level rise is one of the most challenging impacts of climate change. The
continued rise in sea levels, partially caused by the melting of the ice sheets
of Greenland and Antarctica, will result in large scale impacts in coastal
areas as they are submerged by the sea. Locations not able to bear the costs of
implementing protection and adaptation measures will have to be abandoned,
resulting in social, economic and environmental losses.
most important mitigation goal for sea level rise is to reduce or possibly
revert carbon dioxide (CO2) emissions. Given the time lag between
emission reductions and the impacts of climate change, new adaptation measures
to reduce sea level rise should be proposed, developed and if possible,
A proposal that I developed during my D.Phil degree ten years ago, which resulted in a paper on the Mitigation and Adaptation to Global Change Journal1, shows that submerged barriers in front of ice sheets and glaciers would contribute to reducing the ice melt in Greenland. Edward Byers and I propose the construction of ten barriers at key glaciers in Greenland to stop the flow of warm salty ocean water reaching glaciers in Greenland and Atlantic, which are the main contributors to ice melting. This could reduce sea level rise by up to 5.3 meters at a levelized cost of US$275 million a year. The cost of the barriers is only a fraction of the estimated costs of adaptation measures to sea level rise around the world estimated to be US$1.4 trillion a year by 21002.
barrier consists of several plain sheet modules of marine grade steel around
200 mm thick connected to cylindrical steel tubes with air inside to keep the
barrier floating. The depth of the barriers varies from 30 – 500 meters and the
required length to stop the sea water from entering the fjords, where the
glaciers are located. As no such barrier has been developed before,
we propose three main
steps for the construction of the barrier:
The barrier components
should be transported to the designated location during the summer, when there
is no ocean ice cover and the access to the location of the barrier is less
challenging. Also during the summer, mooring structures should be added.
During the winter, the
barrier is assembled over the frozen ice cover.
During the next summer,
the ice cover will melt again and the barrier will float above the place where
it is should be fixed. The mooring chains attached to the barrier will pull the
barrier into place, using the mooring structures in the ground.
The concept of reducing the contact of seawater and glaciers to reduce ice sheet melting was first published by Moore in Nature3, and Wolovick in The Cryosphere4 with the construction of submerged dams. A graphic representation of the concept is presented in Figure 1. As you can see the barriers should be positioned just after the glacier cavity, where the depth required for the barrier would be the smallest. Our cost analysis shows that using submerged barriers would have one or two orders of magnitude lower costs when compared to submerged dams. Additionally, submerged barriers could be easily removed, if the need arise.
are several issues involving the implementation of these barriers that should
be considered before they are built. The reduction of ice melt in Greenland
glaciers will contribute to an increase in seawater temperature and salinity of
the Arctic Ocean, which will have a direct impact on the region’s biosphere,
climate and ocean currents. The superficial ice cover in the Arctic will be
considerably reduced. This would allow a new maritime route for ships to cross
the Arctic Ocean, increase the absorption of CO2 by the Arctic Ocean,
due to the increase in the ice free surface area and the cold seawater temperature,
and the increase in radiation heat from the Arctic Ocean into space. Ice is a
strong thermal insulator. Without the Arctic Ocean ice cover the temperature of
the region and the heat radiated from the Earth to space will considerably
increase, which could have a higher impact in cooling the Earth than the ice
cover’s albedo effect. Thus, the reduction of the Arctic Ocean ice cover could
contribute to reducing the overall CO2 concentration of the
atmosphere and reducing the Earth’s temperature.
solution, however, should not be used as an excuse to reduce focus on cutting
CO2 emission. If the world continues to warm, not even submerged
barriers in front of glaciers would be able to stop ice sheets melting and sea
Hunt J, Byers E (2018) Reducing sea level rise with submerged barriers and dams in Greenland. Mitigation and Adaptation Strategies for Global Change DOI: 10.1007/s11027-018-9831-y. [pure.iiasa.ac.at/15649]
Jevrejeva JS, Jackson LP, Grinsted A, Lincke D, and Marzeion B (2018) Flood damage costs under the sea level rise with warming of 1.5 ◦C and 2 ◦C. Environmental Research Letters DOI: 10.1088/1748-9326/aacc76
Moore J, Gladstone R, Zwinger T, and Wolovick M (2018) Geoengineer polar glaciers to slow sea-level rise. Nature: /
Wolovick M, Moore J (2018) Stopping the flood: could we use targeted geoengineering to mitigate sea level rise? The Cryosphere DOI: 10.5194/tc-12-2955-2018
By Marcus Thomson, researcher, IIASA Ecosystems Services and Management Program
While living in Cairo in 2010, I witnessed first-hand the human toll of political and environmental disasters that washed over Africa at the end of the last century. Unprecedented numbers of migrants were pressing into North Africa, many pushed out of their homelands by conflict and state-failure, pulled towards safer, richer, less fragile places like Europe. Throughout Sub-Saharan Africa, climate change was driving up competition for scarce land and water, and raising pressure on farmers to maintain the quantity and quality of their crops.
