Losing the Climate War to Methane? The role of methane emissions in the global warming puzzle

Written by Dr. Arvind Ravikumar

There is much to cheer about the recent climate agreement signed last December at the 21st Conference of Parties (COP 21) in Paris, France to reduce greenhouse gas emissions and limit global temperature rise to below 2° C. Whether countries will implement effective policies to achieve this agreement is a different question. Leading up to the Conference in Paris, countries proposed their intended nationally determined contributions (INDCs). These refer to the various targets and proposed policies pledged by all countries that signed the United Nations Framework Convention on Climate Change on their intended contribution to reduce global warming. The United States, among other things, is banking on the recently finalized Clean Power Plan by the Environmental Protection Agency (EPA) – this policy aims to reduce US greenhouse gas (GHG) emissions from the power sector by 26 to 28% in 2030, partly by replacing high-emitting coal fired power plants with low-emitting natural gas fired plants, and increased renewable generation (primarily wind and solar). Electricity production by natural gas fired plants is therefore expected to increase over the next few decades, acting as a ‘bridge-fuel’ to a carbon-free economy. Even though the US Supreme Court recently halted the implementation of the Clean Power Plan, the EPA anticipates that it will eventually be upheld.

A major component of natural gas is methane. This is a highly potent greenhouse gas whose global warming potential (i.e. ability to increase the Earth’s surface temperature through the greenhouse effect) is 36 times that of carbon dioxide in long-term (100-year impact) and over 80 in the near-term (20-year impact). Although carbon dioxide is a major component of US greenhouse gas emissions (see Fig. 1), it is estimated that methane contributes around 10% of the total emissions. Thus, given its significantly higher global warming potential, methane emissions and leakage can potentially erode the climate benefits of declining coal production.

Figure 1: US greenhouse gas inventory (2013) Data from EPA
Figure 1. US greenhouse gas inventory (2013). Source: EPA

Methane emissions are fairly diversified across natural and man-made sources. Figure 2 shows the sources of methane emissions in the US (2013) as estimated by the EPA through its GHG monitoring program. While 50% of emissions can be attributed to agriculture and waste-disposal activities, we can see that about 30% of methane emissions come from the oil and gas industry. Much of this can be attributed to the recent boom in non-conventional or shale gas production through fracking technology. The combination of low natural gas prices and higher demand from the power sector makes it imperative to reduce methane emissions as much as technologically feasible.

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Figure 2. US methane emission by source (2013) . Source: EPA.

Currently, methane leaks occur at all stages of the natural gas infrastructure – from production and processing, transmission to distribution lines in major cities. While the global warming effects of higher methane concentrations are fairly well understood, there is currently little consensus on the magnitude of emissions from the natural gas infrastructure. For example, a recent study found that the average methane loss in all distribution pipelines around Boston was about 2.7%, significantly higher than the 1.1% reported in inventory estimates to the EPA. Another study that was published in the academic journal, Science, showed that various independent measurements of methane leakage rate across the US infrastructure varied from about 1% to over 6%. Climate benefits of switching from coal to natural gas fired power plants would critically depend on this leakage rate.

[…], detailed measurements from the Barnett shale region in Texas showed that just 2% of the facilities in the region account for 50% of all the methane emissions.

To better estimate methane leakage, the Environmental Defense Fund (EDF), a non-profit organization based in Washington, DC, organized and recently concluded a series of 16 studies to find and measure leaks in the US natural gas supply chain. While some of the results are currently being analyzed, much of the data show that conventional inventory estimates maintained by the EPA have consistently underestimated the leakage from various sources. It was shown that the Barnett shale region in Texas that produces about 7% of the nation’s natural gas, emitted 90% more methane compared to EPA estimates. To complicate matters further, until recently, estimates from atmospheric top-down data measured using satellites and aircrafts significantly exceeded land-based bottom-up measurements using methane sensors. On a similar note, detailed measurements from the Barnett shale region in Texas showed that just 2% of the facilities in the region account for 50% of all the methane emissions. Such a small fraction of large emission sources will further complicate direct measurements where typically only a small fraction of the facilities in a region are measured. While the EDF and other studies have been instrumental in our current understanding of methane leaks in the US and its contribution to greenhouse gas emissions, much work is required to understand sources, and most importantly, ways to cost-effectively monitor, detect and repair such leaks.

