Nuclear vs renewables: what’s better for climate mitigation?

Wind turbines at sea

This is an adapted version of a blog by Prof Benjamin K. Sovacool and Prof Andy Stirling, to accompany the publication of their paper “Differences in carbon emissions reduction between countries pursuing renewable electricity versus nuclear power” in Nature Energy. A University of Sussex press release also summarises the paper’s findings and policy recommendations.

The role of nuclear power in a low-carbon future has been subject to a long and contentious debate. Is a nuclear or a renewables pathway the best way forward, or do we need a “do everything” approach where every deployable technology is rolled out to decarbonise our electricity supply as soon as possible?

Many influential climate scientists and international organisations argue that a global shift towards nuclear power offers the best pathway to tackling the climate emergency and meeting the world’s increasing demands for electricity.

Others argue that renewable sources of energy are the best pathway towards a low-carbon electricity system and assert that they are cleaner, safer and more economically sustainable than nuclear.

In an attempt to negotiate these contending positions, a frequent mantra is that energy strategies should “do everything” in order to address the climate emergency. But – as a number of commentators have noted (for example, here and here) – this would actually be a highly irrational course of action.

Where “doing everything” involves making investments that are slower or less cost effective, which divert resources away from preferable options, or which in some other way impede them, the result would be potentially disastrous for carbon emissions mitigation.

Amidst many uncertainties, the real questions we should be addressing are about which investments offer the most cost-effective and beneficial ways forward.

Our new paper, Differences in carbon emissions reduction between countries pursuing renewable electricity versus nuclear power, seeks to contribute towards this debate.

Nuclear vs renewable energy – what this paper tells us

Our paper focuses specifically on situations in which real-world constraints mean strategic choices must be made on resource allocation between nuclear or renewables-based electricity.

Our research explores this dilemma retrospectively, examining past patterns in the attachments (i.e. investments) of different countries to nuclear or renewable strategies. Our paper addresses three hypotheses:

  1. A “nuclear climate mitigation” hypothesis: that countries with a greater attachment to nuclear power will tend to have lower overall carbon emissions.
  2.  A “renewables climate mitigation” hypothesis: that countries with a greater attachment to renewables will tend to have lower overall carbon emissions.
  3. A “crowding out” hypothesis: that countries with a greater attachment to nuclear will tend to have a lesser attachment to renewables, and vice versa.

Across the study countries as a whole we found that the “nuclear climate mitigation” hypothesis is not sustained by the evidence at an appropriate level of statistical significance. The renewable climate mitigation hypothesis is confirmed with substantial significance. And the crowding out hypothesis is also significantly sustained.

Put plainly – if countries want to lower emissions as substantially, rapidly and cost-effectively as possible, they should prioritise support for renewables rather than nuclear power. Pursuit of nuclear strategies risks taking up resources that could be used more effectively and suppressing the uptake of renewable energy.

What causes these patterns?

What might explain these patterns? Technologically, nuclear systems have been prone to greater construction cost overruns, delays, and longer lead times than similarly sized renewable energy projects. Thus, per dollar invested, the modularity of renewables projects offers quicker emissions reductions than large-scale, delay-prone, nuclear projects.

Furthermore, renewables tend to display higher rates of positive learning where increased deployment results in lower costs and improved performance, especially for wind farms and solar energy parks. This contrasts with the experience of nuclear power in France which has been prone to negative learning,” rising costs or reduced performance with the next generation of technology.

In terms of policy, the incidents at Three Mile Island (1979), Chernobyl (1986), and Fukushima (2011), all resulted in significant tightening of regulatory requirements for nuclear reactors.

Finally, wider social factors may also work against nuclear energy, and for renewable energy, facilitating faster acceptance, permitting and deployment.

Of course, these are just informed speculations, beyond the scope of the paper itself. Other commentators will favor contrasting interpretations.

But here, perhaps the most important issue – especially given the prominence of the topic and the scale of what is at stake – is that this kind of analysis has been so remarkably neglected over recent years.

Given how highly charged and hotly contested the associated policy controversy is, it is rather strange that there is not a large body of work on these questions. Either way, the many open questions and issues of detail acknowledged in the paper show that much work remains to be done.

The critical importance of independent research – our view

We have presented the findings of our research. Now we must acknowledge the uncertainties and errors, divergent interpretations and clashing interests that make it difficult to achieve the comprehensive prioritising analysis called for at the beginning of this blog – while making a case for the vital importance of scientific scrutiny.

In an ideal world of “evidence-based policy”, energy and climate policy would only go ahead after comprehensive research into every relevant positive or negative aspect of all possible energy resources.

The resulting self-evident “facts” would be examined by objective analysts and any uncertainties eliminated, until a point where a single unambiguous ‘truth’ is determined – with grateful policy makers adopting the identified energy pathway or portfolio.

Unfortunately, we do not live in an ideal world.

Across various energy debates – and not restricted to any political constituency – crucial roles are often played by deliberate mis-representation of information, manipulation of discourse, co-option of leading opposing voices, direct subversion of opponents and stifling of meaningful public debate.

