October 1st, 2018 : Researchers Study The Atmosphere Of Jupiter And The Atmosphere Of Titan In Order To Better Evaluate The Impact Of Methane On Global Warming

A new study entitled  Large regional shortwave forcing by anthropogenic methane informed by Jovian observations , published in the journal Science Advances on September 26, 2018 and proposed by a team involving Daniel R. Feldman reveals that the study of Jupiter's atmosphere and of Titan's atmosphere allows us to better evaluate the impact of methane on our climate and the influence of methane on global warming on Earth. The atmosphere of Jupiter is dominated by hydrogen and helium but it also contains a relatively significant fraction of methane. The atmosphere of Saturn's largest moon Titan is dominated by nitrogen and the second most abundant gas in that gas blanket is methane. Therefore, researchers are in a position to study the potential influence of methane on environmental temperatures on Titan's surface or in the upper atmosphere of Jupiter. They can evaluate in a more precise way the influence of the increase in the level of methane in our atmosphere on the well-known phenomenon of global warming here on Earth.

The phenomenon of global warming appears to be closely related to greenhouse gases such as carbon dioxide or methane. Several types of gas can produce global warming or can increase the environmental temperature. Carbon dioxide, methane and water in the form of gas can trap the heat or the radiations from the Sun and engender a rise in the environmental temperature at sea level. Industrial or developed countries like China, France, Great Britain or Germany engender a lot of carbon dioxide via the burning of fossil fuels. And the level of carbon dioxide released into the atmosphere or into our environment tends to increase over time. The global economy is inexorably growing implying significant increases in the release of greenhouse gases such as carbon dioxide and methane. We often focus our attention on the role of carbon dioxide or CO2 regarding the impact of greenhouse gases on global warming but we tend to forget that methane or CH4 is a much more potent greenhouse gas than carbon dioxide. According to the Intergovernmental Panel on Climate Change (IPCC), the molecule of methane is more than 25 times more powerful than carbon dioxide in terms of warming effects in our environment and on our planet over the span of a century.

The study of Daniel R. Feldman and his group unveils the potential extent of the impact of short-wavelength solar radiation on the properties of methane in terms of warming effects in our Terrestrial environment. The planetologists wanted to know how much shortwave light was absorbed by the methane present in the atmosphere because the influence of that type of solar radiation on the level of warming effect of methane had probably been underestimated. In fact, previous estimates performed by the Intergovernmental Panel on Climate Change or IPCC regarding the relationship between the rise in the level of methane released and the evolution of global climate or the phenomenon of global warming hadn't taken into account the influence of shortwave absorption by methane molecules. Recent climate models incorporate the parameter of the way methane molecules absorb shortwave radiations. Researchers want to know the exact absorption level of shortwave radiations by methane but recent climate models are not particularly accurate regarding the influence of shortwave light on global warming because there are uncertainties regarding the level of shortwave light absorption by methane molecules.

The study of the interaction between shortwave light and methane appears particularly complex due to the relatively complex geometry of the methane molecule which has a tetrahedral shape whereas the carbon dioxide molecule unveils a relatively simple linear shape. As a result, the analysis of the interactions between shortwave radiations and methane which is composed of one carbon atom and four hydrogen atoms is far from being obvious. What is the fraction of shortwave light that is reflected by methane molecules ? What is the fraction of shortwave light that is absorbed by methane molecules ? The simulations in the laboratory don't engender the perfect result. That's why planetologists or climate specialists try to collect clues or key information regarding the chemistry and the dynamics of the atmosphere of the Gas Giant Jupiter and of the giant moon Titan. Daniel R. Feldman who is a co-author of the research work and who is a climate scientist at Lawrence Berkeley National Laboratory in Berkeley, California pointed out that the atmosphere of Jupiter and the atmosphere of Titan, two worlds of the Outer Solar System, have  at least a thousand times greater concentration of methane than Earth's atmosphere .

