On July 5th, NOAA ESRL released the preliminary April 2018 global mean CH4 concentration. This month's concentration reached 1858 ppb, which is 10.2 ppb above April, 2017. It is also the second consecutive month with increases above 10 ppb, since June, 2016.
What is troublingly different is that June 2016's increase was still associated with the 2015-2016 El Nino. The March and April 2018 increases are not. Whether these remain as double digit increases will become clear over the next several months as additional site samples are submitted and tested. If they do, what is significant is that this increase of global methane emissions will be most likely be primarily from anthropogenic sources.
The April 2018 global mean concentration is 13 percent higher than April, 1984. We also are potentially observing an ongoing acceleration of CH4 increase in the atmosphere.
The five and ten year trends of CH4 mean concentration change reveal this global acceleration. The April 2018 mean of 1858 ppb is 45.2 ppb above the same month in 2013. This is the second highest five year change, and is the 12th consecutive month of a five year change in concentration above 40 ppb.
The CH4 mean concentration change since April 2008 is 71.5 ppb. This is the third month in a row of a decadal concentration change above 70 ppb. Again, it is troubling that the only other time we have experienced a ten year change above 70 ppb was in response to the 2015-2016 strong El Nino. This time there is no El Nino affecting this methane increase.
With increases in global natural gas production, increasing fire emissions, and permafrost warming in the Arctic, it is quite likely that this trend will continue into the foreseeable future.
Source: NOAA ESRL: https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/
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