The Airleaf Journal
Air quality and forest guides Field notes on air, forests and the cities in between
Plain-language, research-backed writing on how to read an AQI number, what is in the air on a bad day, where the world's forests are going, and why city trees matter.
Air quality (AQI) now
- guides
- 16
- topics
- 6
- newest guide
- Oct 30, 2026
India AQI vs US AQI: why CPCB and IQAir differ
The same Mumbai air can read 'moderate' on CPCB and 'unhealthy' on an app. Two scales, two averaging periods, and a crossover most people miss.
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Singapore PSI vs AQI: which haze reading to check
NEA reports a 24-hour PSI and a 1-hour PM2.5 reading; your app shows the US AQI. What each one is for, and how to use them on a hazy day.
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Malaysia's API (IPU) vs AQI: why the numbers differ
Malaysia's Department of Environment reports the API, or IPU; most apps show the US AQI. What each scale means, why they differ, and what to do at each level.
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Wildfire smoke and air quality: why U.S. cities far from any fire get hazardous air
Smoke from a Canadian or Californian wildfire can push New York's or Seattle's AQI into hazardous territory. Here's why it travels so far, and how to stay safe.
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Environmental risks to watch in the U.S. in 2027
No one can predict individual events years out — but the trend lines behind U.S. heat, wildfire, water stress and air quality are already visible today.
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La Niña vs. El Niño: what each one means for U.S. weather
El Niño and La Niña are opposite phases of the same Pacific cycle — and they split the U.S. by region in almost exactly opposite ways.
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What is El Niño, and how does it affect weather across the U.S.?
El Niño reshapes winter weather from Seattle to Florida. Here's what actually causes it, how it splits the U.S. by region, and why no one can control it.
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How satellites track deforestation and urban tree loss
No one is walking every street with a clipboard. Here is how Sentinel-2, Landsat and NDVI actually turn raw satellite pixels into a canopy percentage.
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Best trees to plant in your backyard, by climate
The right tree for a cold, wet garden is the wrong tree for a hot, dry one. A practical starting point for choosing by climate, not by what looked nice at the nursery.
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Carbon offsets vs tree planting: the real difference
Buying an offset and funding a planted, verified tree are not the same transaction. Here is the honest difference, including where offset markets have genuinely struggled.
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Urban heat island effect: why cities run hotter
Concrete, asphalt and glass turn cities into their own weather system. Here is how many degrees hotter that actually means, and why canopy is the cheapest fix.
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How much CO2 does a tree actually absorb per year?
The '48 pounds a year' figure gets quoted everywhere. Here is where it comes from, why it is mostly wrong for any specific tree, and how to think about it honestly.
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How many trees does a city actually need?
The 3-30-300 rule, the 30% canopy target and the simple math Airleaf uses to turn a map circle into a planting number.
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Reading AQI properly: what PM2.5 is really telling you
AQI 150 does not mean 150 of anything. Here is what the index measures, why PM2.5 dominates it, and what to do at each band.
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How to plant a tree that is still alive in five years
Most planting failures happen in the first two summers. Species choice, pit depth, mulch and a watering plan decide the rest.
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Indoor plants and clean air: what actually works
Aloe, snake plant and peace lily are genuinely good houseplants — here is the honest version of what they do for your air.
Read →Reading is step one. Planting is step two.
Check how many trees your own neighborhood has and how clean its air is — then help us plant more with a donation.