It is a similar story throughout the developing world, where many farmers do without the use of expensive chemical fertilizer and pesticides, complex irrigation, or boutique seed varieties. They rely instead on traditional land management practices that developed over long periods with consistent, predictable conditions. It is difficult to predict how dryland farmers will respond to climate change; so it is challenging to plan for various social, economic, and political problems expected to develop under, or be exacerbated by, climate change. Will it spur innovation or, as has been argued for the Syrian civil war, set up conflict? A major stumbling block is that the dynamics of human social behavior are so difficult to model.
Instead of attempting to predict farmers’ responses to climate change by modelling human behavior, we can look to the responses to environmental changes of farmers from the past as analogues for many subsistence farmers of the future. Methods to fill in historical gaps, and reconstruct the prehistoric record, are valuable because they expand the set of observed cases of societal-scale responses to environmental change. For instance, some 2000 years ago, an expansive maize-growing cultural complex, the Ancestral Puebloans (APs), was well established in the arid American Southwest. By AD 1000, members of this AP complex produced unique and innovative material culture including the famed “Great Houses”, the largest built structures in the United States until the 19th century. However, between AD 1150 and 1350, there was a profound demographic transformation throughout the Southwest linked to climate change. We now know that many APs migrated elsewhere. As a PhD student at the University of California, Los Angeles, I wondered whether a shift to cooler, more variable conditions of the “Little Ice Age” (LIA, roughly AD 1300 to 1850) was linked to the production of their staple crop, maize.
I came to IIASA as a YSSP in 2016 to collaborate with crop modelers on this question, and our work has just been published in the journal Quaternary International. I brought with me high-resolution data from a state-of-the-art climate model to drive the crop simulations, and AP site information collected by archaeologists. Because AP maize was quite different from modern corn, I worked with IIASA soil scientist Juraj Balkovič to modify the crop simulator with parameters derived from heirloom varieties still grown by indigenous peoples in the Southwest. I and IIASA economic geographer Tamás Krisztin developed a statistical technique to analyze the dynamical relationship between AP site occupation and simulated yield outcomes.
We found that for the most climate-stressed high-elevation sites, abandonments were most associated with increased year-to-year yield variability; and for the least stressed low-elevation and well-watered sites, abandonment was more likely due to endogenous stressors, such as soil degradation and population pressure. Crucially, we found that across all regions, populations peaked during periods of the most stable year-to-year crop yields, even though these were also relatively warm and dry periods. In short, we found that AP maize farmers adapted well to gradually rising temperatures and drought, during the MCA, but failed to adapt to increased climate variability after ~AD 1150, during the LIA. Because increased variability is one of the near certainties for dryland farming zones under global warming, the AP experience offers a cautionary example of the limits of low-technology adaptation to climate change, a business-as-usual direction for many sub-Saharan dryland farmers.
This is a lesson from the past that policymakers might take note of.
 Kelley, C. P., Mohtadi, S., Cane, M. A., Seager, R., & Kushnir, Y. (2015). Climate change in the Fertile Crescent and implications of the recent Syrian drought. Proceedings of the National Academy of Sciences, 201421533.
 Thomson, M. J., Balkovič, J., Krisztin, T., MacDonald, G. M. (2018). Simulated crop yield for Zea mays for Fremont Ancestral Puebloan sites in Utah between 850-1499 CE based on temperature dailies from a statistically downscaled climate model. Quaternary International. https://doi.org/10.1016/j.quaint.2018.09.031
On 14 and 15 May, Vienna hosted two important events within the frame of the world energy and climate change agendas: the Vienna Energy Forum and the R20 Austrian World Summit. Since I had the pleasure and privilege to attend both, I would like to share some insights and relevant messages I took home with me.
