South Asia monsoon: climate change's dangerous impact on lifeline rains

South Asia's annual monsoon rains sustain more than a billion people, but climate change is making them increasingly erratic and deadly, with poor infrastructure only exacerbating the impact.

Farming, water supplies and hydropower across much of South Asia rely on the seasonal rains, but research shows climate change is causing longer dry spells punctuated by bursts of extreme rain.

- What is the monsoon? -

Derived from the Arabic "mausim", or season, the monsoon is a reversal of winds driven by differences in land and sea heating. These patterns are observed in several places on Earth.

In South Asia, the Southwest Monsoon brings rains that start in southern India in late May and sweep north until September.

By October, the Northeast Monsoon begins. As the land cools, winds blow seawa