Why are hurricanes like Milton in the US and cyclones in Australia becoming more intense and difficult to predict?

Tropical cyclones, known as hurricanes and typhoons in other parts of the world, have recently caused significant damage in many places. The United States was just hit by Hurricane Milton less than two weeks after Hurricane Helen. Climate change may have exacerbated the effects.

Tropical cyclone season (November to April) is approaching in Australia. The Japan Meteorological Agency released its long-term forecast for this season this week.

It forecasts that an average of 11 tropical cyclones could form in the region. Four planes are scheduled to cross the Australian coast. However, the risk of severe cyclones is higher than average.

So what do averages actually mean in a rapidly changing climate, and why is the risk of severe cyclones increasing?

The bureau’s projections are consistent with scientific evidence that suggests climate change is likely to reduce the number of tropical cyclones but make them more severe. Stronger winds, heavier rain and flooding are now likely.

Climate change is making predictions more difficult

Our knowledge of tropical cyclones and climate change is based on multiple lines of evidence around the world and in the Australian region. This research includes observational and modeling-based studies.

In recent years, the bureau’s seasonal outlook assumes that an average of 11 tropical cyclones will form in this region (covering the southern tropical region from 90 degrees east longitude to 160 degrees east longitude). Based on average values ​​for all years up to 1969.

However, for the past several decades, the annual average number of tropical cyclones has been less than nine. In the first decades, it was more than 12. This long-term downward trend makes seasonal predictions even more difficult.

The most recent above-average season (assuming an average of 11) was almost 20 years ago in the summer of 2005-2006, when 12 tropical cyclones formed. Since then, predictions for an above-average tropical cyclone season have not materialized.

The effects of El Niño and La Niña may also change.

Historical observations suggest that more tropical cyclones tend to form near Australia during La Niña events. This is the result of warmer and wetter water and air near Australia compared to El Niño events. The fluctuations between El Niño and La Niña conditions in the Pacific region are known as the El Niño Southern Oscillation (ENSO).

Such events can be predicted with useful accuracy, sometimes months in advance. For example, the National Oceanic and Atmospheric Administration (NOAA) predicts that “La Niña is likely to occur from September to November (71% chance) and is expected to last from January to March 2025.” I am doing it.

Based on this, one might expect more tropical cyclones to form in the Australian region than average. However, the influence of ENSO on tropical cyclones has weakened in our region. This is another factor that makes long-term forecasts difficult.

Compared to NOAA’s La Niña leaning, the agency’s ENSO outlook is somewhat closer to a neutral ENSO situation based on its modeling. “Even if La Niña does occur in the coming months, it is expected to be relatively weak and short-lived,” the agency said.

The agency’s forecast for the average number of tropical cyclones this season is broadly consistent with predictions for near-average ENSO conditions.

So what does this mean for this cyclone season?

If the current climate results in an average season for Australia, this could actually mean fewer tropical cyclones than the historical average. This number may be closer to 8 or 9 than 11 or 12 (values ​​higher or lower than this range are also possible).

However, if it forms, it is likely to become a Category 4 or 5 tropical cyclone. These are windy, typically with gusts exceeding 225km/h, and are likely to cause severe flooding and coastal damage.

If we end up exceeding the recent average of eight to nine tropical cyclones, which could occur if NOAA-predicted La Niña conditions materialize, the risk of impact increases. However, there is one piece of partially good news regarding climate change in this context, given that La Niña events have a smaller impact on increased tropical cyclone activity than before.

Another factor is that the world’s oceans are much warmer than normal. Warm ocean water is one of several factors that provides the energy needed for tropical cyclone formation.

Recently, many ocean heat records have been set. This means we are in “uncharted territory” from a temperature perspective. Relying on what happened in the past when predicting the current climate creates even more uncertainty.

Latest evidence is essential as climate changes

Science makes clear that we need to plan for the impact of tropical cyclones differently than what may have worked in the past. This includes preparing for the possibility that, while the overall occurrence of tropical cyclones may decrease, they are more likely to cause more damage when they do occur. This means an increased risk of wind damage, flooding and coastal erosion.

Seasonal forecast guidance can be used as part of planning improvements. Strengthening design standards and other climate change adaptation activities are also needed. Everything can be updated regularly to stay consistent with the best available scientific knowledge.

Increased preparedness is more important than ever to reduce the likelihood of disasters caused by tropical cyclones in the current and future climate.

This article is republished from The Conversation under a Creative Commons license. Read the original article.