In a small laboratory on the outskirts of the Indian city of Hyderabad, professor Kirti Sahu is studying raindrops.

Using a machine that simulates the conditions of clouds, he is among a number of scientists aiming to understand how climate change and pollution are changing the monsoon rains that underpin the country's agrarian economy.

"The Indian monsoon is full of mystery. If we can predict rainfall, it will be huge for us," said Sahu, a researcher in the department of chemical engineering at the Indian Institute of Technology Hyderabad.