Under conditions like this, the line between advocacy and scholarship (porous at the best of times) can become especially loose when analysts become passionate about their topic. The reasons for such passion can be as trivial as disciplinary identities or sectoral interests, or as deep as wider political ideologies. On all sides “theorising” can be reduced to a search for validation, and “investigation” to the selective collection of data.

Energy debates suffer gravely from these syndromes. “Energy evangelists” on all sides are convinced they have found “the solution” to societies’ energy problems—whether this be solar energy, hydrogen fuel cells or nuclear reactors. The intensity of this advocacy (and the scale of the interests often behind it) can lead to everyone else’s solutions being treated as sacrilegious.

So, exchanges of ideas can become hostile battlefields where proponents are unable to reconcile their underlying differences.

There seems to be an especially pernicious asymmetry in this field. Those whom comparative analysis leads to be generally critical of nuclear power are labelled “anti-nuclear”, whilst no such generally-established terminology exists to the same degree for those who are (entirely legitimately – if debatably) critical of renewable energy.

The situation is aggravated by so much research in this field being (unlike our own) funded (directly or indirectly) by organisations with prior entrenched interests on one side or another.

Despite this, we have often found valued opportunities to bridge the divide with those who hold “opposing” views, but with similar open mindedness and good faith.

It is in this spirit that our analysis is offered. We are open about its background and limitations. We acknowledge that our evidence does not compel only one supposedly definitive interpretation. We are clear about the conditions attached to our own interpretations. By publishing our full dataset and the detailed procedures undertaken in our regression analyses, we offer a basis for others to contest our findings.

The “truth” of our study is in this sense not something arrived at by particular analysts claiming individually-transcendent authority, but by contrastingly-oriented analysts contending with each other in an open and pluralistic way, such as to arrive collectively at more robust understandings. This is the organised skepticism of independent science.

If our analysis stimulates reactions in the same vein, then the cause of scientific scrutiny is reinforced. If, on the other hand, it leads to less qualified assertions and ad hominen labelling, then the chance of bridging the polarised divides is sadly diminished. We hope it will do the former.

Read the paper

Differences in carbon emissions reduction between countries pursuing renewable electricity versus nuclear power
Nature Energy, October 2020

This article was reposted from The Sussex Energy Group blog, by kind permission. Read the original here.


  1. Renewable resources are much better for the environment as it saves new material as well as cost. Renewable energy can be consumed through solar, wind, and water. Thanks for sharing the wonderful information.

    1. What are you even talking about solar and win both rely on battery Banks and capacitors which need to be replaced every three to five years which requires lithium mining Cobalt mining rare Earth metal refining, all of which are some of the worst polluting industries in the world for toxic and heavy chemicals.

      Nuclear energy actually takes up less materials it takes up less land and it puts less pollution into the atmosphere and into the Earth. For all the scare of nuclear waste there’s never been a single leaked cask and the areas that these nuclear waste rods are put into are pretty secure. Not only that but it’s literally just politics which keeps people from running these nuclear rods into less energetic States they could run them down to nearly 50% yield but they’re only allowed to run them down to about 90.

      The answer is clearly both energy sources are valuable and viable and need to be expanded upon but nuclear is the only one that could quote on quote save the world.

      1. Dear Valaska,

        It is because you have a crucial right to express this opinion on energy futures, that we (like the STEPS Centre more widely) underscore so strongly, the importance of democratic struggle in settling the most socially appropriate directions for technology in any given setting.

        But this same imperative raises very difficult questions for those who wish to assert in authoritarian ways (as you do), that those energy pathways that happen to be favoured under their own view, are somehow the only ones that are possible – thus effectively ruling out the values and interests of others.

        It is this monopolising tendency both in nuclear infrastructures themselves, as well as in the scientistic and technocratic style of much of nuclear advocacy, that key empirical results in this article point to. You do not mention that these findings support wider concerns that nuclear tends to ‘crowd out’ other energy pathways.

        To imply in this light as you do, that nuclear simply “has to be part of the mix” (as a matter of dogma) flies in the face of the empirical realities. There are in principle plenty of alternative zero carbon options ready to be pursued instead, if so chosen.

        It also flies in the face of reason. Where these alternatives are acknowledged to perform better, it would be irrational to include a nuclear option that is slower to build, less reliable, more risky, and more expensive.

        If nuclear advocacy were more reasonable and broad minded about being only one option among many (albeit displaying adverse patterns like those documented inn this article), then it might be more persuasive?

