: El Niño precipitation teleconnections. Source: International Research Institute for Climate and Society.
Figure 2: La Niña precipitation teleconnections. Source: International Research Institute for Climate and Society.
ENSO temperature and precipitation teleconnections are most pronounced in parts of Australia, North America, South America and Africa. In Australia, El Niño is typically associated with reduced rainfall in the southeastern part of the country, while La Niña typically brings above-average rainfall.
It has been suggested that ENSO teleconnections will intensify in the future in response to climate change and continued warming. An international team of researchers has found that approximately 50% of the global land areas will experience a change in the strength of temperature and precipitation teleconnections, with most impacted regions experiencing an amplification rather than a dampening1.
ENSO and climate extremes
Many of the most devastating impacts of ENSO are felt through extremes. Extremes are defined as statistically rare events. For instance, in climate data, extremes can be unusually high or low temperatures.
ENSO has been shown to influence both temperature and precipitation extremes globally. For instance, ENSO has been linked to extreme rainfall and extreme temperature in Argentina. In North America, developing La Niña events are associated with more summer heat extremes and drought in the Southeast. In Australia, El Niño is usually associated with droughts in the southern and eastern regions, while La Niña is associated with extreme rainfall in the northern part of the country.
It has been suggested that ENSO teleconnections may amplify in the future. Yet, it remains unclear how these amplifications would translate to extremes.
Drought in Australia. Istock
The study’s findings
Addressing this research gap, Lieber and her co-authors have investigated how ENSO temperature and precipitation teleconnections will change with future warming and what this would mean for extremes. Here are some of their findings.
Changes in temperature and precipitation teleconnections
Using climate model simulations, the team of researchers first examined how ENSO temperature and precipitation teleconnections may change under a future warming scenario with very high greenhouse gas emissions.
For both El Niño and La Niña phases, temperature teleconnections were found to amplify in Southeast Asia, northern South America, northern Africa, and over most of Australia. Precipitation teleconnections intensified over northern Australia, East Africa and parts of Southeast Asia and South America.
Dampening of ENSO teleconnections were also found in Central America and over parts of North America.
“Our findings show that more regions may experience an amplification of ENSO temperature and precipitation teleconnections rather than a dampening.”
“An amplification means that regions that are already experiencing warm or cold anomalies during an El Niño or La Niña phase could get even warmer or colder in the future.”
“Similarly, regions that are already experiencing dry or wet conditions could become even drier or wetter with the amplification of ENSO teleconnections.”
Changes in ENSO teleconnections with extremes
The researchers then investigated whether the same evolution would apply to extremes.
They found that the response of ENSO teleconnections with extremes was very similar to the mean response.
“We found that ENSO-induced extreme rainfall and temperatures will generally amplify in the same regions as ENSO teleconnections with mean temperature and precipitation.”
“This means that regions that are predicted to experience an amplification of ENSO teleconnections in the future could also expect a comparable amplification in the intensity of temperature and precipitation extremes.”
“This could have devastating impacts for regions already experiencing damaging extremes under El Niño and La Niña events, such as South America and Australia.”
A worrying picture of future extremes
This study demonstrated ENSO teleconnections may amplify in the future, leading to more severe ENSO-driven precipitation and temperature extremes in some parts of the world.
With climate change, precipitation and temperature extremes are expected to worsen. This study highlights how an amplification in ENSO-induced extremes could exacerbate this trend.
“As extreme precipitation is expected to intensify with climate change, ENSO may further enhance this. The same is true for extreme temperatures, which are expected to intensify as the climate warms.”
“Given the impacts of extremes, particularly in more vulnerable regions, this is one of many incentives to limit global warming through reduced greenhouse gas emissions.”
The study will be published in the Journal of Climate. An early online release is available here. The was authored by Ruby Lieber, Dr. Josephine Brown, and Dr Andrew King from the ARC Centre of Excellence for Climate Extremes, and Dr. Mandy Freud from CSIRO.
References
- McGregor, S., Cassou, C., Kosaka, Y., & Phillips, A. S. (2022). Projected ENSO teleconnection changes in CMIP6. Geophysical Research Letters, 49 (11), e2021GL097511.