Before wanting to reduce emissions of greenhouse gas in particular, it is necessary to know the sources and the dynamics. This is what NASA researchers hope to do with a new 3D model that sheds light on the movements of methane in our atmosphere.
Methane (CH4). According to experts, this gas is responsible for 20 to 30% of the temperature increase recorded to date in the context of global warming. And researchers from NASA (United States) are today presenting a new 3D tool intended to visualize the diversity of sources of this powerful greenhouse gas and to track its concentrations and its movements in the atmosphere.
Remember that the global warming potential (GWP) of methane is 25 times greater than that of CO2. And that the sources are numerous. Methane is emitted when fossil fuels such as coal, oil or gas are used. But the oceans also emit methane. Just like wetland soils or agriculture. Rice cultivation, in particular, as well as animal husbandry. Overall, "it is estimated that up to 60% of the current methane flow from the earth to the atmosphere is the result of human activities," said Abhishek Chatterjee, researcher, in a NASA statement. But it remained difficult for scientists - due to a lack of measurement and understanding of feedback phenomena - to predict future trends.
To solve this problem, NASA researchers collected data from emission inventories, field campaigns and even satellite observations. Data they have injected into a model that also estimates emissions from known natural processes. And which also simulates atmospheric chemistry which breaks down methane. Then they added a meteorological model to visualize the path of methane in our atmosphere.
A wide variety of methane sources
The proposed 3D visualization highlights the complexity of the question. It illuminates the movements of methane in the atmosphere according to the landscapes and the seasons. It also shows that high altitude winds can transport methane very far from its sources. It also highlights some specific regions in this area.
Thus 60% of methane emissions come from the tropics. Particularly because the Amazon basin and its wetlands seasonally create, when flooded, an environment low in oxygen and therefore favorable for emissions.
Europe, on the other hand, seems rather preserved. It is the only region that has experienced a decrease in emissions over the past 20 years.
In India, rice and livestock are the main sources of methane emissions. And it is mainly the management of livestock and agricultural waste that currently results in the region, an increase in emissions of 1.5% per year. More generally, in Asia, more than 85% of methane emissions are due to human activities.
Conversely, in the Arctic, more than 70% of emissions are of natural origin. But high latitudes still appear to be responsible for 20% of total emissions. And researchers are concerned about the greenhouse gases that warming soils could release into the atmosphere.
WHAT YOU MUST REMEMBER
Methane is a powerful greenhouse gas.
NASA today offers researchers a new tool for studying the behavior of this gas in our atmosphere.
It already reveals some great patterns.
Regards
Relative effectiveness of CH4 and CO2 in greenhouse warming depends on how one makes the comparison. One way to do this is by using warming models (e.g. MODTRAN) and past atmospheric increases in both gases. Over 1984-2019, CO2 increased by relative 20% and CH4 by relative 14%. If we assume a similar future increase for each, say by 20% (over any time period), then the additional warming produced by CH4 would only be one-fourth as large as that from CO2. The IPCC fourth assessment report (2007) gives similar relative values.
The relative warming effectiveness of CH4 compared to CO2 is often inflated due to assumptions made about their concentration increase. For example, a 1 ppm increase in CO2 would produce no measurable warming, whereas a 1 ppm increase in CH4 would. An equal concentration increase (say each by 10 ppm) is often the assumption. But past increases have been more proportional, as from 1984-2019.
Dear Donald,
Thank you for your profound comment, with which I totally agree.
Regards
Dear Bachir
CH4 global concentrations seem to have stalled during the 2000-2008 period (see attached figure). However, since about 2008 up to now, rising CH4 have re-appeared likely due to an explosion and popularity of wells associated with hydraulic fracturing. Therefore, best practices should be put in place to limit the emissions of CH4. Since CH4 has a long lifetime and is well mixed within the boundary layer, it is difficult to trace it back to sources. It is suggested that a marker for anthropogenic CH4 is to use ethane and propane as a proxy. Those are anthropogenically produced and associated with methane.
More details in my paper
An overview of selected emerging outdoor airborne pollutants and air quality issues: The need to reduce uncertainty about environmental and human impacts
- January 2020, Journal of the Air & Waste Management Association (1995) 70(1), DOI: 10.1080/10962247.2020.172373
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