If global warming continues unchecked, summer monsoon rainfall in India will become stronger and more erratic. This is the central finding of an analysis that compared more than 30 state-of-the-art climate models from all around the world. The study, published today in Earth System Dynamics, predicts more extremely wet years in the future — with potentially grave consequences for the well-being, economy, and food systems of more than a billion people.
“For every degree Celsius of warming, monsoon rainfalls will likely increase by about 5%,” said lead author Anja Katzenberger from the Potsdam Institute for Climate Impact Research (PIK) and Ludwig-Maximilian University in Munich, Germany (LMU). She said that while the study confirms previous findings, the team’s analysis suggests that “global warming is increasing monsoon rainfall in India even more than previously thought. It is dominating monsoon dynamics in the 21st century.”
More rainfall is not necessarily a good thing for the farming sector in India and its neighboring countries, explained co-author Julia Pongratz from LMU. “Crops need water especially in the initial growing period, but too much rainfall during other growing states can harm plants — including rice on which the majority of India’s population is depending for sustenance. This makes the Indian economy and food system highly sensitive to volatile monsoon patterns.”
A look into the past underlines that human behavior is behind the intensification of rainfall. Starting in the 1950s, human-caused changes began to overtake the slow natural changes that occur over many millennia. At first, sunlight-blocking aerosols led to subdued warming and thus a decline in rainfall, but since then, from 1980 onwards, greenhouse gas-induced warming has become the deciding driver for stronger and more erratic monsoon seasons.
“We see more and more that climate change is about unpredictable weather extremes and their serious consequences,” said group leader and co-author Anders Levermann from PIK and Columbia University’s Lamont-Doherty Earth Observatory. “Because what is really on the line is the socio-economic well-being of the Indian subcontinent. A more chaotic monsoon season poses a threat to the agriculture and economy in the region and should be a wakeup call for policy makers to drastically cut greenhouse gas emissions worldwide.”
Adapted from a press release by the Potsdam Institute for Climate Impact Research