100% Renewables – A Few Remarks about the Jacobson/Clack Controversy

François-Xavier Chevallerau

The scientific debate about the feasibility of a full transition to renewable energy is suddenly becoming heated. Yet it may somehow be missing the point.

new paper published last week in the Proceedings of the National Academy of Sciences (PNAS), one of the world’s most prestigious peer-reviewed science journals, has sparked a furious row between prominent scientists over the feasibility for the United States – and the world – to run on 100% renewable energy.

Authored by a group of 21 academic and private energy researchers led by Christopher Clack from the University of Colorado, the paper evaluates and refutes a previous study published in 2015 in the same journal by a group of researchers led by Mark Jacobson from Stanford University, and which claimed that a transition to 100% wind, water, and solar (WWS) power for all purposes (electricity, transportation, heating/cooling, and industry) could be achieved in the continental United States between 2050 and 2055, at low cost. The new paper argues that the Jacobson team’s ‘low cost solution’ proposal “involves errors, inappropriate methods, and implausible assumptions”, and would actually impede rather than enable “the move to a cost effective decarbonized energy system” if it was adopted and implemented. The most feasible route to a low-carbon energy future, the Clack team says, is one that adopts “a diverse portfolio of technologies” – i.e. including nuclear and carbon capture and storage (CCS) – instead of relying solely on renewables.

Following the publication of the Clack et al. paper, a fierce controversy erupted between the two teams of researchers and their respective supporters in the scientific community. A counter-rebuttal was immediately issued by the Jacobson side, followed by a counter-counter-rebuttal by the Clack side, both refuting the other side’s arguments or motives out of hand and in unusually harsh terms. The two sides accused each other of dishonesty or incompetence, or of serving lobbies or vested interests, and engaged in a Twitter battle as has rarely or maybe even never been seen before between serious scientists.

This spectacle of high-level scientists engaging in ‘tweetstorms’ and aggressive rebuttals of each others’ perspectives is unlikely to be very beneficial to the cause of the energy transition, and could even provide ammunitions to those who oppose it. Among policy makers, even those who are positively predisposed towards renewable energy, it may instill doubts about the soundness of the science underpinning the efforts to promote and accelerate the energy transition.

More importantly, this kind of heated discussion about the technical feasibility and possible pathways to 100% renewable energy might somehow be missing the real point of the energy transition, and could thus be counterproductive. Of course, some scientific evidence of the technical feasibility of a ‘decarbonization’ of the economy is needed, as this decarbonization requires making policy choices that will have profound and lasting economic and social consequences. However, trying to elaborate detailed technical assessments, scenarios and roadmaps for a move to 80%, 90% or 100% renewables is probably somewhat futile at this stage, and may even obscure rather than inform the conversation that societies, in the U.S. and elsewhere, need to have.

In fact, the ‘feasibility’ of a full-scale transition to renewable energy is only partly, and probably not primarily, a technical matter.

Full decarbonization, it should be remembered, requires that zero-carbon energy sources not only supplant currently dominant energy sources in relative terms – which is what happened in previous ‘energy transitions’ – but literally replace them in absolute terms – something that is without any known precedent. Over the last few centuries, new energy sources have always, when being deployed, supplemented rather than replaced or substituted preexisting ones. When coal supplanted biomass and water power as the the world’s dominant energy source in the 19th century, we didn’t stop using biomass and water power – in fact we’re using more of them now than ever before. When petroleum supplanted coal as the the world’s dominant energy source in the 20th century, we didn’t cease using coal – in fact we’re using more of it now than ever before.


Development of the world’s total energy consumption split by source from 1800 to 2013. Historically, various energy sources have not replaced but added up to each other to meet a total energy consumption that has been rising sharply since the Industrial Revolution and that keeps rising. Source: Nate Hagens and Rune Likvern, Fractional Flow

Therefore, the expected partial or total replacement this century of fossil fuels by renewables, in absolute terms, is something that cannot be compared with previous energy transitions. It represents far more than just the technical replacement of a set of energy sources by another set of energy sources, and amounts to a full-scale ‘re-engineering’ of human civilization’s ‘metabolism’, i.e. the set of processes by which human societies – and their various components – ‘exchange’ energy and matter with their biophysical environment and between themselves, and use them in various ways and for various purposes. The only relevant precedents in human history are the transition from hunting and gathering societies to agricultural societies, and then the transition from agricultural societies to fossil fuel-based industrial societies.

Even with the best intentions, it is difficult to envisage that such a transition could take place without requiring and/or triggering far-reaching societal, economic, and political changes, which will deeply affect societies’ organizations, economic models, political balance of power, but also their technical capabilities. It is difficult to envisage that it could take place without profoundly ‘disrupting’ our existing political, economic, financial and social systems, and triggering a number of positive and negative feedbacks that we can hardly foresee and probably not model at this stage. It is difficult to envisage that this process could be anything but messy, destabilizing, risky, with a high potential for brutal or even violent disruptions. And it is difficult to envisage that it could be completed at ‘low cost’ in a matter of just a few decades.

There is obviously a natural tendency in Western societies, among policy makers and also in civil society, to wish that the transition to renewables can be done, that it can be done quickly, and that it can be done relatively painlessly, i.e. without affecting too much the essence of the social, political and economic setup we are used to, or the balance(s) of power that are ingrained in it. Hence a favorable disposition towards scientists coming up with seemingly robust models showing that a clear and quick pathway towards 100% renewable energy exists, and proposing a roadmap to get there. This is somehow reassuring, and this is actually what a lot of us want to hear and to believe.

Yet, scientific studies that focus solely or mostly on the technical feasibility of a full-scale transition to renewables are probably inherently misleading, as they are based on technical and economic assumptions and models that are likely to be made invalid, obsolete or irrelevant by the set of societal, economic, political and technical changes that the transition process itself will set in motion. These kinds of studies may in fact have the effect of obscuring rather than shedding light on the stakes of the transition, by drowning them into complex models and calculations that few outside very limited scientific circles can really comprehend and appraise. This could lead to a backlash if and when it appears that the process does not unfold as these studies said it would. Paradoxically, these kinds of studies may also increase the risk of somehow ‘trivializing’ the debate about the energy transition. This debate is or should be, first a foremost, a political debate, and the outcome of the transition will depend, first and foremost, on how we will manage to design, implement, and sustain new economic, social and political balances of power, within and between countries. This, much more than the accuracy of technical roadmaps that we may be able to design today, will determine whether, how and how successfully we will be able to transition to renewables.

Therefore, a variety of dimensions should, as much as possible, be taken into consideration in studies that are intent on assessing the feasibility – including the technical feasibility – of a full decarbonization of the economy. This would probably require a more systematic and far-reaching integration of interdisciplinarity in such studies, and the elaboration of modular, multi-layered scenarios rather than of detailed technical pathways or roadmaps.

In the meantime, the debate goes on…

originally published by Biophysical Economics Policy Center


For those interested in the details of the Jacobson/Clack row, the following articles provide useful information:

Can the U.S. Grid Work with 100% Renewables? 

The Clean Energy Debate Is Fueling One of the Most Vitriolic Fights in Science Publishing

Fisticuffs Over the Route to a Clean-Energy Future

Can the world run on clean power? Scientists clash

Energy wonks have a meltdown over the US going 100 percent renewable. Why?