Singapore is starting to look like Beijing or New Delhi. That's because you can't see it through the haze. Smog has disrupted outdoor events, forced schools to close and sent commuters running for their surgical masks.

Singaporeans know why. Every year during the dry season, farmers and plantation companies light fires on the Indonesian islands of Sumatra and Borneo to clear land for farming and the production of paper and palm oil. Wind carries the smoke across the Malacca Strait and the South China Sea.

An especially bad episode in 1997 caused regional outrage and an estimated $9 billion in economic damage. Nearly two decades later, in 2013, air pollution readings in Singapore and Malaysia topped 400 and 700, respectively. (Anything above 301 is considered hazardous.) An El Nino weather pattern this year has raised fears that smoggy skies could persist into 2016.