The Bureau of Meteorology (BOM) has officially declared the arrival of two significant climate drivers in Australia: El Niño and a "positive" Indian Ocean Dipole (IOD). 

This double whammy spells trouble, with extreme heat looming over the country this spring and summer.

After much anticipation, BOM has confirmed that the influential El Niño weather pattern has returned, marking its first appearance in eight years. Simultaneously, the less-known positive IOD has also formed.

These two climate events signal a hot and dry remainder of 2023, particularly in the eastern states. 

Climate experts caution that, combined with the ongoing effects of climate change, Australia is bracing for a scorching summer.

Karl Braganza, BOM's head of climate monitoring, says that when El Niño and a positive IOD occur in tandem, rainfall deficits worsen, leading to heightened fire danger and scorching temperatures.

With an established El Niño and positive IOD, the predictions for warm and dry conditions gain more certainty, potentially lasting into autumn.

The combination of these climate drivers increases the risk of extreme heatwaves and elevated fire danger in southeastern Australia.

BOM's El Niño declaration was made when three of four criteria were met, including a consistent atmospheric response above the tropical Pacific.

It is essential to remember that while two-thirds of Australia's driest years coincide with El Niño, each event is unique. 

El Niño is part of a natural climate cycle, typically occurring every three to five years.

Catherine Ganter, Bureau Senior Climatologist, says the substantial influence of a positive IOD on Australia's rainfall and temperature is like mirroring the impact of El Niño.

Historically, Australia has experienced 16 positive IOD and 15 El Niño years since 1960, with seven of those years featuring both events simultaneously.

The timing of this declaration coincides with parts of New South Wales facing catastrophic fire danger due to intense winds and unseasonably hot temperatures in the southeast.

El Niño is a typically long-lasting event, spanning from nine months to a year, resulting in reduced rainfall, increased temperatures, and drought, primarily affecting Queensland and New South Wales.

Additionally, El Niño can bring more extreme heat, frost risks, fewer warm spells, reduced snowfall, and late monsoons to various parts of Australia. However, the specific outcomes depend on multiple factors.

The positive IOD is less renowned but can have a substantial dry impact in Australia, particularly in the cooler months. 

It played a role in the severe bushfires of 2019-20. When El Niño and a positive IOD overlap, their dry effects compound, although this does not always lead to dire consequences.

Despite the potential for a powerful El Niño this year, its impact on Australia remains uncertain. 

While this summer might not be a repeat of the catastrophic 2019-20 bushfire season, authorities caution that vigilance and preparedness are still paramount, regardless of climate conditions.