This blog is compiled and edited by Shashank Kumar Anand (Associate Editor, Highwire Earth; Graduate Student, Department of Civil and Environmental Engineering, Princeton University). It is based on the work of Sara Cerasoli and Amilcare Porporato that appeared in the Journal of Hydrology early this year (See the peer-reviewed article here)
In the 1920s, Charles Ponzi gained notoriety for running a fraudulent scheme that now bears his name. Imagine a magic trick where someone promises to turn a small amount of money into a fortune in no time. This sounds amazing, right? Well, that is the trick a Ponzi scheme plays – except it is not magic; it is deception.
Here is how it works: Imagine you meet someone who says they have a fantastic investment opportunity. They say that if you give them $100, they will double it in just a few weeks. That sounds like an incredible deal, doesn’t it? You might think, “Why not? I will get back $200 so quickly!”
Now, to make this trick seem real, the person might even show you some “proof” by giving you $200 after a few weeks. But here is the trick – that $200 did not come from any real investment or profit. Instead, they used money from new people who joined the scheme after you. So, when new folks give them $100 each, they use that money to pay you back. It looks like you made a profit, but they just used someone else’s money to do it.
This is where the trick gets tricky. People who got paid back tell their friends and family about this amazing investment. More people join, each giving their money, and they are also paid with money from the newcomers. This cycle continues, with the person at the center collecting money from new members to pay off the earlier ones. It creates an illusion of profit and success, and more people become attracted, hoping to get rich quickly.
Now, if one starts thinking about this cycle of the Ponzi scheme, it is unsustainable as it relies on an ever-growing number of new members to keep paying off the earlier ones. But as more people join, there comes a point where it is impossible to find enough new members to cover the payments. When that happens, the scheme collapses. The person running the scheme might disappear with whatever money is left, leaving many people who invested with nothing but empty pockets. This can be seen as “an example of market failure with an unsustainable economic trajectory”.
Cerasoli & Porporato draw a parallel to this investment fraud with groundwater extraction, in which over-exploiters of groundwater from past generations play the role of the early investors, profiting from excessive overdraft and gaining in terms of higher agricultural productivity simply because more water input results in more agricultural output. But if one thinks about the next generation, this over-extraction of water will eventually leave more and more depleted aquifers for the next generation (the late investors). This means that if we only focus on the short-term benefits of maximizing agricultural output for a few years, in the long term, we might be on an unsustainable path that can only end with the exhaustion of the water resource. Using the case study of Kern County in California, the authors suggest that we might be in a Ponzi scheme of groundwater extraction. This finding resonates with the news that we have been hearing regarding the Central Valley groundwater depletion crisis (1,2). Just imagine how many more Kern County we might have around the world that we may not know of!
The original Ponzi scheme collapsed after nine months. In that sense, we are fortunate that aquifer dynamics operate on much longer time scales, giving us time to take timely action. The question hence arises: what can be done to ensure that we get out of this dangerous path? The authors suggest that there can be two different policy approaches based on their optimality framework of groundwater extraction.
The hard policy scenario assumes that state/federal regulations immediately reduce pumping rates to a value lower than the natural recharge. On the environmental side, the plus is a speedy recovery of water tables. The cumulative profit over several decades from the hard policy path is the highest. Still, the challenges are obviously human adaptation, which does not seem plausible, and at the same time, the investment to make that change now may not be very practical.
The soft policy option is a more realistic approach to tackle the Ponzi scheme of groundwater extraction. Pumping rates are gradually decreased by some percentage, say 5% of current values each year until they reach the long-term sustainable pumping rate by some year, say 2040 so that we reach the long-term sustainable path slowly but eventually.
Whether we will manage to escape this scheme is a question that can only be addressed if we first realize that the short-term gain can hurt in the long term. The challenge also arises because the best, or rather, the long-term optimal way of extracting groundwater will result in initial lower gains. To safeguard the interests of future generations, it will require us, to avoid being our own Ponzi.
Authors of the scientific publication:
Sara Cerasoli is graduate student from the Department of Civil and Environmental Engineering at Princeton University
Prof. Amilcare Porporato is affiliated with the Department of Civil and Environmental Engineering and High Meadows Environmental Institute at Princeton University.
In the US, the fight against climate change often looks more like a fight to achieve the public recognition that climate change is real. Flat out denial of science by the dominant strain of conservative politics and the reticence to take bold action on the part of moderates, combined with the self-interested, well-funded and short-sighted survivalist instinct of the fossil fuel industry, continues to hamper sustainable development in our country. We stagnate at home even as we attempt to export models for sustainable development to other parts of the world.
