I am an agnostic when it comes to global warming, but the source the global warming folks would point to for a spike in methane are found in nature and would be released at higher and higher rates as (if) global temperatures rise.
The two prime examples are the peat locked up in permafrost and seabed hydrates. A release from peat might follow a North South trend. A release from seabed hydrates probably would not.
Release from hydrates under the north polar ice cap do to very large quantities of hydrate being there, and a substantial increase in the northernmost mid atlantic rift volcanic activity heating it up enough to “burp”.
Huge nearly pure methane bubbles have been found under the icepack near greenland...