Methane: Partner-in-Crime
It’s really not fair to label either carbon dioxide (CO₂) or methane (CH₄) as criminal actors. Their function as greenhouse gases is actually to be applauded; our planet has a nice little insulating layer that has been a boon for life. However, these atmospheric gases are central players in a story of too much of a good thing. Aside from CO₂ and CH₄, the other main greenhouse gases include nitrous oxide and a group of fluorinated gases. With no regard for political affiliation or religious beliefs, these molecules wend their way through various planetary processes, including a stint in the atmosphere where they absorb radiation (i.e., radiative forcing). Without these gases, the Earth could be the cold and lifeless rock of Mars; with too much, the Earth could be the inhospitable cauldron of Venus.
As scientists serve in the role of detectives, sleuthing out the origins and impacts of atmospheric methane, emissions of methane are increasing. The recent discovery of a roiling underwater fountain of methane gas in the East Siberian Sea adds to the growing list of potentially highly destructive greenhouse caches caught up in a loop of global warming. Carbon dioxide is, by far, the largest contributor to climate change and is emitted at far higher levels than methane, which comprises approximately 20% of global greenhouse emissions and 10% of US emissions. On average, methane does not spend as much time in the atmosphere as CO₂, although it is much more effective at trapping heat. Measured as Global Warming Potential (GWP), methane is 25 to 34 times more effective than carbon dioxide in trapping radiation. That means that, although methane constitutes no more than a fifth of greenhouse emissions, it contributes about a third of the resultant warming.
Just as with carbon dioxide, there are many natural sources and sinks for methane, including wetlands; however, human activities are the largest sources and these sources have significantly increased the amount of methane moving through the atmosphere. It has been easier to pinpoint where the extra CO₂ has been coming from, as well as where it is ending up, but the study of methane has been more challenging and surprising.
As can be seen from the figure of global methane emissions, considerable emissions stem from human needs. Methane is emitted during the production and transport of coal, natural gas, and oil, as well as from livestock and agricultural practices, such as the cultivation of rice, and by the decay of organic waste in municipal solid waste landfills and wastewater treatment systems. Natural sources include, among other things, wetlands, volcanoes, wildfires and termites. Although US emissions of methane have been largely stable for the past 20 years, global emissions have been on the rise since pre-industrial times, similar to the case of carbon dioxide. According to the Global Methane Initiative, emissions of methane have increased atmospheric levels from 715 parts per billion (ppb) to over 1,780 ppb as of 2007. That’s a 150% increase, with expectations of methane concentrations increasing an additional 20% by 2030, and with most of the increase coming from solid waste management and the oil and gas sectors.
The relatively short lifetime of methane in the atmosphere means that actions to decrease emissions can have near-immediate effect. In addition, methane gas is an energy source with existing technologies that can capture and utilize it as a fuel. A loss of methane from fossil fuel extraction and processing is not only destructive to the environment, but reflects inefficient production resulting in a loss in profits and utilization as well as a source of odors and safety concerns. Mitigation and capture technologies targeting methane-producing activities have the additional benefit of reducing other pollutants as well as preventing the production of lower-level ozone, which presents with many adverse health effects.
A bridge of methane emissions
Oil and natural gas development is a sizable source of methane, especially with the fracking boom of recent years, amounting to approximately 12% of emissions according to the USEPA. Methane emissions were, however, on the decline from the period of 1990 to 2017 even as oil and gas production increased due to technological measures to prevent or capture releases and leaks. Prior to 2016, methane emitted via venting and flaring had also decreased. Flaring is the intentional burning of natural gas that occurs when drilling for gas progresses faster than pipelines can capture and move the fuel; although the larger fossil companies have indicated some measure of progress on flaring and action on climate, there is some evidence to suggest that their commitment is lukewarm. Methane leaks from pipelines have remained relatively unchanged.
In May 2016, the EPA finalized the first-ever national rule to directly limit methane emissions from oil and gas operations. As we have witnessed in recent years, rules are often made to be broken: the Trump Administration has already made moves to weaken these emission restrictions on public lands per a policy of eliminating “regulatory burdens” that “constrain growth” among other things. It should be noted, however, that the venting and flaring of methane from these activities costs taxpayers an estimated $330 million a year in lost revenue, not to mention adverse effects on health and the environment.
Natural gas is highly questionable as a long-term transitional energy source taking us down a path from a fossil-heavy past to an emissions-free future. The benefits of natural gas over oil and coal has been in its lower profile as a source of greenhouse gases. It should be noted that long-term commitment to fracking has additional concerns regarding contamination of groundwater and the larger startup costs and timeframe of building combined-cycle gas plants that can bolster intermittent renewable energy generation.
