NEW DELHI:
More than 1,000 people have died in floods in Pakistan as a result of what the country’s climate change minister described as a “8-week stretch of non-stop torrents” during the monsoon season.
The massive, life-giving yet devastating annual weather system, the monsoon, is described by AFP along with why it is so vital and yet so hazardous, and how climate change and other man-made factors may be affecting it.
What is the South Asian monsoon?
South Asia receives 70–80 percent of its yearly rainfall between June and September thanks to the Southwest Monsoon, also known as the Asian Summer Monsoon.
It happens as the subcontinent’s landmass warms in the summer, forcing the air to rise and draw in cooler breezes from the Indian Ocean, which subsequently generate a huge amount of rain.
Why it is important?
The monsoon is vital for agriculture and therefore for the livelihoods of millions of farmers and for food security in the poor region of around two billion people.
But it brings destruction every year in landslides and floods. Melting glaciers add to the volume of water while unregulated construction in flood-prone areas exacerbates the damage.
Is it the same every year?
Despite being heavily studied, the monsoon is relatively poorly understood. Exactly where and when the rain will fall is hard to forecast and varies considerably.
This year, for example, while Pakistan has seen a deluge, eastern and northeastern India reportedly had the lowest amounts of July rainfall in 122 years.
What explains the variability?
Fluctuations are caused by changes in global atmospheric and oceanic conditions, such as the El Nino effect in the Pacific and a phenomenon called the Equatorial Indian Ocean Oscillation (EQUINOO) only discovered in 2002.
Other factors are thought to include local effects such as aerosols, clouds of dust blowing in from the Sahara desert, air pollution and even irrigation by farmers.
What about climate change?
India is getting hotter and in recent years has seen more cyclones but scientists are unclear on how exactly a warming planet is affecting the highly complex monsoon.
A study last year by the Potsdam Institute for Climate Impact Research (PIK) tracking monsoon shifts from the mid-20th century suggested that it was becoming stronger and more erratic.
Initially, aerosol pollution reflecting sunlight subdued rainfall, but from the 1980s the warming effects of greenhouse gases began to drive stronger and more volatile rainy seasons, the study said.
Do other studies bear this out?
Broadly yes. The Indian government’s first ever climate change assessment, released in 2020, said that overall monsoon precipitation fell around six percent from 1951 to 2015.
It said that there was an “emerging consensus” that this was down to aerosol pollution considerably offsetting the expected rise in rainfall from global warming.
With continued warming and lower aerosol emissions, it projected more rain and greater variability by the end of this century, together with “substantial increases” in daily precipitation extremes.
What will this mean for people?
One such example was the Indian monsoon of 2021: June rains were above average, it rained in July, August was almost a drought, and in September precipitation came back with a fury.
In Gujarat in September and Maharashtra in July, many hundred people perished in floods. In the same month, a cloudburst transformed Hyderabad’s streets in under two hours into raging floods.
However, by October, farmers in some areas of northern and north-eastern India were suffering from drought, while in other areas the monsoon’s withdrawal took longer than usual.
Anders Levermann from PIK and Columbia University told AFP last year that “more instability in the Indian monsoon rainfall will make it tougher to adapt.”
