A study from the Hebrew University of Jerusalem shows that aerosols can affect the climate differently over different timescales. The researchers emphasize that this is not a solution to the climate crisis, but a way to improve climate models.
Tiny particles in the atmosphere, called aerosols, are one of the most complex components of the climate system. They are created by air pollution, fires, dust, sea spray, and other natural and human sources. They affect clouds, the radiation that is reflected back into space, and the heat that remains in the atmosphere. New research from the Hebrew University of Jerusalem shows that their impact is not constant: it also depends on the amount of time that has passed since the concentration of the particles in the air changed.
It is important to emphasize at the outset: The study does not suggest that air pollution is a solution to the climate crisis, nor does it challenge the fact that greenhouse gases cause global warming. Aerosols are also air pollutants that harm human health and ecosystems. The goal of the study is to better understand how clouds and the atmosphere respond to rapid or slow changes in particle concentrations, in order to improve climate predictions.
The study, published inNature Communications., led by Prof. Guy Dagan from the Freddie and Nadine Herman Institute for Earth Sciences at the Hebrew University. According to the researchers, aerosols are one of the largest sources of uncertainty in climate models, in part because they affect clouds in different and time-dependent ways.
Not just how many particles – but also when
Aerosols can act as nuclei around which cloud droplets form. In doing so, they influence the structure of clouds, their height, their lifespan, and the way they reflect radiation or trap heat. It has been known for years that such particles have a significant impact on climate, but it has been very difficult to quantify.
The new study examined what happens after a sudden change in aerosol concentration. According to the simulations, in the first two days after an increase in particle concentration, a local or regional warming effect may occur, in part due to changes in high clouds that trap heat that could otherwise be emitted into space. But then the atmosphere responds: upper layers warm, cloud patterns change, and the system can switch to a different response, which in some cases leads to a cooling effect.
The key point is not that aerosols “cool the Earth” in a simple or desirable way, but that their effect depends on a dynamic process. The same amount of particles can have a different effect if measured immediately after a sharp change, or after the atmosphere has had time to respond.
Atmospheric “memory”
One of the important concepts in the research is “atmospheric memory.” This means that the atmosphere responds not only to its current state, but also to its recent history: whether the concentration of aerosols has increased or decreased, at what rate, and how much time has passed since the change.
Therefore, spot measurements of clouds and particles may give a partial picture. If the atmosphere is measured at only one moment, it is possible to misjudge the overall impact of aerosols. The researchers suggest taking into account the development of the process over days, and not just the momentary situation.
According to Prof. Dagan, “Our results show that the atmosphere has a memory. The climate impact of aerosols depends not only on the number of particles in the air, but also on the rate at which conditions change and the time the atmosphere has had to respond.”
Not a climate solution, but an improvement in understanding
The study is important because climate models need to account not only for the impact of greenhouse gases, but also for the response of clouds, particles and radiation. Some aerosols can reflect radiation and contribute to local cooling, while others affect clouds in complex ways, and the impact varies with altitude, region, season and weather conditions.
But this complexity does not make aerosols a desirable policy tool. Reducing air pollution is essential for public health, and reducing greenhouse gas emissions remains the key tool for dealing with the climate crisis. The new study addresses a different scientific question: how to better represent the response of clouds and the atmosphere to changes in particles, to reduce uncertainty in predictions.
If the mechanisms described in the study are incorporated into future models, they could help scientists better assess the impact of aerosols on climate. In doing so, they could contribute to more accurate predictions – not to justify continued emissions, but to better understand the complex system in which we are already interfering.
for the scientific article In Nature Communications.
Short FAQ:
What are aerosols? Tiny particles floating in the atmosphere and originating from dust, fires, sea spray, air pollution, and other sources.
Does the study claim that air pollution solves the climate crisis? No. The study is about understanding the impact of aerosols on clouds and climate, and does not suggest using air pollution as a solution.
Why is the research important? Because aerosols are a major source of uncertainty in climate models, understanding their impact over time can improve climate predictions.
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