In our national culture, broadly speaking, we still uphold the rugged cowboy individual as the model for how to exist in the world. Recently, researchers at the University of Virginia pointed out the degree to which Americans’ individualism hindered our collective response to the coronavirus. Lately, science and individualism haven’t seemed able to get along.
A good cultural marker for this is country music. In the US, recent years have given us country songs like “Coal Keeps the Lights On” by Jimmy Rose (championing a phrase that has been used widely in the coal industry’s propaganda campaign) and “Coal Town” by Taylor Ray Holbrook (the music video for which was produced in partnership with the United Mine Workers of America). It is worth noting that these artists are rather marginal country artists, both little known and both hailing from Appalachia, but have taken on specific significance in the debate around the political and cultural value of coal. More widely popular country music artists, at least those that produce popular music that is marketed as “country,” eschew the specifically political in favor of a few main themes: booze, romance, and general patriotism (guns, religion, troops, sports, farming, hunting, the paterfamilias, etc.). The wildly popular band Florida Georgia Line, in their summer 2020 hit “I Love my Country”, exalts the use of styrofoam plates while rattling off a list of American stuff: “Barbecue, steak fries / styrofoam plate date night.” It seems that, regarding sustainability, American country music either takes a hard pro-fossil fuels stance, or nonchalantly implies approval of the status quo. As far as the market is concerned, apathy towards climate change reigns. This is not entirely surprising, given the political climate.
What is surprising is how the analogous genre in Mexico, música regional, compares. Many of the themes heard in contemporary American country music are still present, both the good (importance of family, romantic love), the bad (binge drinking, misogyny) and the more complicated (guns, dogmatic religion). Mexican country music is even starting to incorporate Latin hip-hop and pop into their music, similar to how bands like Florida Georgia Line imitate rap lyricism in their own vocals. This all makes sense; to paint with broad strokes, it’s safe to say that Mexican society and cowboy culture developed in a manner parallel to the development of their American counterparts, and pop musical trends, such as the increasing relevance of hip-hop forms across the boundaries of genre, are increasingly global phenomena. However, Mexican country music, despite its conservatism, finds it within itself to engage with climate change.
At approximately the same time Florida Georgia Line was working on “I Love my Country”, Edén Muñoz, the lead singer of the Mexican group Calibre50 (“50-Caliber”) was working with fellow artists Alfredo Olivas, la Arrolladora Banda el Limón (“the Irresistible Lemon Band”), Pancho Barraza and C-Kan on a song called “Corazón Verde” (“Green Heart”). The song amounts to an impassioned plea for the listener to become conscious of climate change, understand how it is detrimental to human society, and actually do something about it. Pancho Barraza sings: “Estamos cavando nuestra propia tumba / y no es por asustarlos, viene lo peor” (We are digging our own grave / and not to scare you, but the worst is yet to come”). He goes on: “Falta de conciencia y no es coincidencia / que todos los días haga más calor” (“[There is] lack of awareness, and it’s no coincidence / that every day it gets a little bit hotter”). Tough solutions are not proposed, just tough rhetoric about what is happening right now. The music video shows the artists planting trees (which is more symbolically important than it is effective as a long-term strategy). Still, it’s a fine start, at least rhetorically.
Perhaps most importantly, the artists express concern for future generations: “¿Para qué esperarnos? Limpiemos el mundo / y cuidemos la casa. O ya se preguntaron / a tus hijos y a los míos / ¿qué les vamos a dejar?” (“What are we waiting for? Let’s clean up the world and take care of our home. Or have you already asked yourselves what’s going to be left for your children and mine?”). In the words of the singers, recognizing and fighting climate change is an urgent civic duty. The fact that this urgency is absent from cultural representations of American patriotism is baffling.
I mention this song not to hold up Mexico as an exemplar of environmental or cultural sustainability, or as an example of a society that always leverages science to increase the public good. Certainly, in the context of the coronavirus pandemic, Mexico has hardly stood out as successful in its response. What’s more, these artists don’t exactly have a blank check to claim the moral high ground on whatever topic they choose. The same artists that here sing about making cultural and political shifts to fight climate change also sing in a glorifying way about guns, corruption and cheating on their wives and partners. I make this comparison between American and Mexican country music to illustrate that, outside of the US, even politically conservative cultures and ideologies elsewhere pass the very low bar of urgently believing in science. It is a bar that the US needs to pass soon. Coal may “keep the lights on” for now, but it will eventually burn down the house.
