Running global models in a castle in Europe

By Matt Cooper, PhD student at the Department of Geographical Sciences, University of Maryland, and 2018 winner of the IIASA Peccei Award

I never pictured myself working in Europe.  I have always been an eager traveler, and I spent many years living, working and doing fieldwork in Africa and Asia before starting my PhD.  I was interested in topics like international development, environmental conservation, public health, and smallholder agriculture. These interests led me to my MA research in Mali, working for an NGO in Nairobi, and to helping found a National Park in the Philippines.  But Europe seemed like a remote possibility.  That was at least until fall 2017, when I was looking for opportunities to get abroad and gain some research experience for the following summer.  I was worried that I wouldn’t find many opportunities, because my PhD research was different from what I had previously done.  Rather than interviewing farmers or measuring trees in the field myself, I was running global models using data from satellites and other projects.  Since most funding for PhD students is for fieldwork, I wasn’t sure what kind of opportunities I would find.  However, luckily, I heard about an interesting opportunity called the Young Scientists Summer Program (YSSP) at IIASA, and I decided to apply.

Participating in the YSSP turned out to be a great experience, both personally and professionally.  Vienna is a wonderful city to live in, and I quickly made friends with my fellow YSSPers.  Every weekend was filled with trips to the Alps or to nearby countries, and IIASA offers all sorts of activities during the week, from cultural festivals to triathlons.  I also received very helpful advice and research instruction from my supervisors at IIASA, who brought a wealth of experience to my research topic.  It felt very much as if I had found my kind of people among the international PhD students and academics at IIASA.  Freed from the distractions of teaching, I was also able to focus 100% on my research and I conducted the largest-ever analysis of drought and child malnutrition.

© Matt Cooper

Now, I am very grateful to have another summer at IIASA coming up, thanks to the Peccei Award. I will again focus on the impact climate shocks like drought have on child health.  however, I will build on last year’s research by looking at future scenarios of climate change and economic development.  Will greater prosperity offset the impacts of severe droughts and flooding on children in developing countries?  Or does climate change pose a hazard that will offset the global health gains of the past few decades?  These are the questions that I hope to answer during the coming summer, where my research will benefit from many of the future scenarios already developed at IIASA.

I can’t think of a better research institute to conduct this kind of systemic, global research than IIASA, and I can’t picture a more enjoyable place to live for a summer than Vienna.

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.

Rescuing the world from drowning

By Julian Hunt, IIASA postdoc

Possible location where the barriers could be installed © Anna Krivitskaia |

Sea 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.

The 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, implemented.

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.

The 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:

  1. 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.
  2. During the winter, the barrier is assembled over the frozen ice cover.
  3. 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.

Figure 1. (a) Proposed location of the submerged barrier or dam, (b) submerged barrier characterizes, (c) submerged dam characterizes.

There 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.

This 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 level rise.


  1. 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.   []
  2. 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
  3. Moore J, Gladstone R, Zwinger T, and Wolovick M (2018) Geoengineer polar glaciers to slow sea-level rise. Nature:
  4. 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

Insights into the future of agriculture from past human climate change responses

Ancestral Puebloans

© Marcus Thomson

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[1], 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.[2] 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.

[1] 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.

[2] 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.

Impressions and messages from the Vienna Energy Forum and the R20 Austrian World Summit 2018

By Beatriz Mayor, Research Scholar at IIASA

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.

Beatriz Mayor at the Austrian World Summit

Beatriz Mayor at the Austrian World Summit © Beatriz Mayor

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).

VEF2018 banner

Vienna Energy Forum banner created by artists on the day © UNIDO / Flickr

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.

Emission reductions from fuel subsidy removal – the researchers respond to the debate

By Jessica Jewell, David McCollum, Johannes Emmerling, Christoph Bertram, David E.H.J. Gernaat, Volker Krey, Leonidas Paroussos, Loïc Berger, Kostas Fragkiadakis, Ilkka Keppo, Nawfal Saadi, Massimo Tavoni, Detlef van Vuuren, Vadim Vinichenko, Keywan Riahi

Our recent paper about our research on the effects of removing fossil fuel subsidies, published in Nature on February 8, 2018, generated a lot of comment and debate.

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.

Nodding donkeys

© Shutterstock / huyangshu

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).

Some commenters claimed that our study does not consider electricity production subsidies. This is also not true. We use the IEA data where power generation subsidies are captured in electricity subsidies. The SI discusses how each model integrates electricity subsidies.

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 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.

Fossil fuel subsidies do need reform

We would like to express our agreement with two comments, one from Ian Parry who wrote a commentary to our paper in Nature, and another from David Victor in his statement to Scientific American, that there are many reasons to reform fossil fuel subsidies other than emissions reductions. Our article does not cover these reasons and should not be interpreted as a comprehensive assessment of all aspects of subsidy removal.

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.