People from Beijing to Delhi to Los Angeles have noticed bluer skies and less haze as lockdowns were imposed for the pandemic. But this year is still in track to be the hottest year on record. Why is the air getting cleaner yet warmer? Salad observations of nitrogen dioxide, a byproduct of burning fossil fuels, show that levels of that air pollutant are going down. Clear skies also tell us that there's less particulate matter in the air. Particles are tiny bits of soot and other substances floating in the air. Particles reflect the way sunlight, so paradoxically fewer particles might mean more warming. But while those pollutants stay in the air for days, the heat-trapping gas carbon dioxide remains in the atmosphere for centuries. Carbon dioxide levels will only stabilize when emissions fall into a net zero bounce with sinks of the gas, like vegetation and oceans. Even with declines in CO2 this year, the earth is nowhere near achieving that balance.