In Australia, droughts and bushfires are becoming increasingly frequent. This pattern is similar to what I observed while doing research in southern California, which is also experiencing more wildfires and droughts. However, Australia also sees the other extreme. Floods have become more frequent and severe in many parts of the country. This change is similar to what I experienced back home in Florida, where sea levels are rising and more severe hurricanes have also contributed to flooding.
While having both droughts and floods might seem unusual, this contrast is typical of many areas in Australia. These extremes are driven by the El Niño Southern Oscillation (ENSO), a cycle in which trade winds, which blow over the equator, change in their strength or direction over the Pacific Ocean. Trade winds usually move from west to east, but El Niño years occur when they weaken and/or shift direction towards the west. El Niño years are associated with major changes in weather patterns across the globe. In Australia, El Niño years are typically dry and fire-prone. Eventually the Atlantic Ocean currents switch back to their usual west to east direction, but they are stronger than usual. These periods are referred to as La Niña, and they also lead to changes in weather patterns worldwide. La Niña years are characterized by more rain and flooding in Australia.
Climate change has led to increasing unpredictability of El Niño and La Niña, which also makes it hard to predict when associated weather patterns will occur and how intense they will be. In recent years, we’ve experienced stronger and more long-lasting ENSO cycles. The 2018-19 bushfires, which were some of the most intense wildfires in recent Australian history, occurred during an El Niño period.
