Despite the varying contexts, a climate change connection is evident in recent floods across China and India, as well as in Germany, Belgium and the Netherlands, says Sanjay Srivastava, Chief, Disaster Reduction, UN-ESCAP. Extreme flood events have recently hit several parts of Asia and Europe, too.

Floods in the Asia-Pacific region have been frequent and devastating both in terms of fatalities and economic losses. Globally, 10 out of the top 15 countries with the most people exposed to annual river floods are in the Asia-Pacific region. In order of population exposed to flood risk, they include India, Bangladesh, China, Vietnam, Pakistan, Indonesia, Myanmar, Afghanistan, Thailand and Cambodia.

Combination of factors

Floods are the result of a combination of two factors: first, heavier-than-normal rainfall and second, limited capacity of rivers, drainage and water harvesting structures to withstand and discharge the excess rainwater, especially in a short time span, Srivastava wrote in an Email to BusinessLine.

In all these recent events, the floods followed a period of unusually heavy rain, equivalent to almost a year’s rainfall being dumped in just a couple of days in some cases, overwhelming flood defenses.

Extreme event studies provide mounting evidence that climate change raises the risk of extreme weather events like heat waves, heavy rain and flooding, drought, cold/snow, storms, oceans and wildfires. Intense rainstorms are expected to be more frequent due to global warming as warmer air holds more moisture.

More intense storms

Research also shows that climate change might make the storms producing intense rain across Europe move slower, increasing the duration of local exposure. It thus increases the number of large, slow-moving storms that can linger for long in one area and deliver deluges as seen in Germany and Belgium.

While China experiences severe flooding every year causing loss of life and property, this year’s intensity was unprecedented as the central Henan province witnessed its heaviest rainfall in 1,000 years. Initial observations suggest that the typhoon In-Fa may have been responsible for the heavy rainfall.

The typhoon and the air currents carried atmospheric water, concentrating at Zhengzhou city, which is surrounded by mountains, creating a basin effect, Srivastava. Likewise in Maharashtra in India, the recent floods were a consequence of 600-900 per cent excess rain in many severely affected districts.

Potent offshore trough

As the South-West monsoon turned extremely active over India after a long break that ended on July 13, 2021, the rainfall was caused by an offshore region of extended lower pressure known as a ‘trough’ that runs from India’s long West Coast (from South Gujarat to Kerala) straddling the Arabian Sea.

Climate change is making the Indian monsoon seasons more chaotic with substantial disruptions in weather patterns and for every degree Celsius of warming, Srivastava pointed out.