Evidences of accelerating the increase in the concentration of methane in the atmosphere after 2014: Satellite data for the Arctic

Abstract

European orbital IASI/MetOP-A interferometer TIR radiation data were processed by NOAA for methane profiles and uploaded in a publicly accessible archive. Satellite measurements for the middle and high latitudes of the Northern Hemisphere reveal a concentration growth rate of 4-9 ppbv/year in 2010-2013 and up to 12-17 ppbv/year in the 2015-2016. Global estimates based on surface measurements of NOAA at coastal stations for the same periods show an increase from 5-6 ppbv/year after 2007 to 9-12 ppbv/year last two years. Satellite data allow analyzing the methane concentration both over land and over the Arctic seas in the absence of near-surface temperature inversions. The results of remote measurements are compared with direct aircraft measurements in summer-autumn Alaska during the CARVE experiment. The maximum anomalies of methane (in comparison with a relatively clean area between Scandinavia and Iceland) were observed in November-December over the sea surface along the coasts of Norway, Novaya Zemlya, Svalbard and other regions of the Arctic. Anomalies were insignificant in summer. Over the years, the winter anomalies (contrasts) grew: the maximum rate was recorded for the area to the west of Novaya Zemlya (9.4±3.7) ppbv/year. Above Alaska, the anomaly of methane concentration in summer, when the microbilogical sources are active, increased at a rate (2.6±1.0) ppbv/year. The locations of the maxima of the anomaly around Svalbard correspond to the observed methane seeps from the seabed and the predicted regions of dissociation of methane hydrates. The observed methane acceleration during the last two years does not necessarily indicate a long-term tendency: 2015-2016 was a strong El-Niño period.