Global warming makes Indian summer monsoon rainfall more erratic

If global warming continues unchecked, summer monsoon rainfall in India will become stronger and more erratic. This is the central finding of an analysis by a team of German researchers that compared more than 30 state-of-the-art climate models from all around the world.

The study predicts more extremely wet years in the future - with potentially grave consequences for more than one billion people's well-being, economy, food systems and agriculture.

We have found robust evidence for an exponential dependence: For every degree Celsius of warming, monsoon rainfalls will likely increase by about 5%. Hereby we were also able to confirm previous studies but find that global warming is increasing monsoon rainfall in India even more than previously thought. It is dominating monsoon dynamics in the 21st century."

Anja Katzenberger, Study Lead Author, Potsdam-Institute for Climate Impact Research (PIK) and Ludwig-Maximilian University in Munich, Germany (LMU)

Too much rainfall can harm plants

More rainfall is not necessarily a good thing for the farming sector in India and its neighboring countries.

As co-author Julia Pongratz from LMU explains: "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-made forcings have begun to overtake slow natural changes occurring over many millennia.

At first, high sun-light blocking aerosol loadings 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.

A threat to the well-being of the Indian subcontinent

"We see more and more that climate change is about unpredictable weather extremes and their serious consequences," comments group leader and co-author Anders Levermann from PIK and Columbia University, New York/USA on the findings of the study published in the journal Earth System Dynamics.

"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."