2023-09-16 15:21:27
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[EN VIDÉO] The fascinating world of clouds Watch the clouds go by: they come in all shapes. We…
To limit global warmingglobal warming, we must, among other things, plant treestrees. And leave it to them to capture the CO2 that we will continue to emit into our atmosphere. It has become the gimmick of a number of political figures. Science teaches us that, as is often the case, things are a little more complex. And researchers are even interested in a completely different impact that trees might have on our climateclimate. An international collaboration of the European Organization for Nuclear Research (CernCern, Switzerland) called Cloud – for Cosmics Leaving Outdoor Droplets – has just made an important discovery published in the revue Science Advances.
The researchers thus identified a class of moleculesmolecules from the terpenesterpene family, sesquiterpenes (C15H24), as a major factor in the formation of clouds. However, these sesquiterpenes are released by trees and plants.
A link between trees and clouds
To understand, let us recall that, to form clouds, water vapor droplets need some sort of support on which to condense. Aerosolsaerosols, solidsolids or liquidliquids, of not more than 10 micrometersmicrometers in diameter. Desert sand or sea salt, for example. But half of the condensationcondensation supports are built from tiny molecules of gasgas which combine. Sulfur dioxide molecules resulting from the combustioncombustion of coalcoal and petroleumoil, in particular. Again, sesquiterpenes emitted by trees.
Environmental legislation has reduced sulfur dioxide concentrations. And this will continue. Sesquiterpene emissions, on the other hand, are increasing. Because a stressed tree — by rising temperatures or drought — emits more than a tree growing in good conditions. So to provide accurate climate forecasts, researchers needed to know which of these phenomena should dominate in the future. Leading to the formation of fewer or more clouds. Knowing that when cloud cover increases, more solar radiation is reflected back into space. Which has the gift of refreshing the EarthEarth.
A discovery regarding trees that should improve climate models
Until now, sesquiterpenes were little studied, because they were less abundant than other substances — also emitted naturally by plants. Each year, around 495 million tonnes of isopreneisoprene are released into the atmosphere compared to only 24 million tonnes of sesquiterpenes. But the Cloud collaboration researchers have just discovered that at the same concentration, the latter would form ten times more particles involved in the formation of clouds. A discovery made thanks to a unique 30 cubic meter climatic chamber in which they were able to simulate different atmospheric conditions.
The researchers believe that the effectiveness of sesquiterpenes in forming particles that can become condensation media for clouds may be due to the number of carboncarbon atoms the molecule contains. Where a terpene contains only five carbon atoms, a sesquiterpene contains fifteen!
The latest climate models are more uncertain and it’s the clouds’ fault
With these new data in hand, climatologists should be able to refine their models. And thus offer more precise forecasts of what awaits us.
Climate: according to CERN, trees influence cloud formation
As the results of the Cloud experiment at Cern showed in 2016, trees would be much better than we thought at making clouds and cooling the climate. Their action occurs through aerosols.
Article of Laurent SaccoLaurent Sacco published on 16/102016
Since 2009, the experience Cloud, installed at CERN in Geneva, simulates different pressure pressure and temperature conditions to study mechanisms at work in the Earth’s atmosphere, and in particular the effect of aerosols on the climate. These small particles act like “cloud seeds”, promoting the condensation of water vapor into droplets and therefore the formation of cloudiness. Overall, the effect on the climate is cooling because part of the sunlight is then reflected upwards.
Half of these aerosols are dust from land and sea salts emitted by the ocean and, for the other half, gas molecules which aggregate into particles of 50 to 100 nanometers. This is the case for sulfuric acidsulfuric acid, derived from sulfur dioxide (SO2). Today, this gas is produced with great generosity by industrial activities. These human-made aerosols, by creating more clouds, have a cooling effect, which reduces the warming effect of carbon dioxidecarbon dioxide (CO2). This is radiative forcing. Trees are also players in this machinery, with molecules, such as pinene, released into the air and also play the role of condensation nuclei.
Current amounts of sulfur dioxide emissions make it difficult to study the pre-industrial atmosphere, which was different. This is what a Cloud team did, which used the results of this experiment to build a simulation of the pre-industrial atmosphere. Their conclusions, published in the Pnas (and discussed in an article by The conversation), specify previous studies, presented in our previous article, below.
According to these results (still uncertain, specify the authors), the quantities of aerosols present in the earth’s atmosphere before 1750 have until now been underestimated, because the aerosols emitted by trees are much more effective than we thought to make clouds. As a result, the cooling effect of industrial aerosols would be lower than expected, by around 27%.
The authors also deduce that limiting aerosol emissions from human activities might reduce their cooling action. But this decline might be offset by the action of trees, which are just waiting to regain the importance they had in the pre-industrial era. In short, forests are capable of helping us limit global warming…
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Initial article published on 05/30/2014 at 10:29
The Earth is a dynamic system with complex couplings and feedback loops between atmosphere, hydrospherehydrosphere, biospherebiosphere and even the interior of the globe. Members of the Cloud experiment at Cern have just illustrated this once more by showing that the formation of clouds can be linked to vapor emissions from trees. The planet’s climate is therefore influenced by its forest cover.
At Cern, we don’t just study exotic nuclei and the Higgs boson or even hunt for dark matter particlesdark matter with the experiment Osqar (Optical Search of QEDQED vacuum magnetic birefringence, AxionAxion and photonphoton Regeneration). Researchers are also trying to better understand the physics of cloud formation with the Cloud experiment (Cosmics Leaving Outdoor Droplets). This fog chamber (coupled with a reaction chamber), powered by the Proton Proton Synchrotron (PS) at Cern, is used to study a possible link between cosmic raysgalactic cosmic rays and the formation of clouds. The temperature and pressure conditions of any location in the atmosphere on Earth can be recreated and it is also possible to modulate the intensity of the particle beams reproducing the effect of cosmic rays on the nucleationnucleation of droplets. ‘water.
This instrument thus makes it possible to study in particular the formation of aerosols which can serve as condensation nuclei and therefore their influence on the formation of clouds. As the latter modify radiative transfers in the atmosphere, this type of experiment can shed light on poorly understood phenomena playing a more or less important role in the evolution of our planet’s climate.
Sulfuric acid and alpha-pinene: a recipe for clouds
Recently the members of the Cloud collaboration published in Science an article concerning the impact of certain aerosols emitted by forest trees on cloud formation. According to Cloud spokesperson Jasper Kirkby, “This is a very important result, as it identifies a key ingredient responsible for the formation of new aerosol particles throughout much of the atmosphere. However, aerosols, with their influence on clouds, have been recognized by the IPCC as the greatest source of uncertainty in current climate models..
Members of Cloud, which includes atmospheric physicists, SunSun physicists, as well as cosmic ray and particle physicists from 18 institutes in 9 countries, discovered that biogenic vapors emitted by trees can combine, at the end of oxidation reactions in the atmosphere, with the sulfuric acid it contains.
Resulting from this combination, atmospheric particles appear whose formation rate increases sharply under the action of galactic cosmic rays but only when the concentrations of sulfuric acid and oxidized biogenic vapors are relatively low. These particles in turn promote the nucleation of water drops and therefore the formation of clouds. The inclusion of this mechanism in a global model of photochemical aerosol formation seems to make it possible to reproduce observed seasonal variations. The concentration of aerosols would thus increase, the authors explain, in response to the overall increase in biological emissions from forests during the northern summer.
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