Pollution Particles Warm the Atmosphere for 48 Hours Before They Cool It

Particles from wildfires, industrial exhaust and sea spray have been tagged for decades as the climate's reluctant air conditioners. A new study from Hebrew University of Jerusalem says the first chapter of that story runs backward.

These particles, which atmospheric scientists call aerosols, are not the spray-can propellants that damaged the ozone layer in the 1980s. They are the microscopic bits of soot, dust and salt suspended in the lower atmosphere, and their effect on climate has always been hard to pin down. Now it is more complicated still.

Prof. Guy Dagan ran high-resolution simulations tracking what happens right after particle concentrations jump. The first two days looked wrong. The particles triggered more high-altitude cloud formation, and those clouds trap heat. The warming peaked at about 20 watts per square meter on day one. After that, the atmosphere settled into the cooling pattern the models had assumed all along.

The problem was the sequence. These particles are already among the largest sources of uncertainty in climate projections. The study, published in Nature Communications, adds a layer: the effect changes direction depending on when you look. The immediate response and the settled response run in opposite directions.

Climate models captured the right long-term answer. They were built on it. What they were missing was everything that happens first.

The atmosphere has been running a 48-hour heater before switching to air conditioning every time pollution spikes. Scientists just got a better look at the thermostat.

Read the full story at Phys.org, June 8, 2026

Hot Take: The thermostat was right. The sequence was not. Those are different problems, and only one of them was in the climate models.