Frequently Asked Questions (FAQ)

Climatology | Impacts | Extremes| TCs affecting WA towns | Forecast Accuracy
Frequently Asked Questions | Annual summaries

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Climatology

6. Are we getting stronger and more frequent tropical cyclones in the last several years? What about climate change?

Trends in tropical cyclone activity in the Australian region (south of equator; 105-160°E) show that the total number of cyclones has decreased in recent decades (see graph). This decrease may partly be due to an improved discrimination between tropical cyclones and sub-cyclone intensity tropical lows. If weak cyclones are excluded from the analysis, the trend is more gradual and follows the downward trend in the Southern Oscillation Index suggesting that the decrease in cyclone numbers may be related to the greater number of El Niño events since the mid-1970s. However, the number of severe cyclones has increased and this does not appear to be due to improved discrimination between cyclones or trends in the Southern Oscillation Index. The actual cause of this is unknown.

According to the International Panel on Climate Change (IPCC) in the northern hemisphere, tropical cyclone activity has risen in the northwest Pacific and north Atlantic since 1950. However, there has been little change in the number of very strong typhoon-force or hurricane-force systems. There has been little change in the number of tropical cyclones in the north Indian Ocean, southwest Indian Ocean and southwest Pacific Ocean east of 160°E.

Despite advances in computer modelling of the global climate using various scenarios of greenhouse gas emissions, making projections of how tropical cyclones may change in frequency and intensity remains a significant challenge. Since tropical cyclone activity is modulated by the El Niño Southern Oscillation (ENSO), projections of cyclone frequency will partly depend on the projections of future ENSOs. It is uncertain how ENSO will change in a warmer world. Some studies have suggested that peak winds may increase by 5-10 % and peak rainfall rates may rise by 20-30 %.
For further discussion go to the US Atlantic Oceanographic and Meteorological Laboratory's Hurricane FAQ page.