Ashford King is a PhD student in Spanish and Portuguese at Princeton University. He is also a musician and poet. He is originally from Kentucky.
If you’re reading this, you probably don’t need to be persuaded that the planet is on fire, and we need to do something to put it out fast. We see evidence all around us: California is again in the throes of a record wildfire season, glaciers the size of Manhattan are sliding into the sea, and in some of the most densely populated parts of the world, massive cities are being swallowed by the tide. There is little dispute that these disasters stem from our burning of fossil fuels, and that by most any measure, we are failing to prevent the worst.
To put it politely, we of Divest Princeton say these partnerships do more harm than good. True, they may create new and valuable knowledge, but that isn’t really why they exist. In one leaked exchange from 1998, Exxon representatives strategized about the need to “identify and establish cooperative relationships with all major scientists whose research in the field supports our position,” and to “monitor and serve as an early warning system for scientific development with the potential to impact on the climate science debate, pro and con.”
Taking this statement literally — and why shouldn’t we? — BP and Exxon’s support for Princeton is more than simple altruism. It’s more than good PR. Rather, it’s part of a years-long effort not to aid, but to manage climate research toward ends not in conflict with their extractive business model. Tellingly, these do-gooder oil companies plan to increase production 35% by 2030. This would be cataclysmic.
Their schemes are made possible by funding and power gifted by Princeton. We cannot tolerate, let alone enable these activities any longer. Not when they pose such obvious conflicts with our university’s core values and threaten our fellow students and faculty working around the world. Princeton must stand up for itself. How better than by divesting from fossil fuels?
The divestment movement has grown rapidly in recent years, with institutions like Georgetown University, Brown, Cornell, and Oxford recently joining its ranks. Collective actions have taken a toll — Goldman Sachs says that divestment is partly to blame for widespread credit de-ratings in the coal industry, and Shell is on-record saying divestment will present “a material adverse effect on the price of our securities and our ability to access equity capital markets.” Essentially, divestment works.
We argue that the moral imperative of divestment should be compelling enough on its own; if Princeton moved to divest and the markets didn’t budge an inch, at least then our conscience would be clean. At least then we could call ourselves “sustainable” with a straight face and live honestly by our motto: “in the nation’s service, and the service of humanity.”
Detractors maintain that any “demands” on Princeton’s endowment would constrain its ability to earn huge returns, depriving students of the financial support they need to prosper. This is absurd. Billion-dollar endowments like the Rockefeller Brothers Fund have demonstrated that divestment can be a net positive. Fossil fuel stocks have also been declining for years. It looks increasingly clear that an investor gains little “diversifying” in fossil fuel, and that the risks of divestment have been well overblown. Shareholders — especially shareholders with a fiduciary responsibility like Princeton’s — should be looking for the exit.
In order to remain within 1.5°C of global warming by mid-century — the threshold at which the IPCC and Princeton’s own Sustainability Action Plan say “catastrophic consequences” will be unavoidable — the fossil fuel industry’s ambitious exploration and development will need to be mothballed. Undrilled oil fields and unmined coal will become stranded assets, or dead weight on their companies’ books. To have faith in these investments, Princeton must think stranded assets will actually go to use, in which case, Princeton ignores its own scientists and legitimizes the activities central to our climate crisis.
Others have argued that regardless of donors’ ulterior motives, divesting would only leave good money and research on the table. To these people, the “greenwashing” corporations seek from partnering with elite institutions is both inevitable and of little consequence compared to the novel scholarship their funding provides. The catch here is that quality research and a morally invested endowment are not mutually exclusive. There isn’t a rule saying our research must be funded by BP or Exxon — if Princeton truly valued this knowledge, it would channel its creative energies toward finding funding elsewhere.
“Elsewhere” could very easily be the university’s own wallet. Princeton is quick to remind us it holds the biggest per-student endowment in the country. The endowment today is a bit larger than $26 billion, roughly the size of Iceland’s GDP and larger than GDPs of half the world’s countries. In the lastten years alone, Princeton’s endowment has more than doubled. In this light, the money needed to sustain current research is practically a rounding error. If just a few Trusteesput their donations together, they could recoup Exxon’s latest $5 million donation in under five seconds!
We tried to anticipate these doubts in our divestment proposal, which was given to Princeton’s administration last February. Since then, we have met with Princeton’s Resources Committee and invited experts — former Committee Member Shannon Osaka, President of the Rockefeller Brothers Fund Stephen Heintz, and Stanford researcher Dr. Ben Franta — to help present our case. Discussions will continue through the end of 2020, culminating in a forum with 350.org’s Bill McKibben in November.