To begin with, ‘renewable energy’ was the buzzword of the moment. Renewable energy is not only the future, it is the present. Recently, 20-year solar PV contracts were signed for US$0.02/kWh. However, renewable energy is not only about mitigating the effects of climate change, but also about turning the planet into a world we (humans from all regions, regardless of the local conditions) want to live in. It is not only about producing energy, about reaching a number of KWh equivalent to the expected demand–renewables are about providing a service to communities, meeting their needs, and improving their ways of life. It does not consist only of taking a solar LED lamp to a remote rural house in India or Africa. It is about first understanding the problem and then seeking the right solution. Such a light will be of no use if a mother has to spend the whole day walking 10 km to find water at the closest spring or well, and come back by sunset to work on her loom, only to find that the lamp has run out of battery. Why? Because her son had to take it to school to light his way back home.
This is where the concept of ‘nexus’ entered the room, and I have to say that more than once it was brought up by IIASA Deputy Director General Nebojsa Nakicenovic. A nexus approach means adopting an integrated approach and understanding both the problems and the solutions, the cross and rebound effects, and the synergies; and it is on the latter that we should focus our efforts to maximize the effect with minimal effort. Looking at the nexus involves addressing the interdependencies between the water, energy, and food sectors, but also expanding the reach to other critical dimensions such as health, poverty, education, and gender. Overall, this means pursuing the Sustainable Development Goals (SDGs).
Another key word that was repeatedly mentioned was finance. The question was how to raise and mobilize funds for the implementation of the required solutions and initiatives. The answer: blended funding and private funding mobilization. This means combining different funding sources, including crowd funding and citizen-social funding initiatives, and engaging the private sector by reducing the risk for investors. A wonderful example was presented by the city of Vienna, where a solar power plant was completely funded (and thus owned) by Viennese citizens through the purchase of shares.
This connects with the last message: the importance of a bottom-up approach and the critical role of those at the local level. Speakers and panelists gave several examples of successful initiatives in Mali, India, Vienna, and California. Most of the debates focused on how to search for solutions and facilitate access to funding and implementation in the Global South. However, two things became clear. Firstly, massive political and investment efforts are required in emerging countries to set up the infrastructural and social environment (including capacity building) to achieve the SDGs. Secondly, the effort and cost of dismantling a well-rooted technological and infrastructural system once put in place, such as fossil fuel-based power networks in the case of developed countries, are also huge. Hence, the importance of emerging economies going directly for sustainable solutions, which will pay off in the future in all possible aspects. HRH Princess Abze Djigma from Burkina Faso emphasized that this is already happening in Africa. Progress is being made at a critical rate, triggered by local initiatives that will displace the age of huge, donor-funded, top-down projects, to give way to bottom-up, collaborative co-funding and co-development.
Overall, if I had to pick just one message among the information overload I faced over these two days, it would be the statement by a young fellow in the audience from African Champions: “Africa is not underdeveloped, it is waiting and watching not to repeat the mistakes made by the rest of the world.” We should keep this message in mind.
Here, we respond to three important themes raised in these comments. The first concerns the interpretation of our findings about the significance of subsidy removal for reducing CO2 emissions, the second concerns our approach to modeling and the data we used, and the third relates to policy options for more effective subsidy reform.
What are fossil fuel subsidies and why are they interesting for climate?
Fossil fuel subsidies are government interventions which decrease the price of fossil fuels below the market price. They can go to supporting the extraction of oil, gas, and coal (production subsidies) or making fuels cheaper for consumers (consumption subsidies) and amounted to over US$400 billion in 2015. There is a certain irony in that so many governments signed on to the Paris Agreement in 2015 yet in that same year many of those same governments spent so much money making fossil fuels cheaper.
How much would removing these subsidies help climate change mitigation efforts? How does it compare to what countries have already pledged to do for the climate under the Paris Agreement?
Comparing emission reductions from subsidy removal to key climate targets
Some commenters claim that it is already known that the effect of removing fossil fuel subsidies on emissions is limited. However, according to the authoritative Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5), subsidy reform “can achieve significant emission reductions”. This view also is evident in the political sphere as: the Friends of Fossil Fuel Subsidy Reform, a group of countries called fossil fuel subsidy reform “the missing piece of the puzzle in the fight against climate change”.