Aerial footage of the recent natural gas leak from a storage well in Aliso Canyon near LA. The leak is estimated to have released 96000 metric tons of methane, equivalent to about 900 million gallons of gasoline burnt and $15 million worth of natural gas. Source: Environmental Defense Fund, 2015.

Methane leakage in the context of global warming has only recently caught public attention – see here, here and here. In addition to greater awareness in business and policy circles, significant efforts are required to identify economically viable leak detection and repair programs. Currently, the industry standard to detect methane leaks include high-sensitivity but high-cost sensors, or low-cost but low-sensitivity infrared cameras. There is an immediate need to develop techniques that can be used to cost-effectively detect leaks over large areas (e.g. thousands of squared miles). From a regulatory perspective, EPA has released proposed regulations to limit methane leaks from the oil and gas industry. This comes on the heels of the goals set by the Obama administration’s Climate Action Plan to reduce methane emissions from the oil and gas sector by 40 to 45% from 2012 levels by 2025. These regulations require oil and gas companies involved in the entire natural gas life cycle to periodically undertake leak detection and repair procedures, depending on the overall leakage levels. The final rule is expected to be out sometime in 2016.

The success of the Clean Power Plan in reducing greenhouse gas emissions will significantly depend on the strength of the proposed regulations to curb methane leaks. We now have a better estimate of fugitive emissions (leaks) of methane from the US natural gas infrastructure. Concurrently, there should be a greater focus on developing cost-effective programs to detect and repair such leaks. It was recently reported that replacing old pipelines with newer ones in the gas distribution network in a city is effective in reducing leaks, and improving public safety. With a considerably higher global warming potential than carbon dioxide, methane has the potential to erode the climate benefits earned by switching from high emitting coal plants to low emitting natural gas power plants. Ensuring that does happen will take a coordinated effort and commitment from both the industry and government agencies.

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Arvind graduated with a PhD in Electrical Engineering from Princeton University in 2015 and is currently a postdoctoral researcher in Energy Resources Engineering at Stanford University. Somewhere later in grad school, he became interested in the topics of energy, climate change and policy. Arvind is an Associate Editor at Highwire Earth. You can read more about his work at his personal website.

Human Impacts on Droughts: How these hazards stopped being purely natural phenomena

Written by Dr. Niko Wanders

We often hear about droughts around the world including those recently in the U.S. and Brazil, which has threatened the water safety for this year’s Olympic Games. Despite their natural occurrence, there is still a lot that we do not understand fully about the processes that cause them and about how they impact our society and natural ecosystems. These topics are of great interest to scientists and engineers, and of great importance to policy makers and stakeholders.

The elusive definition of a drought

A drought can be broadly defined as a decrease in water availability below levels that are considered normal within a region. This means that droughts do not only occur in warm, sunny, dry countries but can take place essentially anywhere. What makes it hard to come up with a single, precise definition of a drought is that this below-normal water availability can be found at the different stages of the water cycle: precipitation, soil moisture (i.e. how much water there is in the soil), snow accumulation, groundwater, reservoirs and streamflow. Therefore, more useful definitions of drought conditions have to be tailored for specific sectors (e.g. agriculture or power generation) by focusing on the stage of the water cycle that is relevant for them (e.g. soil moisture for farmers, and streamflow for controllers of hydroelectric and thermoelectric plants).

