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Some of the world’s most intense thunderstorms occur in the tropics and subtropics but until now the relationship between such storms and climate change has been uncertain.
A new analysis of climate-change predictions suggests that the frequency of severe thunderstorms is likely to increase as the planet warms in tropical and subtropical regions.
The analysis is part of a study led by a Monash researcher Martin Singh, and published in the prestigious Proceedings of the National Academy of Sciences (PNAS) journal.
“The question of whether the frequency of severe thunderstorms would increase as the planet warms has always been challenging,” said Dr Singh, from the Monash School of Earth, Atmosphere and Environment.
“It is challenging because our tools - global climate models –are not detailed enough to analyse individual thunderstorms.
“But in our study we changed tactics and instead used global climate models to predict changes in the potential energy available to thunderstorms in response to rising greenhouse-gas concentrations.”
The researchers found that the average amount of potential energy available on the highest-energy days was likely to increase over time in the tropics and subtropics.
“We also show that an important process that allows this potential energy to build up in the atmosphere is related to the mixing of air between clouds and their environment,” Dr Singh said.
As the climate warms, this mixing mechanism becomes more efficient in generating potential energy, accounting for the increase seen in climate-model predictions.
The mixing hypothesis also suggests that the highest values of potential energy occur on days when the humidity of the atmosphere is relatively low, and this was the case in observations of the tropical and subtropical atmosphere.
“Our predictions suggest that the frequency of conditions favourable to severe thunderstorms will increase markedly as the climate warms,” Dr Singh said.
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Professor Jean Palutikof is Director of the National Climate Change Adaptation Research Facility at Griffith University
The suggestion from climate models that destructive thunderstorms with the potential to cause bushfires may become more common is concerning.
With the recent events in California, and the Black Saturday bushfires here in Australia in 2009, we have seen how even the most developed countries can suffer catastrophic damage and loss of life in bushfires.
Recent interest in Indigenous approaches to bushfire management, emphasising regular 'cool burn' patch burning, is timely. These approaches may offer effective control mechanisms as the risk of bushfires grows under a warmer climate.
Professor Steven Sherwood is ARC Laureate Fellow at the ARC Centre for Climate System Science and UNSW Climate Change Research Centre and Chief Investigator at the ARC Centre of Excellence for 21st Century Weather
It seems that every few months brings news of an unprecedented inundation somewhere in the world, and global observations indeed tend to show a systematic increasing trend in peak rain rates that implies not only a moister atmosphere but also strengthening storms. This new study adds another piece to the puzzle of why this is happening.
Since the late 1980s we’ve had a theory for predicting the peak strength of tropical cyclones, which says their energy content should increase by about 7 per cent per degree C of warming, but that theory applied only to the most extreme cyclones. The new Singh et al. study confirms a similar, but much newer theory for more common storm activity, which predicts a similar intensification. Both theories ultimately trace the intensity increase to increases in the moisture-holding capacity of a warmer atmosphere.
So the bottom line is that our understanding is getting better, and continues to point to more intense storms and peak rains as climate warms. The results would apply everywhere, including Australia. This study did not look at specific regions, but another study published earlier this year (Bao et al.*) examining Australia specifically found that the most extreme rains are expected to intensify nearly everywhere, even if average surface climate stays the same or becomes drier; a similar results was also published this year for the continental US**.
*'Future increases in extreme precipitation exceed observed scaling rates', Bao et al, Nature Climate Change, 2017, doi:10.1038/nclimate3201
**'The future intensification of hourly precipitation extremes', Prein et al, Nature Climate Change, 2017, doi:10.1038/nclimate3618
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