Typhoon Shanshan made 7.5% more intense and 26% more likely by climate change


Typhoon Shanshan made landfall in southwestern Japan on 29th August 2024, lashing the country with torrential rain and strong winds. 

Using an innovative attribution method, climate scientists quantified the influence of climate change on Typhoon Shanshan's powerful winds that affected Japan’s southern island, Kyushu. The Imperial College Storm Model (IRIS) analysed synthetic storm tracks to determine what the intensity and likelihood of typhoons like Shanshan would be without 1.3°C cooler world to understand changes due to human-caused climate change.

Using IRIS, thousands of typhoons close to Kyushu were simulated (Figure 2), allowing the scientists to calculate a range of possible intensities in both a pre-industrial colder world or our current climate with 1.3°C of warming. 

The study looked at potential intensity (Figure 1) and found that the maximum wind speeds of typhoons like Shanshan have become about 6.5 mph or 7.5% more intense due to climate change. This metric uses sea surface and air temperature, alongside air humidity data, to predict maximum typhoon wind speed. 

The IRIS model also found that devastating typhoons like Shanshan have become 26% more likely due to climate change (Figure 3). In other words, with 1.3°C of warming, the expected frequency of conditions similar to Typhoon Shanshan has risen from around 4.5 times per decade to 5.7 times per decade.  

Figure 1 - Estimated zonally-averaged change in August potential intensity from pre-industrial to present day expressed in terms of typhoon sustained maximum wind speed.

Figure 2 - Events contributing to the attribution analysis. Black circles show the location of the maximum intensity of tracks of observed typhoons in the vicinity of Kyushu.  Blue dots show the same for a sample of tracks simulated by IRIS. The black line shows the observed path of Typhoon Shanshan.

Figure 3 - Return curves for hurricanes passing close to Kyushu. IRIS pre-industrial and present-day simulations shown in blue and orange respectively, observations are in black (1980-2023). The shading shows range of sampling uncertainty of 44-year samples of IRIS simulations.

The return period (RP) is the expected interval between events which exceed the return value, Vmax, the typhoon sustained maximum wind speed. FAR is the fractional attributable risk and equals to 1-(RP 2024/ RP pre-ind).