Droughts can cover areas that range from a few thousand squared miles to large portions of a continent and can last anywhere from weeks to multiple years. Normally they start after a prolonged period of below-normal precipitation, sometimes in combination with increased evaporation due to high temperatures. This then causes a reduction in water availability in the soil, which can lead to lower groundwater and river levels as a result of decreased water recharge from groundwater aquifers into rivers. Snowfall is another important factor because it adds a steady release of water resources into streams throughout the Spring. When most of the precipitation comes as rain, it will wash out fast, leaving the Spring with dry conditions once again. The evolution of a drought through the water cycle is called drought propagation and normally takes multiple weeks to several months to take place.

So far this season, El Niño has been bringing some relief to the California drought. The current snow accumulation is above normal which is good news for this drought stricken region. The forecasts for the upcoming months look hopeful and it is likely that California will see some relief of the drought in the coming months. Nevertheless, it will take multiple years before groundwater and reservoir levels are back to their normal conditions, so the drought and its impacts will still remain for at least the coming years.

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Figure 1. U.S. Seasonal Drought Outlook provided by NOAA.
Droughts’ impacts on society

Extensive and long-lasting droughts can accumulate huge costs for the regions affected over time. For example, the ongoing California drought caused $2.2 billion in damage for the year 2014 alone. This is only an estimate of the damage to society in monetary terms, while the severe impacts on the region’s ecosystems are difficult to measure and quantify. As a result of the drought conditions, reservoir storages in most of California are at record low levels and strict water conservation policies have been implemented.

The severity of a drought’s impacts, however, depends greatly on the wealth, vulnerability, and resiliency of the region affected, including the degree to which the local economy and services rely on water. Despite the huge costs of the California drought, the U.S. is more capable of mitigating its effects and eventually recovering from it given the country’s general financial strength compared to many developing nations. According to reports by the United Nations and the Inter-Agency Standing Committee, an estimated 50,000 to 260,000 people lost their lives in the severe 2011 drought in the Horn of Africa, due to the fact that the financial means to provide food aid were not present and outside help started too late.

To have better tools to deal with these extreme events, several government agencies and institutes around the world have created drought monitors to track current drought conditions and to forecast their evolution. Examples are the Princeton Flood and Drought Monitors for Latin America and Africa, the U.S. Drought Monitor and the European Drought Observatory. These websites provide information on current drought conditions, which can be used to take preventive measures by governments and other stakeholders. Additionally, they can be used to inform the general public on current conditions and the need for preventive measures, such as conservation.

Latin American and African Drought Monitors developed at Princeton University
Figure 2. Latin American and African Flood and Drought Monitors developed at Princeton University. Credit: Terrestrial Hydrology Research Group at Princeton University.
The power to affect a drought

Traditionally, droughts have only been thought of as a natural phenomena that we have to endure from time to time. However, a recent commentary in Nature Geoscience that included two Princeton contributors argued that we can no longer ignore how humans affect drought occurrences. For example, when conditions get drier from lack of rainfall, people are more likely to use water from the ground, rivers and channels for irrigation. These actions can impact the water cycle over large areas, affecting the water resources of communities downstream and of the local communities in the near future. In the case of California, the severe drop in groundwater levels has escalated in the last three years due to a combination of the extreme drought conditions and the resulting heavy pumping for irrigating crops. The extra water that becomes available from pumping of groundwater is only a temporary and unsustainable solution that will alleviate the drought conditions in the soil locally for a short period of time. Most of the irrigated water will evaporate and only a small portion will return into the groundwater. In the long run, these depleted groundwater resources need to be replenished to recharge rivers and reservoirs – a process that can take multiple years to decades. Furthermore, extracting groundwater in large amounts can lead to subsidence – a lowering of the ground levels – that can sometimes be irreversible and have permanent effects on future water availability in the region. Thus, through our actions we have the power to affect how a drought develops, making it necessary to rethink the concept of a drought to include our role in enhancing and mitigating it.