It is a growing consensus that use of natural gas as a “bridge” between oil and coal and renewables is a bridge that has already been crossed. Natural gas is currently the fastest growing source of energy in the US, therefore, the environmental costs of fracking may soon overcome the benefits of the lower-emitting fuel. In addition, the point where any greenhouse gas emission source is viable may have been passed as our allowable carbon budget has likely been overdrawn; the better long-term solution is the incentivizing of sustainable renewable sources. It is bad policy to invest heavily in an infrastructure and industry that must be phased out, sooner rather than later, without the intervention of carbon capture and storage technology or a switch to a plant-based biogas.
Bubbles about to burst
Trapped bubbles of methane are often found in the ice of lakes in and around the Arctic region: the gas forms when organic materials such as leaves are degraded by bacteria. The recent discovery by researchers in the East Siberian Sea provided alarming observations of record amounts of methane gas coming from the sea. This fountain of gas was the highest recorded source of methane gas, per the expedition leader, with area atmospheric concentrations at nine times the global methane levels; the scientists could literally see the sea bubbling before their eyes.
The Arctic has been warming much faster than other regions around the world, warming and waking up the sleeping giants of the permafrost and the dormant beds of lakes and seas. Russian scientists have noted at least 7,000 underground permafrost bubbles of methane that could “pop” to the surface at any time. It is estimated that every additional degree of global warming translates into the thawing of one-quarter of the world’s frozen tundra. Thawing permafrost does generate both CO₂ and CH₄, however most of the prior focus has been on the emission of CO₂. Regardless of the gas, permafrost is estimated to contain twice as much carbon as the atmosphere currently holds. It is also surmised that certain types of lakes in the Arctic, called thermokarst lakes, may experience what is referred to as “abrupt thawing”.
Warming of the atmosphere and oceans leads to thawing permafrost which leads to degradation of stored organic matter in the soil which leads to more carbon emissions which leads to more warming which leads to…you get the picture. Losses of greenhouse gases from warming permafrost are not fully captured in current climate assessments and modeling. Frozen tundra covers an area of nearly 9 million square miles in the northern hemisphere where permafrost soils, containing thousands of years of carbon accumulation, can be up to 260 feet thick.
The sediments under the oceans contain a large quantity of methane in the form of methane hydrates, which is an icy structure of methane and water, usually contained in ocean beds near the edge of continents. Tapping these deposits has been of interest to many nations that seek new sources of energy, particularly for countries like Japan and South Korea, but the extraction technology is nascent. Per the USGS, an estimated 99% of this methane ice is held in ocean sediments and the remainder in permafrost: one cubic foot of the ice holds approximately 164 cubic feet of methane gas. Although many believe a catastrophic release of methane from hydrates is unlikely, there is evidence that large-scale dissociation of methane ice has played a part in prior climate-driven events in the Paleocene-Eocene Thermal Maximum (55 million years ago) and the late Quaternary (400,000 to 10,000 years ago).
Researchers have detected the signature of the release of methane more recently from warming ocean sediments that had been locked in place for over 10,000 years. Oftentimes this methane is degraded by bacteria as it is released to the surface of the ocean, but as warming continues the possibility of surplus methane gas reaching the surface grows. There has been some discussion that the presence of the East Siberian Sea methane fountains recently observed may be due to salt water intrusion (sea water) into the thawing Siberian Shelf sediments, presenting a potential new mechanism for destabilizing hydrate deposits. This may pose a problem not only in Arctic regions, but also near ice shelves in Antarctica.
What is particularly alarming is that these abrupt processes and sources are not fully quantified or well understood, are not included in climate projections (although gradual warming of tundra soils is captured in models), and are fueled by positive feedback loops of warming and thawing and warming. Climate models have been largely successful at reflecting the many sources and sinks of carbon, as well as turning this information into accurate future predictions of atmospheric concentrations and resulting global and regional warming and associated impacts. However, there is always a leading edge to scientific research, where unknowns are surmised or lurk unsuspected. It is these unknowns, and the need for actions based on accurate predictions, that foster the need for more research.
We are in a time where both mitigation and knowledge are held back by, in short, greed and ignorance. There is still a large collection of people with a measure of authority and influence who are holding the future hostage; for example, actions taken by the governor of Alaska earlier this year have put much of the US research into the impacts of climate change in the Arctic in question. These actions have consequences that weigh as heavily as the business-as-usual burning of fossil fuels. Methane is only a player in climate change when it is released to the atmosphere, and that is the point where our attention should be placed. These previously latent carbon bombs are starting to activate now, but will only become more of a threat as warming continues, within your lifetime, certainly within the lifetime of younger generations. The global community needs to limit warming to 2 degrees Celsius — we have already achieved one degree warming and have likely locked in 1.5 degrees of warming. The best way, really the only way, to avoid a runaway train of warming is to drop all carbon-based fuels as soon as possible. We cannot control most of these unknown ticking time bombs of warming, but we can attempt to defuse them before they blow.