Explainers

Explainers · 18 OctWhat is ISPU? Indonesia's air quality index, and how it compares with the US AQIWhat is ISPU? Indonesia's official air quality index runs from Baik to Berbahaya. The five levels, what each means, and why it reads lower than the US AQI.

• ExplainersFirst freeze of the season: what a freeze warning, freeze watch and frost advisory mean this weekendFreeze warning vs frost advisory: what each NWS alert means, where the first freeze hits the Plains and Midwest on 16 and 17 October, and how to protect plants.16 Oct · 5 min read
• ExplainersEl Niño 2026 could be the strongest on record: what it means for this winter's weatherEl Nino is heading for a strong to very strong peak this winter 2026-27, possibly the strongest since 1950. What it means for rain, heat and haze worldwide.15 Oct · 5 min read
• ExplainersPM2.5 vs PM10: what's the difference, and which one should you worry about?PM10 is coarse dust up to 10 micrometres; PM2.5 is fine smoke and soot up to 2.5. PM2.5 vs PM10 explained, with safe levels and today's examples.15 Oct · 5 min read
• ExplainersGRAP explained: what each stage means for Delhi NCR in winter 2026What Delhi NCR's Graded Response Action Plan does at each stage, from dust control at Stage 1 to truck bans at Stage 4, and what changed in 2026.14 Oct · 4 min read
• ExplainersStubble burning explained: why farmers burn paddy straw and how it reaches DelhiWhy farmers in Punjab and Haryana burn paddy straw each autumn, how much it adds to Delhi's smog, the alternatives, and 2026 farm fire data.14 Oct · 4 min read
• ExplainersUS AQI vs India's AQI: why the same air gets two different numbersThe US AQI is stricter in cleaner air; India's NAQI climbs faster in heavy smog. Why the same air gets two numbers, with a conversion table.14 Oct · 3 min read