As a reward for our persistence, the Resources Committee has indicated it might decide on our proposal by Christmas. If it approves, the proposal goes to the Board of Trustees, and the clock starts over. This, dear readers, is the “fast track.”
It has been demoralizing to watch Princeton, one of the world’s great centers of higher learning and a temple to empirical evidence, run interference for companies that have scorned the truth, knowingly endangered billions, and literally confessed to their ill intent. From its byzantine system for proposing divestments to its arbitrary requirement saying divestment must take the form of complete dissociation (a prohibitively high bar), Princeton’s strategy is to frustrate and outlast causes like ours. Most of the time, it succeeds.
But our cause is different from the others. With climate change, waiting is simply not an option. The immovable object will meet an unstoppable force, and the unstoppable force will win.
The longer we delay, the longer we allow fossil fuel companies to weaponize Princeton’s gravitas, spreading disinformation and quack science while purporting to be part of “the solution.” Until Princeton inevitably divests from these bad actors, we will continue to withhold our donations, continue to protest, and continue to organize, fighting fire with fire.
Divest Princeton is a volunteer movement of Princeton students, alumni, parents, faculty, and staff. Sign their “No Donations Until Divestment” petition and learn more here.
Might there be a remedy for the worldwide temperature and rainfall changes caused by humanity’s emissions? If so, what would the cure cost? We watch as Mr. Human grapples with these questions with the help of Dr. Planet.
Dr. Planet was about to put an end to a long, hard day of work when the distress call came in.
“Dr. Planet! Dr. Planet! Our planet Earth needs your help!”
Dr. Planet quickly boarded his medical spaceship and sped towards the solar system. As the ship passed through Earth’s atmosphere, his instruments began to gather the planet’s climate records. The temperature indicator began to blink red. Then the indicator for circulation changes in its atmosphere and oceans. Then the sea ice indicator.
The moment Mr. Human boarded his spaceship, Dr. Planet knew why the planet was ill.
Mr. Human was holding a long, black cigar labelled ‘Fossil Fuels’. It was still smoking at the tip. In front of him, the reading on his carbon dioxide indicator soared.
“We know that,” said Mr. Human. He sounded as if he had not slept for days. “We’ve known about it for decades. I was so excited after the Paris meeting, when the world first agreed on concrete pledges to cut down emissions. Then we did our sums and realized that even if every country fulfilled its promised reductions, global mean temperatures were still set to increase by more than 2 degrees Celsius come 2100. And then the United States announced that they would pull out of the agreement, which was…”
Mr. Human’s gaze fell as he trailed off. He then straightened and looked Dr. Planet in the eye. “Dr. Planet, you are a renowned planetary climate surgeon. Do you have a geoengineering treatment that might be able to cure our Earth?”
Mr. Human took out a few geoengineering brochures and laid them on Dr. Planet’s desk. They had been produced by the hospital’s marketing department.
Dr. Planet resolved to have a chat with the marketing department about a more moderate portrayal. He was getting tired of patients either believing that geoengineering was a panacea or cursing him for attempting to play God. In fact, the carbon dioxide removal and solar geoengineering tools he possessed only allowed for a limited range of outcomes. More importantly, all of the choices involved tradeoffs and risks. However, experience had taught him that it was best to begin by explaining the science.
Carbon dioxide removal
Dr. Planet picked up the first brochure. It was about Canadian entrepreneur Russ George, who in 2012 dumped a hundred tons of iron into the ocean to trigger a massive plankton bloom. There were record hauls of salmon right after the fertilization. George also pointed out that the plankton removed carbon dioxide from the air as they grew.
“It’s easy to remove carbon dioxide from the atmosphere,” began Dr. Planet. “The problem is keeping the carbon dioxide out. If the fish is harvested and used as food, the carbon makes its way back into the air. Also, when the plankton respire, or are eaten by organisms higher up the food chain, most of that carbon is released once again. In addition, the immediate phytoplankton growth triggered by fertilization robs the iron or phosphorous that might have been used by other organisms. If you are looking for a long-term solution, don’t get tricked into looking only at the initial gains.”
“Besides, iron fertilization can’t be the only solution. In the most optimistic scenarios, the bulk of the carbon uptake would be used to form the shells of marine organisms such as diatoms. Since the shells would eventually fall to the bottom of the ocean, there would be a net removal of carbon from the surface. But based on the availability of iron-deficient waters around your planet, I estimate that iron fertilization can sequester at most 10% of human annual emissions.”