Jupiter appears to be a world of gas largely dominated by hydrogen and helium but it also contains relatively significant concentrations of ammonia, methane or water. The concentration of methane in the atmosphere of Titan that is dominated by molecular nitrogen like the atmosphere of our planet is relatively high, representing more than 1% of the overall composition. Methane can reach around 5% of the atmospheric composition close to the soil of Saturn's largest moon. Therefore, Daniel R. Feldman advanced that those worlds can represent  natural laboratories  to study the effects of solar radiations on methane. Under the action of ultraviolet light from our star, methane molecules are supposed to disappear over time in the Titanian atmosphere. However, the complex haze of Titan that is rich in organics and hydrocarbons can engender new molecules from simple hydrocarbons to complex organics under the action of UV light from the Sun. Furthermore, there may be internal sources of methane beneath the crust of that intriguing moon.

The complex atmosphere of the Opaque Moon produces greenhouse effects and anti-greenhouse effects. The dynamics, the climate and the meteorology of Titan appear clearly complex because we don't have all the elements of the puzzle in particular. We have to take into account seasonal factors, orbital factors as well as characteristics of Titan's soil. The researchers studied data of the Orange Moon obtained from the Huygens probe during its atmospheric plunge and its touchdown on Saturn's largest moon on January 14, 2005. They also analyzed data of the Gas Giant Jupiter acquired from the Hubble Space Telescope of NASA. The amount of data collected and analyzed by the planetologists allowed them to determine the way methane molecules absorb the different short wavelengths of solar radiation. They could incorporate the data into climate models of the Blue Planet for a more accurate outcome. The distribution of methane in our atmosphere is far from being uniform like in the atmosphere of Titan making the analysis on the thermal impact of methane particularly difficult.

The team of Daniel R. Feldman determined that the effects of methane on climate change or global warming are apparently not uniform on our planet and that they depend on the location or the area. Daniel R. Feldman argued that the absorption of solar radiations with a short wavelength is 10 times stronger over regions such as the Sahara desert and the Arabian Peninsula than elsewhere on our planet for instance because deserts close to the equator unveil bright, exposed surfaces that reflect solar radiations upward. Furthermore, the absorption of shortwave radiations by methane can be multiplied by three with the presence of clouds. Those effects have been identified in the west of southern Africa and the Americas as well as with the systems of clouds in the Intertropical Convergence Zone close to the equator. Daniel R. Feldman advanced :  We can really nail down the methane greenhouse effect on Earth based on observations of Jupiter and Titan.  The discoveries of the planetologists are in line with previous climate models regarding the effects of the increase in released methane on the evolution of our climate and the phenomenon of global warming.

The group of researchers advanced that the new study could allow us to improve the climate-change mitigation strategies thanks to a better evaluation of the risks that the different areas of the world face today. Planetology allows us to study the effects of greenhouse gases such as methane, carbon dioxide or water on the level of heat or on the environmental temperature. For instance, the study of Venus and its atmosphere has allowed us to discover the surprising greenhouse effects generated by carbon dioxide and clouds of sulfuric acid. We have also discovered that methane is a stronger greenhouse gas than carbon dioxide. Why are the atmosphere of the Earth and the atmosphere of Venus so different ? Yet, both planets are roughly the same size ! Venus is a little closer to the Sun than the Earth and its surface and its atmosphere are devoid of any water. Is the atmosphere of the Earth in a fragile balance ? Most moons in the Solar System are devoid of any atmosphere and Titan is really an exception with its dense and deep atmosphere relatively rich in methane.

The image above reveals a portion of Jupiter in its south polar region as well as Saturn's largest moon Titan at scale. One can notice in particular a giant vortex which looks like a typical galaxy, which appears bigger than Titan and which is about the same size as the Red Planet Mars. The original view of Titan was obtained on August 25, 2009 from the Wide-Angle Camera of the Cassini orbiter. The original view of Jupiter displayed online on August 7, 2017 was generated on the basis of data obtained from the Juno probe. Credit for the original view of Titan: NASA/JPL/Space Science Institute. Credit for the original view of Jupiter: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles. Montage credit: Marc Lafferre, 2018.

- To get further information on that news, go to: https://www.space.com/41974-jupiter-titan-methane-global-warming-earth.html and http://advances.sciencemag.org/content/4/9/eaas9593.



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