Rising methane could be a sign that Earth's climate is part-way through a 'termination-level transition'https://theconversation.com/rising-methane-could-be-a-sign-that-earths-climate-is-part-way-through-a-termination-level-transition-211211In the past few million years, Earth’s climate has flipped repeatedly between long, cold glacial periods, with ice sheets covering northern Europe and Canada, and shorter warm inter-glacials.
When each ice age ended, Earth’s surface warmed by as much as several degrees centigrade over a few millennia. Recorded in air bubbles in ice cores, sharply rising methane concentrations are the bellwethers of these great climate-warming events. With each flip from a glacial to an interglacial climate there have been sudden, sharp rises in atmospheric methane, likely from expanding tropical wetlands.
These great climate flips that ended each ice age are known as terminations. Each has a Roman numeral, ranging from Termination IX which happened about 800,000 years ago to Termination IA which initiated the modern climate less than 12,000 years ago. For example, around 131,000 years ago during Termination II, the British climate suddenly flipped from glaciers in the Cotswolds to hippopotami wallowing in what is now Trafalgar Square.
Full terminations take several thousands of years to complete, but many include a creeping onset of warming, then a very abrupt phase of extremely rapid climate change that can take a century or less, followed by a longer, slower period during which the great ice caps finally melt. In the abrupt phase of the great change that brought about the modern climate, Greenland’s temperature rose by around 10°C within a few decades. During these abrupt phases, methane climbs very steeply indeed....
Methane fluctuated widely in pre-industrial times. But its increasingly rapid growth since 2006 is comparable with records of methane from the early years of abrupt phases of past termination events, like the one that warmed Greenland so dramatically less than 12,000 years ago.
There is already lots of evidence that the climate is shifting. Atlantic ocean currents are slowing, tropical weather regions are expanding, the far north and south are warming fast, ocean heat is breaking records and extreme weather is becoming routine.
In glacial terminations, the entire climate system reorganises. In the past, this took Earth out of stable ice age climates and into warm inter-glacials. But we are already in a warm interglacial. What comes next is hard to imagine: loss of sea ice in the Arctic in summer, thinning or partial collapse of the ice caps in Greenland and West Antarctica, reorganisation of the Atlantic’s ocean currents and the poleward expansion of tropical weather circulation patterns. The consequences, both for the biosphere in general and food production in south and east Asia and parts of Africa in particular, would be very significant