Figure 3. On the left: Measurement of recent subsidence in San Joaquin Valley, Photo Credit: USGS. On the right: Measured subsidence in the San Joaquin Valley between May 3, 2014 and Jan. 22, 2015 by satellite, Photo Credit: NASA
Figure 3. On the left: Measurement of subsidence (i.e. lowering of the ground levels) in the San Joaquin Valley during the past three decades, Photo Credit: USGS. On the right: Measured subsidence in the San Joaquin Valley between May 3, 2014 and January 22, 2015 by satellite, Photo Credit: NASA.

But it’s not all bad news. Last year I carried out a study with my collaborator, Dr. Yoshihide Wada, that found that sometimes human interventions can have a positive effect on the impact of natural drought conditions. This is most clear when we look at reservoirs that are built in many river systems around the world. It is shown that by building these structures the river discharge is more equally spread throughout the year. High flows or floods can be dampened by storing some of the water in the reservoirs, while this water can be used in the dry season or during a drought event to reduce the impact of low flows. This in itself opens up opportunities for regional water management that can help reduce the region’s vulnerability to droughts. Three limitations of the reservoirs are that they increase the amount of evaporation by having large surface areas, their benefits are limited in prolonged drought conditions simply because their storage is not infinite, and finally, they have a large impact on plants and animals in the downstream ecosystems (e.g. migrating fish species that need to swim upstream).

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Figure 4. Impact of human intervention on future hydrological drought, as a result of irrigation, reservoir operations and groundwater pumping. Darker colors indicate higher levels of confidence (Figure adapted from Wanders and Wada, 2015).
Drought in the future

Scientist have carried out many studies to explore what will happen to the characteristics and impacts of droughts in the future. Multiple research publications show that droughts will most likely increase in severity compared to the current conditions in many of the world’s regions with projected increases in human water demand, painting a stressful future. This then requires an adjustment in the way we deal with drought conditions, how we monitor and forecast these extremes, and how we consume water in general.

A short-term solution is trying to improve our monitoring and forecasting of these events so that we are better prepared. For example, additional improvements in meteorological and hydrological forecasts for conditions 3-6 months in advance would help operators manage their reservoirs in a way that would reduce the impact of upcoming drought events. These improvements require scientists to become more aware of the impact that humans have on the water cycle, which is a growing area of interest in recent years, but is definitely not standard practice.

Apart from increasing our possibilities to forecast upcoming drought events, we could also change our response to ongoing drought conditions by trying to be more efficient with the remaining available water. This could be achieved by using more efficient irrigation systems, building separate sewage systems for rainwater (that could be used for drinking water) and domestic and industrial wastewater (that is only reusable after severe treatment), and not cultivating crops that have a high water demand in areas with a natural low water availability. All these measures require long-term planning and willing government agencies and societies that would like to push and achieve these goals. Often a severe event (with significant damage) is needed to create the necessary awareness to realize that these measures are a necessity, such as the case in California that has resulted in new water laws and in Australia a few years ago.

Humans and the natural water system are strongly intertwined, especially in hydrological extreme conditions. Our impact on the water cycle is significant and cannot be neglected, both in normal conditions and under extreme hydrological ones. It will be important in the coming decades for us to learn how to responsibly manage our valuable water resources within a changing environment.

 

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Dr. Niko Wanders is a Postdoctoral Research Fellow in the Civil and Environmental Engineering Department at Princeton working together with Prof. Eric Wood. His research interests include the study of the physical processes behind droughts,  as well as the factors that influence their magnitude and impact on society. Niko received a NWO-Rubicon Fellowship to work on the development of a global sub-seasonal drought forecasting system. The aim of the project is to develop a system that cannot only forecast upcoming drought events, but also make reliable forecast on the drought impact on agricultural production, water demand and water availability for human activities.

