Simulations reported in a Nature Communications preprint find abrupt aerosol increases can warm the atmosphere for about 48 hours before their reflective cooling dominates. Models led by Prof. Guy Dagan show peak short-term heating near 20 W/m² on day one, driven by cloud changes that lift moisture and form high ice clouds. The lagged response means timing of observations matters for satellites and climate models.
Atmosphere 'Remembers' Pollution: Aerosol Spikes Can Heat The Sky For ~48 Hours Before Cooling
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New research indicates that sudden increases in aerosol particles from human emissions or wildfire smoke can briefly warm the atmosphere for roughly two days before the particles’ familiar cooling effect takes over. The study, posted as a preprint in Nature Communications, challenges the assumption that aerosols immediately lower surface temperatures after an injection event.
What the study found
Simulations led by Prof. Guy Dagan (Hebrew University of Jerusalem) tracked atmospheric responses in the days after abrupt rises in aerosol concentrations. The models show that heat can remain trapped for about 48 hours, with the strongest short-term warming — near 20 watts per square meter — occurring during the first day.
Why this happens
The brief warming appears tied to rapid cloud adjustments. Higher particle counts can suppress light precipitation, lift more water vapor into higher layers of the atmosphere, and promote the formation of elevated ice clouds. Those upper-level clouds trap outgoing longwave radiation that would otherwise escape to space, producing a temporary warming signal. As the cloud response fades, the aerosols’ reflective (sunlight-scattering) effect becomes dominant and the net impact shifts back toward cooling.
Implications
Aerosols remain one of the largest uncertainties in climate projections because of their complex interactions with clouds. The study suggests that measurements taken at a single moment may miss this lagged response: whether a pollution pulse warms or cools can depend on when it is observed as well as how much material is present. If aerosol concentrations fluctuate on multi-day timescales, the atmosphere might rarely reach the later cooling phase, which could affect how researchers estimate the short-term climate impact of pollution and wildfire events.
Context and caveats
The work appears as a preprint and is based on model simulations; observational confirmation and further study will be needed to quantify how common and large this effect is in the real world. Reporting on the preprint was covered by outlets including Earth.com and Phys.org. As Dagan summarized:
"Our results show that the atmosphere has a memory."
Note: This article summarizes a preprint study and related reporting; readers should watch for peer-reviewed publication and follow-up observational research.
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