Methane Anomaly in the Four Corners Region

Methane is one of the major greenhouse gasses, considered to be behind only CO2 and water in terms of warming effect (1). While significantly more effective in increasing air temperature per molecule than CO2, methane is estimated to have caused one third the global warming that CO2 has due to its lower atmospheric concentration and shorter lifespan(1). Total global methane emissions are ~550 TgCH4/year(2), and come from many sources, including energy production/distribution, enteric fermentation (in livestock), coalbed mining, rice production, and landfills(3),(1). Methane emissions are difficult to accurately quantify due partly to numerous natural and antropogenic sources spread through time and space, but being able to accurately quantify emissions is very important for predicting and mitigating effects on climate and air quality as emissions estimates vary widely and are probably largely underestimated(4). The “Four Corners” region of the US (a roughly 2,500 square mile area where Arizona, Colorado, New Mexico and Utah meet) is a major producer of coalbed methane (a method of methane extraction where water is pumped out of a coal deposit and methane trapped in coal seeps out due to the changed pressure gradient and is collected(1)). The San Juan Basin area which is located in the four corners region is the largest source of coalbed methane in the US(4).

A recent article published in Geophysical Research Letters was the product of a partnership between University of Michigan and NASA and seeks to advance space based observations in identifying and quantifying emissions and further and verify observed methane anomalies via high resolution simulations and ground based observations. The researchers (Kort et al) used data collected via a satellite belonging to the European Space Agency which carried Scanning Imaging Absorption SpectroMeter for Atmospheric CHartographY (SCIAMACHY) equipment (this data collection mission began in 2002 and ran until loss of contact with the satellite in 2012)(5). SCIAMACHY data from 2003-2009 showed a “strong source has persisted at Four Corners from 2003 through 2009 in all seasons”(4). Researchers performed high resolution regional simulations with Weather Research and Forecasting Chemical transport model (WRF-Chem) to find what emission rate would be consistent with SCHIMACHY space based observation of the large methane signal over four corners. The emissions rate they found was significantly higher than expected, and showed that Four Corners region emitted 0.59Tg CH4/year in 2003-2009 (almost 10% of total US methane emissions)(4). They note that this new finding is 1.8 times higher than the EPA’s inventory of 0.33Tg/year and 3.5 times previous inventory of 0.168Tg/year by EDGAR (European Commission, Joint Research Centre/Netherlands Environmental Assessment Agency). Kort et al were able to compare their WRF-Chem simulations and spaced based data with data collected from ground based Total Carbon Column Observing Network (TCCON), and so could verify that their modeling of emissions and the signal observed by SCHIMACHY agreed, and that there was indeed a large and previously unquantified methane signal over Four Corners region(4).

An article called “Satellite data shows surprising methane hotspot in US southwest” was published in the Guardian the same week as the Kort paper and seeks to explain the paper’s findings. It begins with an image from the Kort paper showing the methane signal in question. The Guardian’s caption of the image is of note, stating “The Four Corners area (red) is the major us hotspot for methane emissions in the map showing how much emissions varied from average background concentrations from 2003-2009 (dark colours are lower than average; lighter colours are higher)” which might leave some readers, myself included, wishing for a legend to see what units the measurements are in and what concentrations the colors might correspond to (the image is not linked to a source). The article gives a small amount of background on methane, and states that the “hotspot” is not an immediate threat to local residents but does not comment on how that conclusion was reached.  Some of the main quantitative findings of the Kort paper are stated, including a comparison to findings from “Other ground-based studies” which are not referenced or linked, so it is unclear which studies are being referred to. The Guardian article attempts to put findings into perspective for readers by comparing the heat trapping ability of the four corners Methane to that of all yearly CO2 emitted by Sweden, which seemed like a bit of a stretch to me and did not bring much clarity. Also problematic was the communication of the major finding in pounds (“£1.3m a year”) not teragrams, which is a little perplexing as a conversion from pounds to Tg is off by orders of magnitude from the original finding of 0.59Tg CH4/year. 

One positive was a quote from the lead author explaining that their findings are probably due to leaks associated with extraction and transport of methane from coalbeds and not due to fracking, which was not much used in the region during the period of the study- an important point. In one of the stranger sentences, the Guardian states scientists were so surprised by their initial findings “that they waited several years and then used ground monitors to verify what they saw from space”(6) which it turns out is accurate, according to an email to me from the lead author stating team felt they could not publish without ground-level corroboration and were able to use data from a colleague with TCCON to do so. The article ends abruptly with a three-word quote (“That is immense”)(6) from Terry Engelder, “a scientist” who, upon a little googling, seems quite important in the field, but might not be known by the average reader.

I think the Guardian article did a pretty fair job (7/10) of presenting the main findings of the study. The title was a bit too flashy, as the term “hotspot” does not seem to be in regular usage in the literature, and the fact that the methane signal itself was not as surprising as the magnitude and the deviation from previous estimates were. The article does address the large scale of the signal, and attempted (with moderate success) to communicate that to readers. It addressed two of the other key points well- the emissions were probably not from fracking, and the importance of validation of findings with ground-level data, but did not give the reader helpful/necessary information- for example the total amount of methane emitted in the US or world for comparison or any quantification of what’s shown in the image (the article called the methane signal a “red blip”). This probably made it harder for readers to understand findings in a meaningful way.

1.         Baird C, Cann M. Environmental Chemistry. W.H. Freeman and Company. 2012. 736 p.

2.        Cole S and. a9934fd24c11d6dbd8c75fa3ddf04d918435bbd0 @ www.nasa.gov [Internet]. Available from: http://www.nasa.gov/press/2014/october/satellite-data-shows-us-methane-hot-spot-bigger-than-expected/#.WATVHZMrJ0v

3.        Nations U, Convention F, Change C, States U, Protocol M, States TU, et al. Executive Summary. 2014;4(1):1–27.

4.        Kort EA, Frankenberg C, Costigan KR, Lindenmaier R, Dubey MK, Wunch D. Four corners: The largest US methane anomaly viewed from space. Geophys Res Lett [Internet]. 2014 Oct 16 [cited 2016 Oct 16];41(19):6898–903. Available from: http://doi.wiley.com/10.1002/2014GL061503

5.        SCIAMACHY @ en.wikipedia.org [Internet]. Available from: https://en.wikipedia.org/wiki/SCIAMACHY

6.        satellite-data-shows-surprising-methane-hotspot-in-us-southwest @ www.theguardian.com [Internet]. Available from: https://www.theguardian.com/environment/2014/oct/10/satellite-data-shows-surprising-methane-hotspot-in-us-southwest