Mr. Human brightened as he saw that this technology could store about 1,600 billion tonnes of carbon dioxide. If humanity continued emitting at 2014 levels, this would lock up about 45 years of carbon dioxide emissions. When he came to the section on costs, his jaw dropped. “Double the cost of our existing power plants?” He took out his bulging wallet and removed a stack of bills. Dr. Planet wondered if Mr. Human considered this so cheap that he was willing to pay upfront.
Mr. Human waved the bills. “Look at all the IOUs! There is no way we can afford that cost. I’ll bet the aerosol plan is cheaper than that.”
Solar radiation management
Mr. Human pointed to a printout explaining how particles called aerosols could be placed high in the atmosphere. Choosing aerosols that reflected solar radiation would help cool the Earth’s surface.
Dr. Planet understood why Mr. Human liked the aerosol plan. It made sense to place the aerosols far above the surface. That way, it would take many months before the aerosols settled below the clouds, where rain could flush the particles from the air. Furthermore, after the eruption of Mount Pinatubo in 1991, global-mean temperatures in the Northern hemisphere fell by half a degree Celsius. With such a natural analog in mind, it was no wonder that Mr. Human thought he knew what to expect. He even was correct on the costs. Starting from 2040, dedicating 6700 flights a day to sulfate injection would keep global-mean warming to 2 degrees Celsius. This would involve a mass of sulfates roughly similar to that of the Pinatubo eruption and would cost about $US20 billion per year.
“It would be cheaper,” agreed Dr. Planet. “But tell me, is global mean surface temperature all you care about?”
“Of course not,” said Mr. Human. “Rainfall is important too. Also, I want to make sure we keep the West Antarctic Ice Sheet, and reduce…”
“Then I should let you know that using aerosols means making a choice between overcorrecting for temperature or precipitation,” said Dr. Planet. He used the same serious tone a human doctor might use to explain that chemotherapy might remove the tumor, but would also cause you to vomit and lose all your hair.
Mr. Human folded his arms. He looked most unconvinced.
As Dr. Planet cast about for a good explanation, his eyes fell on Mr. Human’s wallet. It was still on the table and still full of the IOUs. He picked up a stack of name cards from his table.
“What if I asked you to place all of the cards into your wallet?”
Mr. Human frowned at the thick wad of paper. “I would have to remove some of my old receipts, or the wallet wouldn’t close.”
“Think of the Earth’s surface as the full wallet,” Dr. Planet said. “If we put in energy from increasing sunlight, your Earth has to throw out some energy. Because we’re trying to keep the temperature unchanged, the surface can’t radiate more longwave radiation by warming. It therefore has to transport heat, which mostly happens through evaporation. In the atmosphere, what comes up must come back down eventually, so increasing evaporation increases rainfall.”
“So, increasing radiation towards the surface increases rainfall,” said Mr. Human. “Don’t sunlight and carbon dioxide both do that?”
“They do,” said Dr. Planet. “But the atmosphere is mostly transparent to solar radiation and mostly opaque to longwave radiation from carbon dioxide. Energy entering via solar radiation thus has a stronger impact on the surface and rainfall. Hence, trying to correct for the change in temperature from carbon dioxide by stratospheric aerosols is expected to lead to an overcorrection in precipitation .”
Mr. Human was silent for a while, before he perked up. “Well, a slight change in the weather we’re used to isn’t that bad, especially if it avoids a worse outcome. Besides, you’ve only talked about the global-mean. With some fine-tuning, I’m sure we could come up with an aerosol distribution that delivers a good balance.”
“However, given the lack of rigorous clinical trials on planets like your Earth, I must warn you that it will remain a highly uncertain procedure,” said Dr. Planet. “For one, we will encounter diminishing marginal returns as we attempt to increase the sulfate load to achieve cooling. The increased amount of sulfate in the atmosphere could form bigger particles that reflect sunlight less efficiently rather than create new ones.”
“The treatment procedure of sustaining the thousands of aerosol-injection flights will require the commitment and coordination of all the peoples of your planet. A disruption due to conflicts could be catastrophic. If the aerosol concentrations are not maintained, the decades’ worth of change from greenhouse gases that they are holding back would manifest in a couple of years. The change would be so sudden that there would be little time for you to adapt.”
Mr. Human paled. Countries might well balk at paying the geoengineering bill. After all, that was money that could go to feeding the poor or to reducing a budget deficit. A rogue country might threaten to disrupt the injections unless sanctions were lifted. Or a country that might benefit from warming could sabotage the flights…
“I think you already know what I’m about to say,” said Dr. Planet as Mr. Human buried his face in his hands. “There’s no magic pill here. There never has been. I can help perform some stopgap surgery by removing carbon dioxide or provide some symptomatic relief through solar radiation management. Ultimately, though, your species has to stop lighting up in the way it has.”
