NEW DELHI: From Houston all the way to Mumbai and from Nepal to the desert state of Rajasthan , rains have cut a swathe of destruction with flooded streets and thousands marooned as their cities and villages go under.With people across the globe dealing with the humanitarian and economic fallout of unusually heavy rains this year, are extreme weather events the new normal?Scientists, meteorologists and climate change experts blame rising global temperatures for the erratic weather patterns, leading to instances like heavy rains and floods.Heavy rainfall, cloudbursts, thunderstorms and heat waves are indeed becoming the new normal, said former India Meteorological Department (IMD) director general Laxman Singh Rathore.A worrying trend, added the consultant with the World Bank for South Asia on Climate Change, was that "periodicity and severity" had increased."In case of rainfall, the average precipitation has more or less remained the same, the dry spells have increased but the amount of rainfall remains the same. This means there is heavy concentration of rainfall over a particular region while other areas go dry," explained Jatin Singh, CEO of Skymet, a private weather forecasting agency.IMD recorded 2016 as the hottest year since 1901. And, according to the Intergovernmental Panel on Climate Change (IPCC) fifth assessment report on climate change, observations since 1950 show changes in some extreme events, particularly daily temperature extremes and heat waves.The IPCC report also noted that it is likely that the frequency of heavy precipitation will increase in the 21st century over many regions.The numbers are alarming.According to the United Nations Office for Coordination of Humanitarian Affairs (OCHA), 41 million people have been affected due to torrential rains in India, Nepal and Bangladesh this year.Nearly 900 people have died in the three countries, a report on the UN news website said.An IMD report added that 1,600 people in India died due to extreme heatwave conditions which 475 lives were lost in floods and thunderstorms in 2016.Rathore said South Asian countries have been affected due to torrential rains and floods because of high population density.But how does global warming lead to heavy rainfall?Roxy Mathew Koll, a scientist researching climate change with the Indian Institute of Tropical Meteorology, Pune, a premium institute under the Ministry of Earth Sciences , explained that the atmosphere and the oceans were getting warmer due to increasing carbon dioxide, a result of human activities."A warmer atmosphere holds more moisture. This results in two factors. The first is that warm moist air is lighter than cold dry air and hence makes the atmosphere unstable as it rises up," said Koll.The second factor, he added, is that since the atmosphere holds more moisture, it dumps it all together -- a heavy rainfall event.These factors leads to erratic weather, including extreme rainfall events across the globe.There are domestic factors, too, that aggravate losses in times of extreme weather.Former IMD DG Rathore pointed out that in case of cities, natural drainage systems have been "altered" at the cost of infrastructure development.One major reason for the 2005 Mumbai deluge, in which more than 500 people were killed with 944 mm of rain in a single day, was the damage done to natural drainage systems like the Mithi river. The river, which runs through the suburbs, has been revived to some extent now.Vineet Kumar, programme officer (Climate Change) with the Centre for Science and Environment ( CSE ), said research on climate change and its effects was insufficient for exigency plans at the micro-level."Due to this, there is a huge gap in planning a policy to deal with the problems occurring due to climate change. For instance, there are not enough studies on the adverse impact on crops due to this phenomenon to come up with a policy on how to deal with it," Kumar said.As states like Bihar count their dead -- an estimated 500 killed in the floods this year alone -- and Mumbai gets back on its feet after the heavy rains yesterday, the hope is that next year will be different.