The Unexplained Rise of Methane: A Deep Dive into Atmospheric Mysteries

A robust, intermittent 7-year cycle in atmospheric methane concentration has been detected as far back as the 1850s— but it remains unexplained.

Despite similar amounts of biological sources of methane existing pre-industrially, today’s levels in the atmosphere have skyrocketed. This phenomenon challenges existing assumptions regarding emission dynamics and atmospheric lifetimes.

The quandaries present a significant question: could the primary contributor to increased methane levels be a decline in what destroys methane in the atmosphere, rather than a rise in emissions?

A recently published article in the April 2025 edition of Animal Frontiers Journal highlights some pressing questions surrounding methane emissions that remain unanswered.

After remaining relatively stable for 800,000 years, methane levels in the atmosphere have surged nearly threefold over the last 150 years. This startling rise has prompted alarm over global climate implications, resulting in 158 nations signing a Global Methane Pledge in 2021. The pledge aims to reduce global methane emissions by at least 30 percent from 2020 levels by the year 2030.

However, the reasons behind this rapid accumulation of atmospheric methane are still not well-understood, according to the article authored by Peer Ederer and Taras Iliushyk from the Global Observatory for Accurate Livestock Sciences in Switzerland.

Current modelling fails to adequately explain why methane concentrations in the atmosphere saw a slowdown in increase since the mid-1980s, only to pause for six years between 2000 and 2006 before resuming a record rise—without any corresponding spike in methane emissions.

Image source: Animal Frontiers Journal April 2025

A regime change in methane emissions is evident, yet a convincing explanation for this change remains elusive, as highlighted by the authors.

Between 1900 and 2002, the fractional isotope C13 levels in atmospheric methane increased, indicating a heavier atmospheric methane mix. However, since 2002, these values have seen a rapid decline, raising questions about the sources and processes affecting methane levels.

Image source: Animal Frontiers Journal April 2025

The paper stresses that variations in emission and destruction mechanisms can alter fractionation ratios, suggesting significant changes in atmospheric methane sources or destruction patterns over the last two decades.

The Overlooked 7-Year Cycle: Geological Influences on Methane Levels

The report also introduces a frequently overlooked “7-year cycle” of rising methane concentrations, ascertainable in ice-core data dating back to the 1850s. This cycle seems to have been relevant for at least the past 500 years.

“Since there is no global meteorological phenomenon that exhibits such regularity, there must be a geological impulse impacting atmospheric methane concentrations,” the report posits. Identifying and understanding this geological impulse could reshape existing paradigms around methane fluctuation.

The almost threefold rise in atmospheric methane over the past 150 years is often attributed to increased human-caused emissions. However, this interpretation is not as clear-cut as it seems.

“Historically, as now, a majority of methane emissions were of biological origin. The number of methane-emitting ruminants has remained consistent across global grasslands,” the authors highlight.

Wetlands, rainforests, and excess non-eaten biomass were likely responsible for emitting significantly more methane in the past due to their much larger extents. Furthermore, geological methane emissions were historically minimal, under 5% of total emissions.

While there is an assumption that global methane emissions were lower in prehistoric times, this conclusion results from current atmospheric models, which operate under the assumption that methane lifetime remains consistent—a premise that lacks robust evidence.

“If atmospheric lifetimes were thought to be one-third of what they are today, the same amount of emissions now would lead to lower concentrations in prehistoric times,” the authors suggest, thereby altering the research narrative from emissions to atmospheric lifetimes.

Additionally, the cataclysmic Younger Dryas event, which plunged North America and Europe into a sudden ice age about 12,800 years ago, raises further questions about methane behavior during that period.

The paper methodically critiques current atmospheric methane modeling, pointing out significant gaps in understanding various open variables, fluctuating estimates, and the computational limitations that contribute to broad confidence intervals regarding future methane reservoirs.

The authors advocate viewing the methane cycle as a non-linear system capable of shifting equilibria and reacting disproportionately to slight changes. Thus, it’s possible that increasing methane emissions may not drive rising concentrations, but rather shifts in the mechanisms that destroy methane in the atmosphere.

“Current models cannot rule out the possibility that decreased methane destruction in the tropics—rather than increased emissions—is causing elevated concentrations, perpetuating a cycle of uncertainty,” they conclude.