Mr. Human sighed; he had to deliver the sobering news that geoengineering was riskier and more complicated than his colleagues they had expected. As he rose from his chair, he realized that he was still holding his smoking carbon cigarette. The numbers on Dr. Planet’s carbon dioxide detector were still rising. He watched the readout as it went past 400ppm, then 410ppm. With a regretful sigh, he ground the lit end of his cigar into an ashtray and stepped out to continue the long journey ahead.
Acknowledgments: This article was inspired by a group discussion with Dr. Simone Tilmes at the 2017 Princeton Atmospheric and Oceanic Sciences Workshop on Climate Engineering. Katja Luxem and Ben Zhang read an early draft and helped improve the clarity of the article.
Xin is a PhD candidate in Princeton’s Program in Atmospheric and Oceanic Sciences, a collaboration between the Department of Geosciences and the NOAA Geophysical Fluid Dynamics Laboratory. She combines high-resolution models and theory to better understand the changes in tropical rainfall extremes as the atmosphere warms. She is also interested in innovative approaches to science communication.
The world faces an urgent need to drastically reduce climate-warming CO2 emissions. At the same time, however, reliance on the fossil fuels that produce CO2 emissions appears inevitable for the foreseeable future. One existing technology enables fossil fuel use without emissions: Carbon Capture and Sequestration (CCS). Instead of allowing CO2 emissions to freely enter the atmosphere, CCS captures emissions at the source and disposes of them at a long-term storage site. CCS is what makes “clean coal” – the only low-carbon technology promoted in President Donald Trump’s new Energy Plan – possible. The debate around the role of CCS in our energy future often includes questions such as: why do we need CCS? Can’t we simply replace fossil fuels with renewables? Where can we store CO2? Is storage safe? Is the technology affordable and available?
Fossil fuels are abundant, cheap, and flexible. They currently fuel around 80% of the global energy supply and create 65% of greenhouse gas emissions. While renewable energy production from wind and solar has grown rapidly in recent years, these sources still account for less than 2.1% of global energy supply. Wind and solar also face challenges in replacing fossil fuels, such as cost and intermittency, and cannot replace all fossil fuel-dependent processes. The other major low-carbon energy sources, nuclear and hydropower, face physical, economic, and political constraints that make major expansion unlikely. Thus, we find ourselves in a dilemma: fossil fuels will likely remain integral to our energy supply for the foreseeable future.
CO2 storage and its role in the energy transition
CCS captures CO2 emissions from industrial sources (e.g. electric power plants) and transports them, usually by pipeline, to long-term storage sites. The ideal places for CO2 sequestration are porous rock formations more than half a mile below the surface. (Target rocks are filled with water, but don’t worry, it’s saltwater, not freshwater!) Chosen formations are overlain, or “capped,” by impermeable caprocks that do not allow fluid to flow through them. The caprocks effectively trap buoyant CO2 in the target rocks (see Figure 2).
Scientists estimate that suitable rock formations have the potential to store more than 1,600 billion tonnes of CO2. This amounts to 70 years of storage for current global emissions from capturable sources (which are 50% of all emissions). Large-scale CCS could serve as a “bridge,” buying time for carbon-free energy technologies to develop to the stage where they are economically and technically ready to replace fossil fuels. CCS could even help us increase the amount of intermittent renewable energy by providing a flexible and secure “back-up” with low emissions. Bioenergy combined with CCS (BECCS) can also deliver “negative emissions” that may be needed to stabilize the climate. Furthermore, industrial processes such as steel, cement, and fertilizer production have significant CO2 emissions and few options besides CCS to reduce them.
While our summary makes CCS seem like an obvious technology to implement, important questions about safety, affordability, and availability remain.
Is CCS Safe?
For CCS to contribute substantially to global emissions reduction, huge amounts of emissions must be stored underground for hundreds to thousands of years. That’s a long time, which means the storage must be very secure. Some worry that CO2 might leak upward through caprock formations and infiltrate aquifers or escape to the atmosphere.
But evidence shows that CO2 can be safely and securely stored underground. For example, the Sleipner project has injected almost 1 million tonnes of CO2 per year under the North Sea for the past 20 years. (For scale, that’s roughly a quarter of the emissions from a large coal power plant.) The oil industry injects even larger amounts of CO2 – approximately 20 million tonnes per year – into various geological formations in the United States without issue in enhanced oil recovery operations to increase oil production. Indeed, the oil and gas deposits we currently exploit demonstrate how buoyant fluids (like CO2) can be securely stored in the subsurface for a very long time.
