Australia’s Bureau of Meteorology has officially declared 2020 a La Niña year. This irregular phenomenon interrupts Australia’s usual weather patterns. What will this year’s summer look like asks HDI Global’s Mr Stefan Feldmann?
Every language enthusiast will know ‘La Niña’ is Spanish for ‘girl’. And you’ve guessed right – its counterpart ‘El Niño’ means ‘boy’. Both words, however, are also used to describe weather phenomena. Both have their origins in the equatorial Pacific but can influence the weather worldwide. And both can have significant impacts on economies as they can intensify and prolong fire seasons, bring flooding and cyclones and therefore affect crop yields, corals, housing and infrastructure. With high values at stake, commercial insurers in particular keep a close eye on these weather phenomena.
What’s the weather like in usual years?
Typically, in the Pacific, trade winds drive warm surface water west. This transports humid air and precipitation to the east coast of Australia and Southeast Asia whilst cool water upwells off the Peruvian coast. During La Niña years these trade winds are amplified driving west even more warm surface water than normal. This leads to warmer than usual waters off Australia’s east coast and to increased convection.
At the same time the waters off the southern Pacific coast of South America cool down. The Bureau of Meteorology (BOM) calls this the cool phase of the El Niño Southern Oscillation (ENSO). “La Niña events often form in autumn or winter, then decay in late summer,” the meteorologists said. “The greatest impact normally occurs during the spring and early summer period.” La Niña also tends to ‘stick around’. The weather phenomenon typically lasts for around a year, but it can also be shorter, or much longer.
Organisations like Australia’s BOM or the US-weather agency NOAA determine a La Niña phase by observing ocean temperatures. Currently the central tropical Pacific Ocean is 0.8°C cooler than normal, and that has resulted in changes to trade winds and pressure patterns according to BOM. “Climate models suggest these patterns will continue until at least the end of the year,” the experts said.
What does this mean for Australia?
La Niña normally affects the eastern, central and northern regions of Australia. It brings more rain than in average years as well as cooler temperatures. “A positive could be a reduced bushfire risk due to the wetter conditions,” Willis Re Australia meteorologist and head of catastrophe analytics Michael Barkhausen said. “This might bring some welcome relief to Australia after the record bushfires last season.”
However, “Wetter weather potentially means more flood events that can cause damage to property and similarly the potential for more cyclones could also lead to more claims,” he said.
Historically, La Niña years tend to see more property claims than El Niño years owing to the impact of large flood, storm and cyclone events, the expert says adding that “this season, we have already seen a significant hail event impacting the area around Brisbane”.
The last La Niña event was recorded from 2010 to 2012. It resulted in one of Australia’s wettest two-year periods on record with widespread flooding in many parts of the country. Although tropical cyclone activity in the first year of the event was fairly average, the five tropical cyclones that did occur were in the severe category.
One example is the tropical cyclone Yasi, which caused widespread damage to far north Queensland. “The impacts of La Niña can vary significantly between events,” experts from BOM said. “It is likely this year will not see the same intensity as the 2010-11 La Niña event, but is still likely to be of moderate strength.”
Climate change comes into it as well
Research published by ARC Centre of Excellence for Climate System Science investigators in Geophysical Research Letters in 2018 found 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,” according to lead author Sarah Perry who at the time was a PHD student at the University of New South Wales.
For Australia, wet weather events can be expected to have greater and more intense rainfall according to Willis Re climate change expert and senior catastrophe and climate risk analyst Dr Andy Casely.
This means that this ‘supercharged wet weather’ will most likely go hand in hand with more flooding. “As warmer air can hold more moisture, when that rains out, it generates higher rainfall totals,” Dr Casely said.
Climate change will probably also make El Niño and La Niña events more intense in general. “For a country like Australia, where the see-saw between dry and wet extremes is often accentuated by the El Niño-Southern Oscillation processes, this will only enhance our already extreme weather, with more ‘extreme’ dry or wet seasons, rather than moderate ones,” he said.
Insurers heed these warnings and take them into account when calculating and pricing risk. They also play an increasingly important role in advising customers in terms of risk prevention and risk engineering. Insurers can provide ‘pricing signals’ – giving an indication where the public and private sectors as well as the consumers need to consider adaptation. A
Mr Stefan Feldmann is managing director for HDI Global in Australia.