Methane emissions have been increasing steadily since the start of the industrial age. Atmospheric levels of methane are now 2.5 times pre-industrial levels. The current rate of methane emissions would see global temperatures increase by 4.3 °C by 2100 (Jackson et al. 2020).
Sources of Methane
Methane is produced by the breakdown or decay of organic material and can be introduced into the atmosphere by either natural processes – such as the decay of plant material in wetlands, the seepage of gas from underground deposits or the digestion of food by cattle (enteric fermentation) – or human activities – such as oil and gas production, rice farming or waste management.
NOAA Global Monitoring Laboratory
A pie chart provides important information but doesn’t provide any information about emerging trends.Emissions
The 2022 methane increase was 14.0 ppb, the fourth-largest annual increase recorded since NOAA’s systematic measurements began in 1983, and follows record growth in 2020 and 2021.
Global Climate Change Retrieved December 20, 2023, from NASA
The extended time scale in the preceding graph hides an important point. Examine the following graph and pay specific attention to the time between 1999 and 2006:
Global Climate Change Retrieved December 20, 2023, from NASA
Methane concentrations were rising quickly in the 80s and 90s, relatively stable between the 1999 and 2006 and then started to rise quickly again in 2007. Neither the 1999 - 2006 plateau nor the increase starting in 2007 were expected.
During the period of relative stability methane emissions from fossil fuels dropped dramatically. While the data don't point to a specific cause the drop's timeline corresponds to the breakup of the Soviet Union and a significant drop in natural gas production there. Poor production technology and massive leaks from long pipelines led to significant emissions. The introduction of western technology after the breakup has significantly reduced emissions.
Since 2007 the growth in methane concentration has been seen across the globe. Emissions are rising in both the Arctic and Antarctic. Growth rates are above average in the tropics and northern midlatitudes (Nisbet et al. 2019). Atmospheric data strongly suggest a rise in microbial emissions is the primary driver (up to 85% of the increase) of the post 2007 methane growth with the largest contribution coming from the tropics (Basu et al. 2022). Potential sources for the rest of the increase include increased emissions from fossil fuel production and use and a reduction of the rate at which the atmosphere breaks down methane.
Major sources of microbial emissions include wetlands, livestock and waste. Wetlands are warming and flooding due to increased precipitation means they’re getting larger. Both factors result in increased methane emissions. Warmer, wetter weather usually creates better conditions for wildlife which means their populations — and emissions — increase.
The implication is that the consequences of warming are leading to more warming. It’s too early to say this is a feedback loop. Early evidence is, however, of concern. As described in the “Good News” section a rapid reduction of emissions would have a dramatic impact and could help to avoid runaway effects.
References
After 2000-era plateau, global methane levels hitting new highs
Basu, Sourish, Xin Lan, Edward Dlugokencky, Sylvia Michel, Stefan Schwietzke, John B. Miller, Lori Bruhwiler, et al. “Estimating Emissions of Methane Consistent with Atmospheric Measurements of Methane and δ 13 C of Methane.” Atmospheric Chemistry and Physics 22, no. 23 (December 5, 2022): 15351–77. https://doi.org/10.5194/acp–22–15351–2022.
Jackson, R B, M Saunois, P Bousquet, J G Canadell, B Poulter, A R Stavert, P Bergamaschi, Y Niwa, A Segers, and A Tsuruta. “Increasing Anthropogenic Methane Emissions Arise Equally from Agricultural and Fossil Fuel Sources.” Environmental Research Letters 15, no. 7 (July 1, 2020): 071002. https://doi.org/10.1088/1748–9326/ab9ed2.
Lan, X., S. Basu, S. Schwietzke, L. M. P. Bruhwiler, E. J. Dlugokencky, S. E. Michel, O. A. Sherwood, et al. “Improved Constraints on Global Methane Emissions and Sinks Using δ 13 C‐CH 4.” Global Biogeochemical Cycles 35, no. 6 (June 2021): e2021GB007000. https://doi.org/10.1029/2021GB007000.
Nisbet, E. G., E. J. Dlugokencky, M. R. Manning, D. Lowry, R. E. Fisher, J. L. France, S. E. Michel, et al. “Rising Atmospheric Methane: 2007–2014 Growth and Isotopic Shift.” Global Biogeochemical Cycles 30, no. 9 (September 2016): 1356–70. https://doi.org/10.1002/2016GB005406.
Saunois, Marielle, Philippe Bousquet, Ben Poulter, Anna Peregon, Philippe Ciais, Josep G. Canadell, Edward J. Dlugokencky, et al. “The Global Methane Budget 2000–2012.” Earth System Science Data 8, no. 2 (December 12, 2016): 697–751. https://doi.org/10.5194/essd–8–697–2016.
Saunois, Marielle, Ann R. Stavert, Ben Poulter, Philippe Bousquet, Josep G. Canadell, Robert B. Jackson, Peter A. Raymond, et al. “The Global Methane Budget 2000–2017.” Earth System Science Data 12, no. 3 (July 15, 2020): 1561–1623. https://doi.org/10.5194/essd–12–1561–2020.
No comments:
Post a Comment