Still, there are risks and uncertainties. Trial CO2 injections operate at much lower rates than will be needed to meet our climate targets. Higher injection rates require pressure management to prevent the caprock from fracturing and, consequently, the CO2 from leaking. The CO2 injection wells and any nearby oil and gas wells also present possible leakage pathways from the subsurface to the atmosphere (although studies suggest this is likely to be negligible). Leading practices in design and maintenance can minimize well leakage risks.
Subsurface CO2 storage has risks, but experience suggests the risks can be mitigated. So, if CCS has such promise for addressing our climate-energy problem, why has it not been widely implemented?
The current state of CCS
CCS development has lagged, and deployment remains far from the scale required to meet our climate targets. Only a handful of projects have been built over the past decade. Why? High costs and a lack of economic incentives.
Adding CCS to coal and gas-fired electricity generation plants has large costs (approximately doubling the upfront cost of a new plant using current technology). Greenhouse gases are free (or cheap) to emit in most of the world, which means emitters have no reason to make large investments to capture and store their emissions. In order to incentivize industry to invest in CCS, we would need to implement a strong carbon price, which is politically unpopular in many countries. (There are exceptions – Norway’s carbon tax incentivized the Sleipner project.) In the United States, the main existing economic incentive for capturing CO2 is for enhanced oil recovery operations. However, the demand for CO2 from these operations is relatively small, geographically localized, and fluctuates with the oil price.
Inconsistent and insufficient government policies have thwarted significant development of CCS (the prime example being the UK government’s last-minute cancellation of CCS funding). Another challenge will be ownership and liability of injected CO2. Storage must be guaranteed for long timeframes. Government regulations clarifying liability, long-term responsibility for stored CO2, and monitoring and verification measures will be required to satisfy investors.
The future of CCS
The ambitious target of the Paris Agreement will require huge cuts in CO2 emissions in the coming decades. The targets are achievable, but probably not without CCS. Thus, incentives must increase, and costs must decrease, for CCS to be employed on a large scale.
Despite its current troubles, CCS is an important part of solving our energy and climate problem. The recent United States election has created much uncertainty about future climate policy, but CCS is one technology that could gain support from the new administration. In July 2016, a bipartisan group of senators introduced a bill to support CCS development. If passed, this bill would satisfy Republican goals to support the future of fossil fuel industries while helping the United States achieve its climate goals. Strong and stable supporting policies must be enacted by Congress – and governments around the world – to help CCS play its key role in the climate fight.
Kasparas Spokas is a Ph.D. candidate in the Civil & Environmental Engineering Department at Princeton University studying carbon storage and enhanced oil recovery environments. More broadly, he is interested in studying the challenges of developing low-carbon energy systems from a techno-economic perspective. Follow him on Twitter @KSpokas
Ryan Edwards is a 5th year PhD candidate in Princeton’s Department of Civil & Environmental Engineering. His research focuses on questions related to geological carbon storage, hydraulic fracturing, and shale gas. He is interested in finding technical and policy solutions to the energy-climate problem. Follow him on Twitter @ryanwjedwards.
On the subject of climate change, one of the most widely cited numbers is that humans have increased the net radiation balance of the Earth’s lower atmosphere by approximately 2.3 W m-2 (Watts per square meter) since pre-industrial times, as determined by the Intergovernmental Panel on Climate Change (IPCC) in their most recent Fifth Assessment Report (AR5). This change is termed radiative forcing and represents a basic physical driver of higher average surface temperatures resulting from human activities. In short, it elegantly captures the intensity of climate change in a single number – the higher the radiative forcing, the larger the human influence on climate and the higher the rate of increasing surface temperatures. Radiative forcing is also significant because it forms the basis of equivalence metrics used in international environmental treaties, defines the endpoint of the future scenarios commonly used for climate change simulations, and is physically simple enough that it should be possible to calculate without relying on global climate models.
Given its widespread use, it is important to understand where estimates of radiative forcing come from. Answering this question is not straightforward because AR5 is a lengthy report published in three separate volumes. Chapter 8 of Volume 1, more than any other, quantitatively describes why climate change is occurring due to natural and anthropogenic causes and is, therefore, the primary source for how radiative forcing is assessed by the IPCC. One of the key figures is reproduced below, illustrating that the basic drivers of climate change are human-driven changes to aerosols (particles suspended in the air) and greenhouse gases, along with their relative strengths and uncertainties:
This post seeks to answer two questions: how is the 2.3 W m-2 best estimate determined in AR5? And further, why is total anthropogenic forcing not known more precisely than shown in Figure 1 given the numerous observations currently available?