        1. So many issues with your argument. The west came to depend on FF for electricity due to irrational fear of nuclear( and quite probably astroturfing by both AE along with O& G industries ).
          So, let’s switch to hydro, wind, and solar. What happens WHEN longs valley or Yellowstone erupt? They will block the sun heavily in north America, and guarantee that we have no power right when we need it.
          Likewise, China is spending lots of money on manipulating weather, including creating clouds.
          From a national security POV, the last thing we want to do, is depend on 1 form of energy. And yes, PV, wind, and hydro are simply different forms of the same energy: solar.
          We need to add new nuclear such as NuScale (Thermal SMRs ), but also fast SMRs, such as natrium and moltex. The last 2 allow ‘spent fuel’ from thermal tractors to be mixed in, and then finish the nuclear fuel cycle.
          We also need to add geothermal power plants as fast as possible. With both longs valley and Yellowstone alone, we power 1/2 of America for 1000+ years, though I would not. basically, we need an energy mix ASAP.

          1. Dear Windbourne,

            We’ve published your comment in interests of openness. But, in the same spirit of honesty, I have to admit that I believe what you say to display a seriously warped grasp of the issues in hand. Anyone reading can judge this for themselves.

            All the best,
            Andy Stirling

  2. Sovacool’s flawed study says more about the author’s prejudices against nuclear than recommendations for climate. The study puts forward correlations based on a limited data set to support its conclusions. It attempts no theoretical basis to explain these correlations, it claims no statistical significance for them, and its conclusions are counter-factual. France has one of the lowest carbon electricity grids in the world thanks to 70% of its generation from nuclear. And how much lower would Germany’s carbon emissions be today if that country had chosen to keep its nuclear units running and phase out coal instead?

    1. Thank you Ian for contributing to this platform for debate. The STEPS Centre is deeply committed to enabling discussion from diverse views – even where we disagree with them.

      It is a shame that this same commitment is not evident more widely. For instance, it is remarkable that before our study, no peer-reviewed simple empirical global survey of associations like this (between nuclear and renewables and actual carbon emissions) has (as far as we can see) been published before.

      That this is a gap, can be acknowledged from any standpoint. Perhaps a clue as to why this gap exists is offered by the shocking intensity and volume of social media responses? Adopting a similar tone to your own comment, a multitude of commentators have sought tarnish this pioneering peer-reviewed study with unsubstantiated opinionated innuendo.

      For instance, you say our study is “flawed”, but do not say why. You say the data is “limited”, even tho’ it’s more comprehensive than any previous study – and certainly much more than has been used in the past to substantiate claims for nuclear power.

      That no final theory is claimed is intrinsic to empirical study. This is a basis for science. If doctrinaire blinkers to the many ways in which nuclear programmes can in fact be implicated in carbon emissions is ‘theory’, then an escape from this is refreshing.

      But, tho’ our study is explicitly correlative rather than causal, we do in fact refer to many literatures covering possible dynamics that might be responsible for the patterns we find. So I am very sorry that your comment is wrong on that count too.

      It remains legitimate to adopt circumscribed foci, as you do in considering electricity grids from a theoretical point of view. But missing embodied emissions, comparative costs and lock-in effects make this a poor basis for the kind of claims you assert.

      In the French and German cases (as others), the crucial rational question is not how much carbon emissions might be reduced by massively expensive nuclear programmes, but what scale these reductions might be if scarce investment were to be assigned instead to more cost-effective renewable options?

      That your comment ignores this – like so much other partisan special pleading – is a worrying syndrome that in itself raises questions about the effects that entrenched nuclear interests are having on rigour and democracy in energy debates.

      The authors of our study have responded in detail to every criticism raised (no matter how spurious) on the Sussex Energy group website here:

      We are also presently responding to a number of rejoinders sent to our publishing journal Nature Energy. So far, despite much hot air, no aspect of our methods or findings has been refuted. With the stakes very high, this is a crucial debate, to which we’re pleased to have been able to help draw attention.

    1. In a spirit of openness we are happy to provide this link to the paper referred to. But I should like to note that it is unfortunate that the authors of this critical commentary did not at any stage seek to solicit any comments from the authors of the paper they attack.

      Also, the paper linked here is a ‘Matters Arising’ piece that the authors have submitted to Nature Energy, which they are now issuing in advance of publication or peer review there – and again without reference to our own response.

      Nature Energy will shortly publish their critique together with our own comprehensive response. Unlike Gilbert et al, we will follow the normal academic practice of awaiting peer review before we issue our reply to them. When it is published, we will link to it here.

      Some of the criticisms raised have – in an earlier form – also been responded to (alongside many other comments) here:

  3. Nuclear power is causing more global warming than fossil fuels fired thermal power per unit power generation. Nuclear power is only cheap and cleaner surrounding. One more thing nuclear power is carbon free and not green house gas free but carbon is not a single factor for global warming. The present crisis of climate change can only recover if we stop all nuclear power and fossil fuel fired thermal power plants.
    IAEA has misguided the entire world by declaring they are cooling the environment by generating nuclear power while environment is getting heated up with generation of nuclear power. They have no well technically qualified persons to guide the group. Only Scientists with half knowledge are misguiding the world’s population.
    Further they have hired many media and journalists to declare this false information for a mental satisfaction with world environment getting destroyed day by day.
    From World Citizens Forum they have been warned to come down to earth from their super flying position from the skies.
    Thanks and regards
    World Citizens Forum
    Bhubaneswar Orissa India.

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