New PNAS Paper Shows Light Causes Atmospheric Aerosols To Grow – Impact Our Climate

Scientists keep finding major knowledge gaps in their “science-is-settled” field of climatology.

The latest gap is revealed by an experiment by an international team of scientists that shows evidence of a new mechanism where light causes atmospheric aerosols to increase in size.


Aerosol pollution over India and Bangladesh, 2001. (Photo source: NASA)

The results of the research by a team led by Maria Eugenia Monge et al have been published by the PNAS. Title: Alternative pathway for atmospheric particles growth.

“The new and up to now unknown processes may be the reason why the atmospheric chemistry and physics of aerosol concentrations are often underestimated in models. This photo-induced processes first will be characterized experimentally and then introduced to tropospheric models,“ recommends Hartmut Herrmann of the German Leibniz Institute for Tropospheric Research (IfT) in Leipzig, a member of the team.

The paper’s abstract underscores that major gaps exist in the understanding of the physicochemical pathways that lead to aerosol growth in the atmosphere and that these pathways need to be considered by models.

So once again it’s back to the drawing board for our habitually lost climate modellers.

According to a Leibniz Institute for Tropospheric Research press release, light causes the aerosols to grow in size and have an impact on clouds and climate. Photocatalytic reactions can lead to a rapid formation of non-condensing volatile organic compounds (VOCs) on the surface of particles. They found that light can trigger chemical reactions between gaseous bonds and chemicals on the surface of organic particles, which ultimately allows them to increase in size says Dr. Maria-Eugenia Monge of IRCELYON and the University of Lyon.

Experiments showed that the particles under the influence of light can grow about 50 to 65 nanometers, which corresponds to about a doubling of their weight. The intensity of the light was of lesser importance. Already very weak UV radiation is enough to break the chemical bonds of dissolved organic material (DOM) and form free radicals.

The experiments were conducted at the IRCELYON in Lyon under the supervision of Dr. Christian George. Also participating were scientists of the French CNRS research association, the Israeli Weizmann Institute with Prof. Yinon Rudich, and Prof. Hartmut Herrmann of the German Leibniz Institute for Tropospheric Research (IfT) in Leipzig.

The Leibniz press release adds that aerosol particles in the atmosphere influence global climate because they reflect sunlight. They are also a factor in the global water circulation, which effects cloud formation and precipitation. They also impact human health as well. Despite their impacts, the processes that are responsible for the creation and growth of these particles are among the least understood fields of atmospheric science. At the IfT in Leipzig, the development chain of atmospheric particles from fine particulates to the formation of clouds and precipitation in natural areas as well as areas burdened by humans, i.e. large cities, are being researched.

So much for the new study on light and aerosols, which we know have a cooling effect on the planet. But with the last sentence in italics by the IfT, why do I get the feeling they are gearing up (again!) for man-made global cooling? Human activity is throwing up lots of aerosols (industry, agriculture, transportation, etc.) into the atmosphere and so are contributing to blocked sunlight. Time to start curtailing human aerosols!

And one more question: if low intensity light can cause major aerosol growth, wouldn’t it be very plausible that high energy cosmic rays could do the same?


8 responses to “New PNAS Paper Shows Light Causes Atmospheric Aerosols To Grow – Impact Our Climate”

  1. DirkH

    “areas burdened by humans”

    shows their ingrained self-flagellating ideology. Seems to be a constant in academia. What is wrong with these people?

  2. Ric Werme

    Umm, from the post, I have no idea if this has any bearing on the aerosols initiated by cosmic rays. I think the main area of uncertainty in the Svensmark Hypothesis is how to get from the small aerosols initiated by muons (from the particl shower when a cosmic ray hits the upper atmosphere) to a size big enough to be a cloud condensation nucleus. I suspect the authors don’t know either.

    Pierre – I get the sense that the higher and steady photon flux is needed for aerosol growth. Muons act on molecule sized object to give them a charge and get things started, it seems the light makes VOCs be non-volatile, by chemical reaction. It’s certainly something the folks at CERN should notice and explore in their CLOUD experiment if appropriate.

    1. Bernd Felsche


      As I (mis)understand it, a “particle’s” energy has to provide enough energy to facilitate bonding (by ionization). If there isn’t enough in one “event”, then the energy is lost and doesn’t contribute to the next event.

      A greater flux of such sufficiently-energetic particles increases the probability of collision, ionization and bonding. That seems to work at all molecular scales.

  3. DirkH

    Thousands of muons pass through us every minute!

    1. Bernd Felsche

      Deja muon 😉

  4. Pierre Gosselin: New PNAS Paper Shows Light Causes Atmospheric Aerosols To Grow – Impact Our Climate |

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  5. Snorbert Zangox

    I think that they are talking about the same photochemistry that we have been studying since the late 1950s, wherein photons of light initiate reactions that cause formation of free radicals, organic compounds and organic and inorganic solids. Smog reaction studies began in the Los Angeles area 50 years ago. None of this is new.

    1. DirkH

      The abstract says “The current study presents experimental evidence of an unaccounted-for new photoinduced pathway for particle growth.” – meaning the particular pathway they describe has not been described before.