1. Variations on the meaning of radiative forcing
Fundamental laws of physics say that if the Earth is in equilibrium, then average temperature of the Earth is such that there is a balance between the energy that the Earth receives and the energy that it radiates. When this balance is disturbed, the climate will respond due to the additional energy in the system and will continue to change until the forcing has fully propagated through the climate system at which point a new equilibrium (average temperature) is reached. This response is controlled by processes with a range of timescales (e.g. the surface ocean over several years and glaciers over many hundreds of years), so radiative forcing depends on when exactly it is calculated. This leads to several subtly differing definitions. While the IPCC distinguishes between radiative forcing and effective radiative forcing, I do not attempt to distinguish between the two definitions here and refer to both as radiative forcing.
Figure 2 shows the general framework for assessing human drive change used by the IPCC, which is divided into four major components. Firstly, the direct impact of human activities through the release (emission) of greenhouse gases and particulates into the atmosphere is estimated, along with changes to the land surface through construction and agriculture. These changes cause the accumulation of long-lived gases in the atmosphere including carbon dioxide, the indirect formation of gases through chemical reactions, and an increase in number of aerosols in the atmosphere (abundance). Each of these agents influences the radiation balance of the Earth (forcing) and over time causes warming near the surface (climate response).
2. Individual drivers of change
The two major agents (aerosols and greenhouse gases) are further sub-divided by the IPCC as shown below. Each of the components are assessed independently, then summed together using various statistical techniques to produce the best estimate and range shown in Figure 1.
Since the report itself is an assessment, each of the estimates in Figure 3 were derived directly from the peer-reviewed literature and are not the result of new model runs or observations. I have recently identified the specific sources incorporated in this figure elsewhere if one wants to know exactly how any of the individual bars were calculated. More generally, it can be seen that the level of confidence varies for each agent, with the most uncertainty for aerosol-radiation and aerosol-cloud interactions. Positive warming is driven most strongly by carbon dioxide followed by other greenhouse gases and ozone. It can also be seen that changes in solar intensity are accounted for by the IPCC, but are believed to be small compared to changes from the human-driven processes.
3. Can net radiative forcing be more directly calculated?
Besides adding together individual processes, is it also possible to independently assess the total forcing itself, at least over recent decades where satellite and widespread ground-based observations are available? In principle, changes in the Earth’s energy balance, primarily seen as reduced thermal radiation escaping to space and as heat uptake by the oceans, should relate back to the net forcing causing these changes in a way that provides an alternate means of calculating human’s influence on the climate. To use this approach, one would need a good idea of how sensitive the Earth’s response will be in response to a given level of forcing. However, this sensitivity is equally or more uncertain than the forcing itself, making it difficult to improve on the process-by-process result. The ability to account for the Earth’s overall energy balance and then quantify radiative imbalances over time also remains a challenge. Longer data records and improved knowledge of climate sensitivity may eventually advance the ability to directly determine total radiative forcing going forward.
The most widely cited number is based on an abundance-based perspective with step changes for each forcing agent from 1750 to 2011, resulting in an estimated total forcing of 2.3 W m-2. This number does not come from an average of global climate models, as might be imagined, but instead is the sum of eight independent components (seven human-driven, one natural), each derived and assessed from selected recent sources in the peer-reviewed literature.
Radiative forcing is complex and requires models to translate how abundances of greenhouse gases and aerosols actually affect global climate. For gases like carbon dioxide, documented records are available going back to pre-industrial times and earlier, but in other cases additional modelling is needed to help determine the natural state of the land surface and atmosphere. The total human-driven radiative forcing (Figure 1) is still surprisingly poorly constrained in AR5 (1.1 to 3.3 W m-2 with 90% confidence), which is a reminder that while we are certain human activities are causing more energy to be retained by the atmosphere, continued work is needed on the physical science of climate change to determine by exactly how much.
Levi Golston is a PhD candidate in Princeton’s Environmental Engineering and Water Resources program. His research develops laser-based sensors coupled with new atmospheric measurement techniques for measuring localized sources, particularly for methane and reactive nitrogen from livestock, along with methane and ethane from natural gas systems. He blogs at lgsci.wordpress.com/
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.
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.
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.
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.
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.
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.
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.
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).
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.
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.
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.
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).
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?
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.
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.