Earth Sciences NZ and Waikato University researchers predict even heavier falls of rain in cyclonic storm events like Gabrielle in future years due to global warming.
Earth Sciences NZ and Waikato University researchers predict even heavier falls of rain in cyclonic storm events like Gabrielle in future years due to global warming.
The amount of rainfall in tropical cyclones is expected to significantly increase across the southwest Pacific, including New Zealand, because of global warming, says Earth Sciences New Zealand.
Researchers from Earth Sciences New Zealand (the recently merged GNS and Niwa) and the University of Waikato, using high-resolution modelling, predict rainfallfrom cyclones could rise by up to 35%.
Researchers used the latest climate change projections released last year by Niwa with the Ministry for the Environment, Earth Sciences NZ said in a release.
Cyclone Gabrielle caused millions of dollars in damage across the region.
Study lead and climate scientist Dr Peter Gibson said they simulated more than 1800 years of data from different climate models and levels of greenhouse gas emissions.
“We wanted to assess how the frequency and severity of tropical cyclones in the southwest Pacific may change by the end of the century.
“Under the full range of climate scenarios examined, there was an increase in tropical cyclone rainfall. This was proportional to the rate of emissions, with the most pronounced rise in extreme rainfall occurring under the highest emissions,” Gibson said.
“If that scenario plays out, we can expect around 30-35% more extreme rainfall during tropical cyclones than we experience today.
“Even under the best-case scenario, we will still see an increase proportional to the warming experienced.
“Extreme wind speeds are also likely to increase, but not to the same extent.”
Future cyclonic storm events across the country will bring heavier falls of rain, Earth Sciences NZ says.
Gibson said the more greenhouse gases emitted, the higher temperatures would get, with a high emissions scenario representing around a 3C increase by the end of the century.
“A warmer atmosphere holds more water, so when storms develop they have access to more water vapour that can be released as heavier rainfall.
“While the model simulations didn’t show an overall increase in the total number of cyclones by the end of the century, there is compelling evidence that the strongest (Category 4 and above) will become more frequent.”
One or two ex-tropical cyclones typically affect New Zealand each year.
“However, it’s the really big, much rarer events that cause the most damage.
“The difference between a river flooding or not can often be small, so any increase in rainfall is significant and potentially very impactful,” Gibson said.
The February 2023 Cyclone Gabrielle, which at its peak reached Category 3, and the Auckland Anniversary weekend event, resulted in total estimated costs of $14.5 billion.
“More research is being undertaken by Earth Sciences NZ into specific weather and climate hazards in the projections to provide clarity on the future climate New Zealanders are likely to face in the decades to come.”
