“We know how to cook without smoke,” said Veerabhadran Ramanathan, a University of California, San Diego climatographer. “A clean stove costs $30 (£18). Multiply that by 500 million households, and it’s only $15 billion. This is a solvable problem.”

Clean stoves use the same fuel, but burn it more efficiently, reducing fuel consumption and the amount of smoke produced. After floating to the atmosphere, black carbon from smoke mixes with dust to form a solar heat-absorbing particulate layer. Raindrops form around the particles, trapping even more heat. Soot deposited by the rain heats up, too.

The climate dynamics of the black carbon process have been fully described only in the last decade, but scientists now say their short-term impact sometimes rivals that of carbon dioxide. As much as one-half of the 3.4 degree Fahrenheit rise in Arctic temperatures since 1890 is attributed to black carbon. By disrupting weather patterns, it may be responsible for weakening seasonal rains in South Asia and West Africa. And black carbon is also a major reason why Himalayan glaciers, which provide water to hundreds of millions of people, are vanishing.

Unlike carbon dioxide, however, which can hang in the atmosphere for centuries, black carbon returns to Earth in less than a month. And that makes it a ripe target for immediate action. Though Ramanathan is quick to warn that eliminating black carbon is no substitute for controlling carbon dioxide emissions, which in coming centuries could have a far greater effect, he estimates that a 50% reduction in black carbon could delay the onset of severe global warming by one to two decades.