The screenshots began to circulate on Delhi WhatsApp groups last week, captioned with varying expressions of disbelief. Having checked the air quality index, something of a sadistic morning ritual among residents of India’s capital, most could not believe their eyes. Gone was the familiar menacing red banner, indicating how each intake of breath is really just a toxic blast on the lungs, replaced instead by a healthy, cheerful green. Could it really be that Delhi’s pollution levels now fell into the category of … “good”? “It’s positively alpine!” exclaimed one message.