NASA, which maintains near-real-time databases of everything from shipping movements to wind patterns, also tracks active large-scale fires around the globe. Their data can be projected onto Google Earth, which I've done here to visualize the remarkable extent of the fires and help show how they've so polluted Singapore from hundreds of miles away.
First, here's the view on Google Earth zoomed in. That little bit encircled in yellow is the entirety of Singapore, population 5.3 million. Above it is the Malaysian peninsula, where 200 schools have been closed due to the air pollution. To the left is the Indonesia island of Sumatra, where the fires are. As you can see, they're quite densely packed. Each of these flames represents a large-scale fire that's occurred just within the past 48 hours:
And here's the view zoomed out. This gives you a sense of how much of Sumatra is burning and why Indonesia – and Singapore – are treating this as such an emergency. Little Singapore is marked by yellow text in the center of the map. Sumatra, to give you a sense of how vast those fires are, is a touch larger than California. But it's much more populous, with over 50 million people. There are also fires visible in Malaysia and the Indonesian island of Borneo.
Finally, I've zoomed out here to show you the fires in relation to all of Southeast Asia. This view is so wide that India, China and the curve of the Earth are all visible. Yet Sumatra is still practically blanketed in flames. Maybe you can understand why Singaporean Prime Minister Lee Hsien Loong says the fires – and the air pollution – could remain for weeks or even months. "It depends on the burning, it depends on the weather, it depends on the wind," he said. "It can easily last for several weeks and quite possibly it could last longer until the dry season ends in Sumatra which may be September or October."
According to a metric called the Pollution Standard Index (PSI), this is the most polluted Singapore's air has been since the measure was first taken. The PSI hit 401 on Friday, way above the 300-point threshold that health officials say is dangerous to public health and even peaking above 400, at which point the air is said to be potentially "life-threatening to ill and elderly persons." Officials have warned Singaporeans to stay indoors.
To give you a sense of why Singaporeans are treating this as so severe, here are two photos from Reuters showing the city skyline after the pollution started and on a normal day:
Indonesia's Minister for People's Welfare accused Singapore of "behaving like a child" for its official and popular outrage over the pollution.