The South Asian monsoon was not always something to be dreaded. At one time, it was welcomed by farmers and other citizens alike. But this year, floods in Pakistan have killed more than 1,000 people after a record unbroken cycle of monsoon rains with “8 weeks of non-stop torrents”.

What is a monsoon, why it is so important and yet so dangerous, and how are climate change and other man-made effects altering the vast life-giving but destructive annual weather system — this article tries to answer some basic questions.

The Southwest or the Asian Summer Monsoon is essentially a colossal sea breeze that brings South Asia 70-80 percent of its annual rainfall between June and September every year.

It occurs when summer heat warms the landmass of the subcontinent, causing the air to rise and sucking in cooler Indian Ocean winds which then produce enormous volumes of rain.

It 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 also 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.

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.

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 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.India’s 2021 monsoon was a case in point: June rain was above normal, in July it fell, August was nearly a drought and in September precipitation returned with a vengeance.

Several hundred died in floods in Maharashtra in July and in Gujarat in Sep­tember. The same month a cloudburst turned the streets of Hyderabad into raging rivers in just two hours.

Published in Dawn, August 30th, 2022