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Since the rise of industrialization more and more greenhouse gases are being emitted into the atmosphere and as a result the earth’s climate is warming. It is known that part of the temperature rise is balanced by aerosol particles in the atmosphere – partly also emitted by human activity. The extent of that balancing however is unknown. As BJORN B. STEVENS explains in this video, the researchers used a new approach to estimate how strong this effect actually is: they used a top down perspective and asked if the assumptions made in earlier studies are consistent with current observations. Their findings show that the cooling effect of aerosol particles is not as large as previously calculated. Most significantly, this means that we do not have to fear an increase of global warming due to cleaner air.


Bjorn B. Stevens is Director of the Department for the Atmosphere in the Earth System, at Max Planck Institute for Meteorology and teaches at the University of Hamburg. Previously, Stevens was a Professor of Dynamic Meteorology at the University of California, Los Angeles (USA).

Stevens has made major contributions to the research on atmospheric convection in the climate system. He was awarded the Clarence Leroy Meisinger Award of the American Meteorological Society, and is an associate fellow at various institutions, including the Alexander von Humboldt Society.


Max Planck Institute for Meteorology

The Max Planck Institute for Meteorology (MPI-M) is an internationally renowned institute for climate research in Hamburg, Germany.

Our scientists develop advanced models of the Earth system, perform targeted observations, and advance theoretical concepts to support the institute´s chosen mission: 'To understand Earth's changing climate'. The MPI-M comprises two departments: The Atmosphere in the Earth System and The Ocean in the Earth System. We run an international PhD program together with the University of Hamburg and host independent research groups. The institute was founded in 1975 and is part of the Max Planck Society.

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Original publication

Rethinking the Lower Bound on Aerosol Radiative Forcing

Stevens Bjorn
Journal of Climate
Published in 2015