Global warming creating new weather patterns leading to floods, heatwaves: Study

Bengaluru: Global warming, along with other factors of climate change, are leading to an increased frequency of new set of weather patterns associated with floods and heatwaves in the Indo-Pacific, including south India, while some patterns that were once prominent were seen "disappearing" rapidly in the last 83 years, a new study by international scientists published in Nature Geoscience.

Led by Chenyu Dong and assistant professor Gianmarco Mengaldo from National University of Singapore, the study was the result of collaboration from University of Cambridge (UK), Stockholm University (Sweden), Columbia University (US) and others besides the World Meteorological Organisation.

Till now, studies have largely focussed on the shifts in average regional weather patterns but have not been able to identify trends of for each daily weather pattern. The new study enables "a direct study of their (weather patterns') association with extreme events".

Researchers quantified weather patterns in 83 years (1940-2022) and identified sets of weather patterns similar to each other ("analogues"). The data was then divided into nine periods of equal duration to calculate the number of analogues.

The new weather patterns were clustered within the past 20-30 years, with an increasing trend of 11 analogues per decade. On the other hand, the once prominent patterns, clustered in the period 1940-1970, were decreasing rapidly at 15 analogues per decade.

The researchers found that the emerging patterns could not be explained by existing natural variabilities like El Nino, the Indian Ocean Dipole and others. They found the changes linked to shifts in the Pacific Walker Circulation (the winds that move water and air to the western pacific ocean towards Bay of Bengal), a key driver of tropical weather and climate, whose future changes remain highly uncertain in the current climate models that are "unable to capture" the strengthening of PWC in recent decades.

NUS Assistant Professor Mengaldo said critical changes in tropical weather patterns were significantly aggravating extremes like heatwaves and extreme precipitation in the tropical Indo-Pacific region. "We show that the changes identified cannot be fully explained by interannual modes of variability, and a possible culprit is anthropogenic global warming, though the influence of other factors may play a role," he said.

Mengaldo said more research was required to better inform climate modelling and climate adaptation strategies, especially in the tropical Indo-Pacific, where climate models still struggle to provide reliable projections. "For Singapore, and other countries in Southeast Asia, improving climate projection capabilities and better understanding how tropical dynamics and regional extremes are evolving is of vital importance. This study is one step towards this direction,” he added.