Earth’s Climate Exercise 1 (Methane in the Atmosphere)

Methane is one of many organic compounds that can be found on earth. Known as a colorless, tasteless, and odorless gas, it is produced over time through biological processes creating the natural gas. Next to carbon dioxide, methane is one of the major leading gases contributing to global warming (Saunois et al., 2016). With the Trump administration cutting back on methane emission regulations (Friedman & Davenport, 2019), the potential for a rise in global warming is increased. Methane can be found in various places such as the continental margins, tundra soils, and ice cores. It is important to look back on the levels of methane in the past to understand whether or not the trend being set now is at a dangerous level and what steps can be taken to change that. In addition to, more recognition needs to be shown through the part that geological processes play in climate change (Judd et. al., 2002).

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The record of atmospheric methane extends back past 20,000 years, but earlier than 32 years ago systematic global measurements did not exist (Khalil & Rasmussen, 1987). Primary measurements before then were taken intermittently using bubbles of air trapped in ice to obtain data. When analyzing the levels of methane in the atmosphere and how they are altering over time, it is important to look back onto older data trends relating to methane levels. When arranging these trends it is important to note the uncertainties that come along with them. Uncertainties that are important to recognize while going over these data trends, starts with ages in the ice core. There were uncertainties in correctly labeling the age of ice and the air surrounding the ice that are significant (Khalil & Rasmussen, 1987). The variability of the time it takes to form gas bubbles in the ice is to be noted. Ice core samples are used for the measurement of methane can also contain air from several years rather than a single year, the deeper the core sample the more likely that is to be true. Yearly layers compact and air/air bubbles may form together. Through these records, data shows a consistent level of methane in the atmosphere for approximately 20,000 years or more. Also showing that the concentrations of methane began to increase at a rapid rate during the last 100 to 200 years. The changes in the methane trend coinciding with the change of population and may be caused by agriculture and industrial sources related to the population growth (Khalil & Rasmussen, 1987). Increases in the average concentration of methane over the last century are higher than those that have occurred as long as 1000 years ago.

 The emissions from tundra soil are calculated to contribute around 10% of the global atmospheric methane budget. Containing 15% of global soil carbon, making the methane released from tundra soils an important factor to projected global warming (Whalen & Reeburgh, 1990). Different biological models show that through methanogenesis, warmer climate can increase the methane emissions through the soil. Methanogenesis is the formation of methane through methanogens, which are known for being anaerobic microorganisms (Whalen & Reeburgh, 1990). On the other hand, microbial oxidation of methane is viewed as a potential control on emissions. Microbial oxidation being the process where methane is oxidized with different substances. This anaerobically oxidizes 80% of methane coming from marine sediments (Whalen & Reeburgh, 1990). Soil cores were examined and where methane consumption by core segments were measured. Tracer experiments were preformed to determine methane oxidation and distribution through the core sample. Then experiments were done to evaluate the timescale of equilibrium between the soil and open space for added gasses. Through the data collection, moist soils seemed to consume methane the most rapidly. In non-saturated soils, equilibration to the atmospheric methane was faster than that of microbial oxidation (Whalen & Reeburgh, 1990). Showing in the tundra that lowering the water table as a result of a drier climate will decrease the fluxes of methane and lead to a negative feedback for the atmospheric methane.  The experiments concluded that the oxidation of methane (atmospheric) occurs in oxic soils and is not limited in its diffusion through non-saturated soils, showing that negative feedback is possible.

When methane travels through the ground to the surface it can be trapped in reservoirs, secluded by gas hydrates or escape through mud volcanoes or gas seeps (Judd et. al., 2002). It has become apparently clear that movement of methane is an important continuing process and various evidence shows the migration of methane on continental margins. It has been demonstrated that the fluxes of methane into the atmosphere and at the seabed, are important in terms of global carbon budget. The total annual contribution to the atmosphere is around 16-40 Terragrams of methane (Judd et. al., 2002). The emissions into the atmosphere are affected by eustatic sea-level, ocean floor temperatures, and surface conditions. The geological sources of methane can provide both negative and positives feedbacks in regard to global warming or global cooling. Different cycles are more influential at different stages in the cooling-warming process. Together the geological sources and reservoirs are impacting the speed and direction of global climate change. Geological methane is typically released into the atmosphere/hydrosphere by mud volcanoes and natural gas seeps. An estimated 6.6-19.5 Terragrams or methane per year enters the atmosphere from the continental margins (Judd et. al., 2002). This flux is significant and shows that the geological processes should be a more recognized part of the global carbon cycle.

The Trump administration is currently curbing regulations on methane emissions, promoting drilling on public lands, and pushing for more offshore drilling (Schwartz, 2019). By doing these things, there are a lot of things at stake. Not only are there natural reserves and endangered species being threatened, but the quality of life for the future is too. With these cutbacks on regulations, the earth is opened back up to the increasing addition of methane into the atmosphere. The natural cycles that release methane into the atmosphere have been increasing at a fast rate, but with the setbacks on regulations there is nothing being done to slow that rate down. Without any effort being put into slowing the rate of emissions down it will instead rise and raise global warming to a higher degree.

References

Friedman, L., & Davenport, C. (2019, August 30) Curbs on Methane. Potent Green House Gas to BeRelaxed in U.S. New York Times Retrieved from http://www.nytimes.com

Gornitz, V., & Fung, I. (1994). Potential distribution of methane hydrates in the world’s oceans. Global Biogeochemical Cycles, 8(3), 335-347. (Cited by 280)

Hovland, M., Judd, A. G., & Burke Jr, R. A. (1993). The global flux of methane from shallow submarinesediments. Chemosphere, 26(1-4), 559-578. (Cited by 194)

Judd, A. G., Hovland, M., Dimitrov, L. I., Garcia Gil, S., & Jukes, V. (2002). The geological methane budget at continental margins and its influence on climate change. Geofluids, 2(2), 109-126. (Cited by315)

Khalil, M. A. K., & Rasmussen, R. A. (1987). Atmospheric methane: Trends over the last 10,000 years. Atmospheric Environment (1967), 21(11), 2445-2452. (Cited by 126)

Saunois, M., Jackson, R. B., Bousquet, P., Poulter, B., & Canadell, J. G. (2016). The growing role of methane in anthropogenic climate change. Environ. Res. Lett, 11(12), 12. (Cited by 110)

Schwartz, J. (2019, August 29) Major Climate Change Rules the Trump Administration is Reversing. New York Times Retrieved from http://www.nytimes.com

                  Whalen, S. C., & Reeburgh, W. S. (1990). Consumption of atmospheric methane by tundra soils. Nature, 346(6280), 160. (Cited by 110)