A Precarious Puzzle of Expanding Deserts: How arid Asia has varied over time and the confusion over recent desertification

Written by Jane Baldwin

Inner Mongolia (Nei MengGu in Mandarin Chinese) lies right at the border of the nation of Mongolia within mainland China (see Figure 1). Pictures of yurts, traditional pony races, Mongolian wrestlers, and most of all rolling grasslands attract many Chinese tourists to this region each year (see Figure 2). In summer 2009, while I was an undergraduate studying Mandarin Chinese in Beijing, I also became enticed to this region. Tasked by my program to use my newly polished Mandarin to conduct a “social study” in an area outside Beijing, Inner Mongolia seemed both a very foreign and fascinating locale to investigate.

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Figure 1. Inner Mongolia, a Chinese province, lies just south of the nation of Mongolia. It is part of the arid lands that stretch across interior Asia. Source: adapted from Nasurt, 2011.

A group of my classmates and I took an overnight train from Beijing to Hohhot, and then a bus far into the countryside to our first yurt encampment. As expected, the great expanse of the scenery was stunning—the landscape stretched out before us only punctuated by occasional small hills, yurts, and sheep. However, we were shocked to discover the lush grasses in pictures were reduced to dry scrub only an inch or two high (see Figure 3).

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Figure 2. The Inner Mongolian pastoral ideal branded by Chinese tourist agencies. Source: http://www.chinadaily.com.cn/m/innermongolia/2015-04/10/content_20401697.htm
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Figure 3. The state that many grasslands in Inner Mongolia are currently in or approaching following recent desertification. Source: http://www.theguardian.com/world/2015/apr/10/inner-mongolia-pollution-grasslands-herders

I was concerned by this difference, and decided to focus my interviews with the local people on these environmental changes. The local nomadic herders informed me that desertification (or shamohua in Mandarin—literally translated as “change into desert”) had become a serious issue in this region over the past 20 years or so. One herder I interviewed recalled that as a teenager, the grasses had reached as high as his horse’s flank, while now they extended no higher than his horse’s hoof. These observations led me to wonder many questions which did not yield firm answers through my interviews: What was the cause of these dramatic changes? Were the local people responsible for the degradation? Or was it caused by larger scale climate variations outside of their control? And what would be the appropriate policy response to deal with the degradation and still respect the people who had lived there for generations?

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Since that summer, this suite of questions around deserts and desertification has inspired much of my study and research, both as an undergraduate and now a PhD candidate in Atmospheric and Oceanic Sciences. My PhD research focuses broadly on understanding the climate of arid and semi-arid regions across Asia that define the margins of these grasslands (see Figure 1). As the largest deserts outside the tropics, this region presents a number of interesting climate dynamics questions. However, through research, classwork, and personal reading I have also sought to understand this region from a variety of angles beyond climatological, in particular geological, historical, and political. While spiraling in towards the desertification question, I have developed a mental narrative for this region, and its changes and controls of its climate over different periods of time.

Observing sediments and fossils, geologists have pieced together a record of arid Asia that shows this region to have varied greatly over the long geological timescales of millions of years. 50 Ma (million years ago), what is now Central and northern East Asia was covered in warm, damp forest populated by ancient horses, and rhino ancestors larger than modern elephants. A few theories exist for what spurred the relatively rapid (few million year-long) transition to the cool, dry climate we know today. Around this time India’s collision with the Eurasian subcontinent was creating the colossal Tibetan Plateau and Himalayas. The longest running theory for the formation of these deserts is that this newly risen topography blocked moisture from reaching Central and northern East Asia, drying this region. Climate modeling studies have indeed indicated that the Tibetan Plateau creates significant aridity outside the tropics in Asia . However, new research presents an alternative theory for the formation of this region. A large inland sea on the western margin of Central Asia, called the Paratethys, was recently found to have retreated just prior to the transition of this region to an arid environment; the migration of this moisture source may have played a dominant role in drying Central Asia. Which of these mechanisms (Tibetan Plateau uplift or the retreating Paratethys) was most important for the drying of Asia, and whether they might be linked, are both still open and actively researched questions.