Our findings are that fossil fuel subsidy removal would lead to a 1-4% reduction in CO2 emissions in the energy sector by 2030 if oil prices stay low, and 1-5% if oil prices rise again, compared to the rise in emissions if subsidies are maintained, the baseline. It means that subsidy reform is a modest contribution to the global reductions required to achieve 2°C in a least-cost pathway, 27-57% by 2030.
More importantly, in our paper we compare emission reductions from subsidy removal not to this ideal goal, but to the actual targets pledged in the context of the Paris Agreement. Globally, Paris pledges would reduce emissions against the baseline in the energy sector by 9-13% in 2030 (under a moderate growth baseline) which is a larger reduction than fossil fuel subsidy removal would deliver. Under both the Paris climate pledges and fossil fuel subsidy phase-out global emissions would continue to rise whereas to achieve the 2°C target they should peak and eventually decline.
Identifying the regions with greatest impact
This global assessment is only part of our study. In addition, we show how the impacts of subsidy removal are different by region. In the major oil and gas exporting regions (Middle East and North Africa, Russia and its neighboring countries, and Latin America), removing fossil fuel subsidies lowers emissions by the same amount or more than these countries’ Paris pledges. Government revenues in these regions largely come from energy exports, which are squeezed by today’s low oil prices. Lowering government spending by removing subsidies is a real political opportunity to reduce emissions in these regions.
In other developing and emerging economies (India, China, the rest of Asia and Sub-Saharan Africa), removing fossil fuel subsidies has less of an effect on emissions than these countries’ Paris pledges. In addition, the number of people who might be affected by subsidy removal in these regions is higher, simply because there are many more people living below the poverty line, for whom subsidies make the most difference. Taken together, these two findings frame one of our main results: that subsidy removal would be most useful for the climate precisely in the regions where it would affect fewer people living below the poverty line.
Data on subsidies
The second theme we would like to address relates to our data and modeling. Some commenters claimed that we underestimate both production subsidies and the effect of their removal.
According to data from the IEA and OECD only about 4% of subsidies are production subsidies. The International Institute for Sustainable Development (IISD) and Overseas Development Institute (ODI) publish an independent estimate based on their own definition and approach. Extrapolating to the global level, production subsidies would be about 14% in 2013 under their approach. We ran a sensitivity analysis using this higher production subsidies estimate. This did not change our findings (discussed in the Supplementary Information to our article).
There are other, fragmented estimates for electricity generation subsidies in individual countries, which generally take a different view of subsidies. For example, the recent report from IISD on Chinese subsidies to coal-fired power plants indicates that in 2014 and 2015, between 89% and 97% of these subsidies went to incentivize air pollution control equipment or closing inefficient plants. According to the same report, these subsidies also dropped by half from 2014 to 2015. Few governments would consider this as an environmentally-harmful subsidy, and removing such support will increase, not decrease emissions.
For our main analysis, we relied on IEA and OECD data for both production and consumption subsidies because these inventories are aligned with governments’ own estimates which are prepared as part of the G20 pledge to remove subsidies from 2009 reaffirmed in 2016. By using the same input data as governments and international organizations who are pledging or considering fossil fuel subsidy removal, we ensure the policy relevance of our results for these actors.
Estimating the effects of production subsidy removal
There were several comparisons of our results with those reported in a recent paper by Erickson et.al. in Nature Energy, which found that under the currently low oil prices, removing production subsidies in the US would make several oil fields unprofitable and eventually result in their closure. We find contrasting these two papers misleading as they ask very different research questions. Our study does not investigate how many oil fields in the US or elsewhere will become unprofitable after subsidy removal, but looks at the global effect of subsidy removal on emissions by taking into account trade in fossil fuels, the demand response and potential substitution of fuels and technologies. Erickson and his colleagues do not ask how much emissions will change as a result of closed oil fields. These are two very different questions.
Erickson and his colleagues compare the amount of carbon embedded in the oil reserves that may become unprofitable due to subsidy removal, to how much carbon the US would be allowed to emit under a stringent climate target. This creates an impression that they investigate the impact of removing oil production subsidies on US emissions. However, calculating the emission impact from removing oil production subsidies requires not only calculating the emissions embedded in foregone oil production, but also the possible emissions resulting from replacing this lost oil with other fuels, or changes in demand, for example if Americans choose to drive less if wells are closed, or if the US imports oil instead. We use these types of feedbacks in our models to calculate the emissions effects of subsidy removal (both consumption and production).
