Methane levels are soaring
The graph shows how methane levels in the atmosphere have moved over the last 802,000 years.
- Each section on the timeline is 100,000 years.
- Methane moved between 400 and 600 parts per billion (ppb) for about 700,000 years.
- It skyrocketed from about 700 ppb to 1,800 ppb from the beginning of the industrial revolution in about 1750,
This is concerning as methane is about 25 times more potent as a greenhouse gas than carbon dioxide.
Tracing released methane is not simple as there are many sources of methane, including swamps, rivers, volcanoes, bushfires, digestive microbes in cattle, gas wells and pipelines, oil wells, coal mines, rubbish dumps, sewage treatment and rice fields.
The permafrost methane feedback loop.
Diagram: The Permafrost Methane Feedback Cycle
There are vast quantities of methane trapped in the Arctic permafrost, and global heating is thawing this permafrost. The thawing releases the trapped methane, adding to the greenhouse gases in the atmosphere. This can form an amplifying feedback cycle as:
- An increase in temperature melts permafrost
- This releases methane
- This increases the greenhouse gases in the atmosphere.
- This increases global temperatures.
Note that this feedback is not reversible. A decrease in temperatures might regenerate the permafrost, but the methane has escaped into the atmosphere. The cooling would not decrease methane in the atmosphere, and so decrease global warming.
Permafrost is ground that is normally permanently frozen. But climate change has caused permafrost to melt at an unprecedented rate. The ground buckles and sinks, causing trees to lean and fall.
Permafrost covers a vast area. Surprisingly, nearly a quarter of the ice free land in the northern hemisphere has permafrost underneath it. There is about twice as much carbon in this permafrost as currently in the atmosphere.
Thawing permafrost has caused severe
The Earth’s methane levels are rising and we do not know why
(New Scientist: May 2019)
The current warming could lead to methane release dominating our climate, and spiralling global warming, even if humans stopped burning fossil fuels.
Updated: 23 August 2019