Nuclear power is often promoted as one of the best ways to reduce our reliance on fossil fuels to generate the electricity we need, but new research suggests that going all-in on renewables such as wind and solar might be a better approach to seriously reducing the levels of carbon dioxide in the atmosphere.

Based on an analysis of 123 countries over a quarter of a century, the adoption of nuclear power did not achieve the significant reduction in national carbon emissions that renewables did – and in some developing nations, nuclear programmes actually pushed carbon emissions higher.

The study also finds that nuclear power and renewable power don't mix well when they're tried together: they tend to crowd each other out, locking in energy infrastructure that's specific to their mode of power production.

Given nuclear isn't exactly zero carbon, it risks setting nations on a path of relatively higher emissions than if they went straight to renewables.

However, it's too early to rush to a judgement on nuclear just yet.

It's important to note that the study looked specifically at data from 1999-2014, so it excludes more recent innovations in nuclear power and renewables, and the scientists themselves say they have found a correlation, rather than cause and effect. But it's an interesting trend that needs further investigation.

"The evidence clearly points to nuclear being the least effective of the two broad carbon emissions abatement strategies, and coupled with its tendency not to co-exist well with its renewable alternative, this raises serious doubts about the wisdom of prioritising investment in nuclear over renewable energy," says Benjamin Sovacool, a professor of energy policy at the University of Sussex in the UK.

"Countries planning large-scale investments in new nuclear power are risking suppression of greater climate benefits from alternative renewable energy investments."

The researchers suggest the tighter regulations and longer lead times associated with nuclear power are responsible for some of the statistics explored here, while the large-scale development that nuclear requires tends to leave less room for renewable projects that work on a smaller scale.

There are also broader considerations to weigh up – nuclear and renewables will be two factors among many in the policies put together by governments when it comes to reducing carbon emissions.

Plus, given the time frame, a lot of the nuclear power plants covered by this study are likely to have been getting towards the end of their lifespans, which means more energy is required to maintain them.

Whatever the ins and outs of the nuclear policies, the study does show a clear link between greater adoption of renewable projects and lower carbon emissions overall.

The study authors propose that by cutting out nuclear altogether, these renewable gains could be even greater.

"This paper exposes the irrationality of arguing for nuclear investment based on a 'do everything' argument," says researcher for technology policy Andrew Stirling at the University of Sussex.

"Our findings show not only that nuclear investments around the world tend on balance to be less effective than renewable investments at carbon emissions mitigation, but that tensions between these two strategies can further erode the effectiveness of averting climate disruption."

It's a more contentious issue than you might think.

Many scientists (and Bill Gates) say that nuclear energy is our only option at this point, maintaining a view that it can replace fossil fuels with efficiencies that renewables can't match right now.

A study from 2018 also concluded that nuclear power has to be an essential part of the mix if we're going to reduce the temperature of the planet by as much as we need to – at least until options like wind and solar have had time to scale up.

Work continues to make nuclear a leaner, more agile source of energy that can better operate alongside renewable projects, which will help it improve on the figures in this study.

In the meantime, the study authors are asking for more detailed reports from the nuclear industry, in order to better understand its benefits.

"While it is important to acknowledge the correlative nature of our data analysis, it is astonishing how clear and consistent the results are across different time frames and country sets," says Patrick Schmid, from the ISM International School of Management in Germany.

"In certain large country samples the relationship between renewable electricity and CO2-emissions is up to seven times stronger than the corresponding relationship for nuclear."

The research has been published in Nature Energy.