Redirecting subsidy funds
The third theme raised in the comments to our article was why we did not model redirecting subsidies to supporting renewable energy. While this is a very tempting question to ask from a climate perspective, and certainly one which we could do in our models, we did not consider it a realistic policy to be prioritized in our scenarios. In most countries fuel subsidies were introduced to support those on low incomes, although it is an inefficient way to do so. A state budget deficit and today’s low oil prices can often prompt successful subsidy reform. Indonesia for example recently expanded spending on infrastructure and programs to reduce poverty, while India introduced vouchers for cooking fuels. Iran, meanwhile introduced universal health coverage.
We do however hope that our transparent and rigorous assessment of the effects of subsidy removal on CO2 emissions and energy use will support realistic and effective subsidy removal policies, and help in understanding the relative importance of a range of emission-reduction measures needed for achieving the ambitious long-term targets of the Paris Agreement.
As some commenters pointed out, we need all tools in the box to combat the enormous challenge of climate change. We fully agree. At the same time, we also believe in the need to understand how much each tool can do and where it can be most effective. This is exactly what our study answers.
Jewell J, McCollum, D Emmerling J, Bertram C, Gernaat DEHJ, Krey V, Paroussos L, Berger L, Fragkiadakis K, Keppo I, Saadi, N, Tavoni M, van Vuuren D, Vinichenko V, Riahi K (2018) Limited emission reductions from fuel subsidy removal except in energy exporting regions. Nature DOI: 10.1038/nature25467
Note: This article gives the views of the author, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.
Is there a conflict between reducing global income inequality and combating climate change? This seems like an odd question, given that these challenges have a lot in common. Raising the living standard of the poor for example, makes them resilient to climate impacts; less inequality can mean more political mobilization to establish climate policies; and changes in social norms away from material accumulation can reduce inequality and emissions. Academics have however been curious about the following phenomenon: In many countries, a dollar spent at higher income levels is less energy intensive than at lower income levels (known as “income elasticity of energy”). That is, rich people – although they consume much more in total – spend additional income on services or can afford energy-efficient goods, while the new middle class buy energy-intensive goods, like appliances and cars.
Many imagine China as a template for this type of fast growth. If globally significant, this effect would imply that growth that is more equitable would also be more emissions-intensive, and that we would have to pay particular attention to ensuring that climate policies reach the rising middle class in developing countries. While several studies have examined this phenomenon in specific countries, no one has examined its global significance. We set out to do that.
Energy intensity (MJ per $) lower in a high-growth, low inequality world (green line, Gini=0.29) compared to a low-growth, high inequality world (blue line, Gini=0.45). Gini reflects between-country inequality only.
Our analysis suggests that the energy-increasing effect of lowering inequality is more of a distraction than a concern. We compared scenarios of equitable and inequitable income growth, both within and between countries, assuming the most extreme manifestation of the income elasticity. Within any country, given the slow pace at which inequality typically evolves even with the most extreme known income elasticity and reduction in country inequality, greenhouse gas emissions would increase by less than 8% over a couple of decades. However, when one considers a more equitable distribution of growth between countries, global emissions growth may decrease when compared to growth that occurs in industrialized countries. This is because poorer countries have more potential for technological advancements that reduce the energy intensity of growth than richer countries do. That is, more income growth in poorer countries provides more opportunity for efficiency improvements that influence the emissions of very large populations. Furthermore, China is a poor model for poor countries at large, many of which have relatively low energy intensities, even today.
Climate stabilization at the level aspired to by the Paris Climate Agreement requires that we (i.e. the world) decarbonize to zero annual emissions around 2050, which means that even developing countries have to make aggressive strides towards integrating climate goals into development. Nevertheless, there is no sufficient basis for considering that equitable growth, and by implication the poor’s energy intensity, is part of the problem. To the contrary, the potential for co-benefits from equitable growth for climate change are enormous, but unfortunately under-explored, particularly in quantitative studies. Research should focus on quantifying the role of changing social norms – less consumerism, political mobilization, and other social changes that are typically associated with lower inequality – on reducing greenhouse gases.
Rao, ND, Min J. Less global inequality can improve climate outcomes. Wiley Interdisciplinary Reviews: Climate Change. 2018;e513. https://doi.org/10.1002/wcc.513
Note: This article gives the views of the author, and not the position of the Nexus blog, nor of the International Institute for Applied Systems Analysis.
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