More recent environmental history (i.e. the past few thousand years) is recorded in tree rings. When trees are water-stressed, how much their trunks grow radially depends in large part on how much rainfall there is. Widths of tree rings thus provide a proxy for historical drought/wet periods. The dry climate of this region over the past few thousand years, and its variations in precipitation recorded in these tree rings are hypothesized to have played key roles in human history, with the most dramatic example being the expansion of the Mongol Empire. Genghis Khan and the nomadic steppe tribes allied with him relied on horses for travel, sustenance, and warfare. Tree rings suggest that during the 13th century when the Mongol Empire expanded to cover China, Central Asia, and parts of the Middle East and Europe, the region was warm and persistently wet; these climatic conditions favored high grassland productivity, supporting Mongol political and military power during this critical period. This is but one example of how climatic and historical changes link tightly in this water-stressed region.

Over the past hundred years, the clearest climatic trend on the global scale has been warming caused by anthropogenic carbon emissions, primarily CO2 released from burning fossil fuels. How this global signal will translate to the regional scale is still a topic of active research in the climate science community. The most recent UN Intergovernmental Panel on Climate Change (IPCC) report shows that warming is clearly predicted over Asia as carbon emissions continue to increase. However, there is little consensus among climate modeling studies regarding how precipitation will change over arid Asia. This uncertainty is concerning for an environment that is already exhibiting symptoms of increasing water-stress. Desertification or land degradation has occurred across the margins of arid Asia over the past few decades, including places as diverse as the former Soviet countries that exist in the Aral Sea drainage basin, Qinghai Province on the Tibetan Plateau, and of course Inner Mongolia. While the UN Convention to Combat Desertification has motivated countries to submit plans to fight this degradation, on-the-ground action has been slow and limited. Facing the double threat of ill-planned development and global warming, these delicate regions on the border of Asia’s great deserts are currently in a precarious position.

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While my understanding of arid environments and particularly their variability has increased significantly since I first visited Inner Mongolia in the summer of 2009, the recent desertification of this region is still a puzzle for me and for the scientific community at large. Over the past decade, the Chinese government has tried a number of strategies to deal with the desertification in Inner Mongolia. Citing overgrazing as the cause of the increased aridity, the government has resettled pastoralist nomads into cities—nomads who have grazed the steppe for thousands of years. Since 2003, the total number of urban resettlements in Inner Mongolia is 450,000. Meanwhile, in the tradition of the great engineering emperors of yore, the Chinese government is supporting a “Great Green Wall” of trees planted to halt the expanding desert and decrease dust transport. By the project’s planned end in 2050, it is intended to stretch 4,500km (2,800 miles) along the edge of China’s Northern deserts, covering 405 million hectares—a truly massive endeavor.

Unfortunately, without knowing the root cause of the desertification or how this region will respond to ongoing global warming, it is difficult to predict whether these policies are appropriate. While the Chinese government points its finger at overgrazing, some experts believe that it was the government’s prior actions in this region (fencing land and supporting agriculture over pastoralism) and ongoing mining pollution that has pushed this region away from a sustainable equilibrium and towards desertification. Adding flame to the fire, ecologists and hydrologists wonder whether the Great Green Wall’s trees will grow successfully or just deplete the water supply further. Meanwhile, recent climate studies provide an alternative explanation to these land-use centric arguments, suggesting that non-local climatic causes such as global warming and decreasing East Asian monsoon strength may explain the increasing aridity.

In this quagmire of rapid environmental change and scientific uncertainty one thing is clear: it is critical for there to be a robust dialogue between scientists and policy makers for Inner Mongolia, and the dry climates in Asia at large, to have a chance at developing sustainably.

 

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Jane is a PhD candidate in Princeton’s Atmospheric and Oceanic Sciences program in joint with NOAA’s Geophysical Fluid Dynamics Laboratory, where she is advised by Dr. Gabriel Vecchi. Her research employs a combination of dynamical climate models and earth observations to elucidate the ties between global and regional climate, and move towards useful predictions of climate change at regional levels.