

All four of us have dedicated our scientific careers to understand the processes and impacts of climate change, variously studying ocean systems, tropical cyclones, ice sheets and ecosystems as well as impacts on human societies. We have used both climate models and geological records of past climates to better understand lessons from warmer periods in the Earth’s history and investigate future scenarios.

We have become so concerned about humanity’s slow response to this challenge that we have decided we must clearly set out what we see as the only viable path forward. As scientists we do not take advocacy positions lightly, but we believe the magnitude of climate change now presents an unprecedented moral challenge that compels us to speak out.

To avoid the worst effects of climate change, including continued sea level rise, the total loss of Arctic sea ice and devastating effects on human societies and natural ecosystems alike, rapid global decarbonisation is needed. The voluntary measures put on the table at Paris by over 100 nations are a welcome step, but unless there are strong measures to reduce emissions beyond 2030, global emissions would remain at a high level, practically guaranteeing that young people inherit a climate running out of their control. A new and intensified approach is clearly needed.

Everyone agrees that the most urgent component of decarbonisation is a move towards clean energy, and clean electricity in particular. We need affordable, abundant clean energy, but there is no particular reason why we should favour renewable energy over other forms of abundant energy. Indeed, cutting down forests for bioenergy and damming rivers for hydropower – both commonly counted as renewable energy sources – can have terrible environmental consequences.

Nuclear power, particularly next-generation nuclear power with a closed fuel cycle (where spent fuel is reprocessed), is uniquely scalable, and environmentally advantageous. Over the past 50 years, nuclear power stations – by offsetting fossil fuel combustion – have avoided the emission of an estimated 60bn tonnes of carbon dioxide. Nuclear energy can power whole civilisations, and produce waste streams that are trivial compared to the waste produced by fossil fuel combustion. There are technical means to dispose of this small amount of waste safely. However, nuclear does pose unique safety and proliferation concerns that must be addressed with strong and binding international standards and safeguards. Most importantly for climate, nuclear produces no CO2 during power generation.

To solve the climate problem, policy must be based on facts and not on prejudice. The climate system cares about greenhouse gas emissions – not about whether energy comes from renewable power or abundant nuclear power. Some have argued that it is feasible to meet all of our energy needs with renewables. The 100% renewable scenarios downplay or ignore the intermittency issue by making unrealistic technical assumptions, and can contain high levels of biomass and hydroelectric power at the expense of true sustainability. Large amounts of nuclear power would make it much easier for solar and wind to close the energy gap.

The climate issue is too important for us to delude ourselves with wishful thinking. Throwing tools such as nuclear out of the box constrains humanity’s options and makes climate mitigation more likely to fail. We urge an all-of-the-above approach that includes increased investment in renewables combined with an accelerated deployment of new nuclear reactors.

For example, a build rate of 61 new reactors per year could entirely replace current fossil fuel electricity generation by 2050. Accounting for increased global electricity demand driven by population growth and development in poorer countries, which would add another 54 reactors per year, this makes a total requirement of 115 reactors per year to 2050 to entirely decarbonise the global electricity system in this illustrative scenario. We know that this is technically achievable because France and Sweden were able to ramp up nuclear power to high levels in just 15-20 years.

Nuclear will make the difference between the world missing crucial climate targets or achieving them. We are hopeful in the knowledge that, together with renewables, nuclear can help bridge the ‘emissions gap’ that bedevils the Paris climate negotiations. The future of our planet and our descendants depends on basing decisions on facts, and letting go of long-held biases when it comes to nuclear power.