Rising methane may be a sign that Earth’s climate is part of a ‘terminal scale transition’

Since 2006, the amount of heat-trapping methane in Earth’s atmosphere has been increasing rapidly, and unlike the increase in carbon dioxide (CO₂), the recent increase in methane seems to be driven by biological emissions, not the burning of fossil fuels. This could just be normal variability – a consequence of natural climate cycles such as El Niño. or may indicate that a major shift in the Earth’s climate has begun.

The methane molecule is a much more potent greenhouse gas than carbon dioxide but lasts just under a decade in the atmosphere compared to centuries for carbon dioxide. Methane emissions threaten humanity’s ability to limit warming to relatively safe levels. More worryingly, the rate of methane increase in the atmosphere has accelerated recently. Something like this has happened before: spikes in methane marked transitions from cold ice ages to warm, glacial climates.

Methane was about 0.7 ppm (ppm) of air before humans began burning fossil fuels. Now it is more than 1.9 ppm And it rises quickly. Nearly three-fifths of emissions come from fossil fuel use, agriculture, landfills, and waste. The rest is from natural sources, mainly the rotting vegetation of tropical and boreal wetlands.

Methane is a driver and messenger of climate change. We don’t know why it’s rising so quickly now, but the growth pattern since late 2006 resembles the behavior of methane during large fluctuations in Earth’s climate in the distant past.

Methane Record: 2006-present

In late 2006, methane was released into the atmosphere unexpectedly began to rise. Methane rose rapidly in the 19th and 20th centuries, but leveled off at the end of the 1990s. This rise has been driven by fossil fuel emissions, especially from gas fields and coal mines.

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Imagine accelerating the car with your foot down. The car accelerates but eventually the air resistance equals the engine power and the car reaches top speed. In 1999, methane appeared to reach a similar balance between its sources and sinks. Then in late 2006 the amount of methane in the air Climb up quickly. Even more unexpectedly after five years, the growth rate Faster again. During the 2000s, the rate of growth became faster and even faster than it was during the heyday of the gas leaks industry In the eighties.

Methane in the air has risen rapidly since 2006 — and then it has risen again, and again.
NOAA/Nisbet et al. (2023)And Author introduced

Growth today appears to be driven new emissions from wetlandsespecially near the equator but possibly also from Canada (Beavers are methane factories that pulls Huge amounts of plant matter in the ponds they made) and Siberia. This is a result of climate change: increased rainfall has made wetlands wetter and larger while warmer temperatures have promoted plant growth, providing more decaying matter and more methane. Emissions may be from huge cattle herds in equatorial Africa, India and Brazil as well to rise and rotting waste therein landfills Nearby major cities like Delhi are also important sources.

climate extremes

in the past a few million yearsEarth’s climate flipped over frequently Between long periods of cold glaciers, with ice sheets covering northern Europe and Canada, and shorter warm icebergs.

When each ice age ended, the Earth’s surface temperature rose by up to several degrees Celsius over a few thousand years. Recorded in air bubbles in the ice cores, sharp rises in methane concentrations are the main drivers of these great climate-warming events. With each reversion from a glacier to an interglacial climate, there have been sudden, sharp spikes in atmospheric methane, likely from Expanding tropical wetlands.

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These great climate fluctuations that ended each ice age are known as Terminations. Each has a Roman numeral, ranging from ending IX that occurred about 800,000 years ago to ending IA that started the modern climate less than 12,000 years ago. For example, about 131,000 years ago During the second termination, the British climate suddenly flipped from glaciers in the Cotswolds to hippos drenched in what is now Trafalgar Square.

Terminations take many thousands of years to complete, but many include a creeping onset of warming, and then a very abrupt phase of very rapid climate change that can take century or less, followed by a longer, slower period during which the large ice caps finally melt. In the sudden phase of the great change that brought about the modern climate, Greenland warmed by about 10°C in the meantime few decades. During these sudden phases, methane rises very sharply indeed.

Is something dramatic going on?

Methane fluctuated widely in preindustrial times. But its incrementally rapid growth since 2006 is comparable to methane records from the early years of the abrupt phases of previous termination events, such as the one that dramatically warmed Greenland. Less than 12,000 years old.

A research facility with clouds and a mountain in the distance.
The Mauna Loa Observatory in Hawaii has been monitoring the atmosphere since the 1950s.
Susan Cobb/Associated Press/Alamy photo album

There is already a lot of evidence that the climate is changing. Atlantic currents slowing downand tropical weather regions expansionfar north and south Fast heatingAnd ocean temperature Breaks records and Severe weather It became a routine.

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At the icy ends, the entire climate system rearranges. In the past, this has pulled Earth out of stable Ice Age climates and into warm, glacial regions. But we are already in a warm icy region. It’s hard to imagine what will happen next: summer Arctic sea ice loss, thinning or partial collapse of the ice caps in Greenland and West Antarctica, realignment of ocean currents in the Atlantic, and bipolar expansion of tropical weather circulation patterns. The consequences, both for the biosphere in general, and for food production in South and East Asia and parts of Africa in particular, would be very significant.

There is a lot that can be done in a hurry Stop rising methanePlugging leaks in the oil and gas industry, covering landfills with soil, and reducing the burning of crop waste. Shooting methane messengers won’t stop climate change, which is driven primarily by carbon dioxide emissions, but it will help.

Roman numerals IX through I refer to past great climatic shifts. There is no Roman numeral zero, but then any future termination scale transition will be different—the temperature step from our current interglacial climate to a new, yet warmer future. The methane signal is still not clear, but the question remains: has zero termination started?

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