Climate change - caused by emissions of carbon dioxide and other "greenhouse gases" - has been acknowledged as the most severe environmental problem that the UK, and indeed the world, is currently facing.

In the UK, we are falling behind our targets for reducing CO₂ emissions. In fact, emissions rose by over 3% between 2002 and 2004, and are now higher than they were a decade ago. Government projections recognise that we are no longer on track to hit the target for carbon dioxide emissions that we set for 2010. In order to achieve the necessary reductions, it is becoming even more imperative that we are as energy efficient as possible, as well as fully utilising all forms of low carbon energy available to us.

Nuclear energy is the only large-scale provider of low-carbon electricity in the UK, accounting for around 20% of our current electricity production. Over the years, the UK nuclear industry has avoided the emission of 1.6 billion tonnes of carbon dioxide - a major contribution in the fight against global warming. If new nuclear plants are not built in the UK by 2025 we will be virtually without this low-carbon energy supply, as all except one of today's nuclear plants will be closed by then.

Recent Government support for low-carbon generation has focussed on renewables, with the aim of producing 20% of UK electricity from such sources by 2020. However in the recent energy review it has recognised that it is unlikely to make the carbon reductions necessary with these policies alone and that a significant element of nuclear generation needs to remain in our electricity mix in order to cut our emissions sufficiently. Renewable energy (primarily generated by wind turbines) remains a vital part of the fight against global warming, although backup capacity needs to be taken into account. For example wind power relies on fossil-fuelled backup plants to fill in during less windy periods. Renewable energy sources should therefore be seen as complementary to nuclear energy and energy efficiency in the battle against global warming. For maximum impact new renewable generation needs to be replacing carbon dioxide emitting fossil fuel plant not low carbon nuclear.

Although world coal resources could potentially last another 200 years, the CO₂ emitted from coal power stations is approximately double that of gas-fired stations, rendering coal-fired power unattractive from an environmental viewpoint unless there are significant technological developments. While gas as previously stated has lower emissions than coal it can in no way be considered to be a "clean" source of electricity as it still has significant carbon emissions.

There has been much discussion recently over the amount of carbon dioxide emitted from the overall nuclear energy cycle, including power station construction, uranium mining and enrichment, fuel manufacture, transport, waste management and so on. Probably the most comprehensive review of lifecycle carbon emissions has been the recent Parliamentary Office of Science and Technology report which made an evaluation of all studies available worldwide. This clearly shows that the lowest lifecycle emissions are from nuclear and on-shore wind. Even other renewables such as solar panels are up to ten times higher than this and gas stations are 100 times greater with coal double that (the studies results are shown below):

• Coal 800-1000 g/kWh
• Gas 400 g/kWh
• Biomass 25-93 g/kWh
• Photovoltaic 58 g/kWh
• Marine 25-50 g/kWh
• Hydro 5-30 g/kWh
• Wind 5 g/kWh
• Nuclear 5g/kWh

The exact figure for any power station depends on the particular mines from which the uranium fuel comes, as well as the technology used for enrichment and other operational considerations. However a specific study for British Energy's Torness station shows that even when all of these indirect emissions are included, this nuclear station's emissions are 5g/kWh, so it can produce power with only around one-hundredth of the CO₂ emissions of fossil fuels such as coal or gas.

The total amount of carbon dioxide emissions from the UK in 2003 was 560 MtCO₂. If the electricity generated by nuclear was replaced by coal, emissions would rise by 14%. However, it is more likely that retiring nuclear power stations will be replaced with gas fired generation. Gas is often considered the green option but if that were to happen UK emissions would be nearly 6% higher.