Climate change supercharged Cyclone Gabrielle. By how much remains unknown
Scientists have cautiously concluded climate change is partly responsible for Cyclone Gabrielles damage . The February disaster featured many of the effects of a heating atmosphere souped-up storms, extreme rain, flooding and intense winds. Dubbed the countrys most severe weather event this century , the ex-tropical cyclone caused billions of dollars of damage plus a spike in public concern about climate change. But climate scientists are more cautious, turning to weather data and computer models before making an official conclusion about the role of the heating planet in the disaster. READ MORE: * 'Staggering amount' of rain fell during Cyclone Gabrielle, fresh data shows * Family of eight living in their kohanga after Cyclone Gabrielle * Cracking the code of catastrophic floods in New Zealand * What does cyclone damage mean for our food supplies? Weather records suggest climate change is responsible for between 20% and 30% of the rain that fell in Hawkes Bay and Tairawhiti, according to an international research team. Yet, climate simulations arent coming to the same conclusion. While the cyclone affected much of the North Island, Hawkes Bay and Tairawhiti recorded particularly high rainfall. One site in Hawkes Bay weather station recorded nearly half a metre of rain 493mm over two days. A Gisborne station recorded even more: 621mm over 48 hours. The team compared the two regions figures against the last 44 years of two-day rain records, Niwa climate scientist Sam Dean said. By heating the Earth by roughly 1.2C, humanity made the regional rainfall 20 to 30% more intense and three to four times more likely to occur, the statistical analysis found. The team isnt particularly confident in the figures, however. In addition, the modelling work failed to back the analysis up, Dean said. It doesnt change our advice that climate change is a serious concern. Researchers recreated Cyclone Gabrielle within computer-modelled worlds where humanity had never emitted greenhouse gas. To be included in this study, models needed to have a good representation of the New Zealand countryside, said University of Waikato climate scientist Luke Harrington. The models also needed to put the simulated cyclone on its correct track: hitting the East Coast hard. Some [models] showed small increases in the frequency and intensity of Gabrielle-like rainfall. But most did not, Harrington added. Dean said the conflicting results are not especially surprising at an early point in the research. Either the observations are just a bit of an anomaly, the models arent quite good enough for such a small region or most likely we need to do the analysis over a much longer period of time, he added. The team part of the international World Weather Attribution group aimed to share the initial findings quickly, Dean said. As we do further research, we may have more to say. Even so, the team is confident on the overall evidence to conclude climate change made Gabrielle wetter and more intense. But the exact percentage is still up for debate. These are gigantic amounts of rainfall, Dean said. I have no doubt whatsoever in my mind and across my experience as a climate scientist that climate change has influenced that event. Friederike Otto, of Imperial College London, said this type of work highlights that climate change is not a future issue. It affects people particularly vulnerable populations everywhere around the world today. Gabrielle was Aotearoas second cyclone of 2023, the team noted. Cyclone Hale may have left soils soggy and more vulnerable to slips when Gabrielle arrived. On the positive side, New Zealand is well-connected. Weather warnings are typically received by at-risk communities allowing them to prepare. Yet repeated weather events may have caused disaster fatigue, where people failed to heed warnings. Dean said the extent of the cyclones damage plus how it has affected and disrupted peoples lives was shocking. The researchers hoped to complete a broader study looking at wind and storm surges, as well rainfall. Our weekly email newsletter, by the Forever Project's Olivia Wannan, rounds up the latest climate events. Sign up here .