An international team of scientists led by the University of Newcastle has identified a growing frequency of intense rainstorms in Australia over the past 50 years. The researchers have found that short yet powerful storms are strengthening faster than what was expected with global warming, and the experts say that this will lead to increased flash flooding.
The investigation was focused on daily and hourly rainfall extremes between 1966-1989 and 1990-2013, which were collected from 107 weather stations across Australia.
The study revealed that the amount of water falling in hourly storms such as thunderstorms is increasing at a rate that is two to three times higher than what was anticipated with climate change. The largest increases in rainfall have occurred during the most extreme events.
“It was thought there was a limit on how much more rain could fall during these extreme events as a result of rising temperatures,” said study lead author Dr. Selma Guerreiro.
“Now that upper limit has been broken, and instead we are seeing increases in rainfall, two to three times higher than expected during these short, intense rainstorms.”
“This does not mean that we will see this rate of increase everywhere. But the important thing now is to understand why rainfall is becoming so much more intense in Australia and to look at changes in other places around the world. How these rainfall events will change in the future will vary from place to place and depend on local conditions besides temperature increases.”
The research suggests that short, intense rainstorms may be underestimated due to the frequency and severity of flooding that can result from them.
“These changes are well above what engineers currently take into account when determining Australia’s flood planning levels or designing stormwater management and flood defence infrastructure,” said study co-author Professor Seth Westra.
“If we keep seeing this rate of change, we risk committing future generations to levels of flood risk that are unacceptable by today’s standards.”
The research has demonstrated that extreme hourly rainfall cannot be predicted based on temperature alone because many other atmospheric changes also play a role in these complex events.
The study is published in the journal Nature Climate Change.