Future warming will affect the influence of the El Niño – Southern Oscillation

September 14, 2022

Australia is about to head into its third consecutive La Niña increasing flood risk across much of the country. Under our changing climate new research has shown that ENSO could drive more extreme dry and wet conditions globally.

El Niño-Southern Oscillation (ENSO) is an important driver of Australia’s climate. ENSO describes variations between warm (El Niño) and cool (La Niña) phases of sea surface temperatures in the central and eastern equatorial Pacific and overlying changes in the atmospheric circulation. The climatic impacts of ENSO extend worldwide, making it an important driver of global interannual climate variability.

Climate drivers like ENSO impact our weather over days and seasons. Weather at one location is often linked to the weather at other, often very distant, places around the world. These large distance atmospheric linkages are called ‘teleconnections’. ENSO has well-known teleconnections with sea surface temperature in the central equatorial Pacific Ocean associated with massive changes in weather across the globe, from Peru to North America and East Africa.

In Australia, the effects of ENSO are present across most of the country, especially in the north and east. ENSO-related droughts, bushfires and floods significantly affect the Australian economy and community. Understanding whether ENSO’s teleconnections may change under a warming climate provides critical information to support evidence-based climate adaptation and decision-making.

Using the latest climate models Climate Systems Hub researcher, Dr Shayne McGregor from Monash University, led research that compared historical ENSO surface temperature and precipitation teleconnections with those under a future high emission scenario. The analysis used simulations from more than 30 models from the latest generation of global climate models, CMIP6. It focused on summer in Australia, when ENSO typically peaks.

Changes in ENSO teleconnections are projected under a warmer future

Dr McGregor and his team found significant surface temperature and precipitation teleconnection changes over approximately half of the regions studied for the 2081-2100 period under high future emissions compared to 1950-2014.

The changes in ENSO teleconnections occurred across all emissions scenarios, but the changes and number of regions displaying these changes varied with emissions scenario. ENSO precipitation and surface temperature teleconnection changes will be larger and impact more regions if more future warming occurs, and smaller impacting less regions if projected future warming is reduced.

Meaning that every degree of warming counts- a larger proportion of precipitation and surface temperature teleconnection changes occurred under a high emission scenario than under a low emission one.

‘This study is a timely reminder of the need to act now to reduce greenhouse gas emissions’, says lead researcher Dr Shayne McGregor.

‘Lowering greenhouse gas emissions as quickly as possible may help to avoid the projected amplification of ENSO teleconnection changes – and the possible associated amplification in extreme weather events.’

For the changes in ENSO teleconnections projected under a high emissions future, researchers found that most will result in a strengthening of these changes. That is, there will be even stronger linkages between ENSO-related climatic changes in many areas. This may mean that the impacts of ENSO on the climate will be stronger in the future.

Supporting action on climate change

Previous research suggests that ENSO influences the frequency of floods, bushfires, and drought in Australia. Thus, an amplification of ENSO teleconnection changes may result in associated increases in these events.

Models projected significant ENSO teleconnection changes for 2081-2100 relative to 1950-2014. Many of these changes suggest that amplification of historical ENSO teleconnections will occur in the future under a changing climate. However, some regions display a significant teleconnection dampening.

The smaller teleconnection changes projected for low emissions scenarios and the scaling of teleconnection changes with projected warming levels suggests that many of the future changes to ENSO teleconnections can be avoided by mitigating future warming.

Read the full article here


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