The study combined nearly two decades of satellite observations with modern atmospheric reanalysis to examine aerosols—tiny airborne particles from pollution, wildfires and volcanoes—and their effect on clouds and reflected sunlight. The researchers report opposing aerosol trends between the hemispheres.
In the Northern Hemisphere, cleaner air over industrial regions reduced particles that help clouds reflect sunlight, allowing more solar energy to reach the surface. In the Southern Hemisphere, large increases in natural aerosols after major wildfires and a volcanic eruption made clouds brighter and increased reflection to space.
Because the two effects largely cancel, the team concludes aerosols had little net global effect on the recent rise in Earth’s heat imbalance. From 2003 to 2023, Earth gained heat at a faster rate, driven mainly by changes in reflected sunlight rather than changes in heat escaping to space.
Difficult words
- aerosol — tiny particles in the air from many sourcesaerosols
- reanalysis — processed historical weather and atmospheric data for study
- hemisphere — one half of the Earth, north or southhemispheres
- reflect — send back light or energy from a surfacereflected
- wildfire — a large, uncontrolled fire in natural areaswildfires
- heat imbalance — difference between incoming and outgoing Earth energy
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Discussion questions
- Why might cleaner air in industrial regions allow more solar energy to reach the surface? Explain in two sentences.
- How could brighter clouds after wildfires or a volcanic eruption affect local weather or temperature? Give one possible effect.
- The study says the two hemispheric effects largely cancel. What other factors should scientists study to understand the rise in Earth's heat? Give one or two ideas.
