Just as we hit Karnal, 130 km north of New Delhi, in Haryana on National Highway 1, a noxious odour and a mild haze are all but obvious. As we turn left off the highway, their source comes into view: large stretches of agricultural fields coated in various shades of black, with the embers still fresh on some. Burning the residues of the rice crop after harvest in winter, and of wheat …