The image below further shows how the anomalies have increased over the years, especially on the Northern Hemisphere; note the wide gaps between anomalies on the Northern Hemisphere (blue) and the Southern Hemisphere (green) over the past few months.
The images, based on AIRS NASA data, were produced by Dr. Leonid Yurganov, Senior Research Scientist, JCET, at University of Maryland - Baltimore County. For further images, see Dr. Yurganov's archive at asl.umbc.edu/pub/yurganov/methane