Wetland methane emissions dominate the natural sources of methane.
Global emissions from natural sources total around 250 million
tonnes each year. Natural emissions of methane can be greatly
affected by climate change and the stability of methane hydrates,
with increasing global temperatures, is a cause of much concern
for some climate scientists.
Energy related and ruminant methane dominate man-made methane
sources. Global man-made methane emissions are estimated to total
about 320 million tonnes each year.
Tropospheric destruction of methane by hydroxyl (OH) radicals
is the dominant sink for atmospheric methane. With stratospheric
destruction and oxidation by soil bacteria, the total sink for
methane is estimated to be between 500 and 600 million tonnes
of methane each year.