Understanding Greenhouse Gases: From Kyoto to Net Zero

When discussing climate change, greenhouse gases (GHGs) are central to the conversation. But these gases are not all equal in their impact, and tackling climate change effectively means understanding the full picture.

The Kyoto Protocol, adopted in 1997, was the first international agreement to formally recognise seven key greenhouse gases as the primary contributors to human-driven global warming. While Kyoto was a landmark moment in global climate diplomacy, the UK has since set its own legally binding targets under the Climate Change Act 2008 (as amended), including a commitment to reach Net Zero emissions by 2050.

The Main Greenhouse Gases

Of the seven GHGs listed under the Kyoto Protocol, the most widely known is carbon dioxide (CO₂). It serves as the baseline for comparing the warming impact of other gases, with a Global Warming Potential (GWP) of 1. CO₂ is primarily emitted through the burning of fossil fuels (for electricity, heating, and transport), industrial processes, and land use change. It is also the most abundant anthropogenic GHG and has a long atmospheric lifetime—some of it remains for thousands of years.

However, methane (CH₄) and nitrous oxide (N₂O), though emitted in smaller quantities, have much higher GWPs:

Methane has a GWP of around 28–36 over a 100-year timeframe and a shorter atmospheric lifetime (~12 years), but is over 80 times more powerful than CO₂ over 20 years.

Nitrous oxide has a GWP of approximately 298 and an atmospheric lifetime of over a century. It is predominantly released from agricultural practices, such as fertiliser application.

In addition to these, the Kyoto Protocol includes:

• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)
• Sulphur hexafluoride (SF₆)

These synthetic gases are used in refrigeration, electronics, and industrial applications, and can have GWPs in the thousands or tens of thousands. Their long atmospheric lifetimes and high warming potentials make them significant targets for reduction, particularly in sectors like HVAC and manufacturing.

Policy and Responsibility

The UK has made substantial progress in reducing emissions, especially from the power sector. However, emissions from agriculture, buildings, and transport remain significant, and require coordinated multi-gas mitigation strategies.

The Climate Change Committee (CCC), which advises the UK Government, has emphasised the importance of tackling all GHGs - not just CO₂. Methane reduction from livestock, improved nitrogen use in farming, and reducing leakage of refrigerant gases are all necessary to meet our legally binding carbon budgets.

The UK Emissions Trading Scheme (UK ETS), which replaced the EU ETS post-Brexit, also includes many of these GHGs, offering a market-based mechanism for emissions reduction.

Why Multi-Gas Mitigation Matters

Relying solely on CO₂ reductions will not be enough to meet Net Zero targets. A truly effective response requires understanding the relative impacts, sources, and lifetimes of all major GHGs.

At Tomson, we help local authorities, developers, and infrastructure providers assess and reduce emissions across a wide range of sectors. From low-carbon heat network planning to sustainability strategy and environmental reporting, we support holistic approaches to decarbonisation aligned with UK policy and funding frameworks.

Want to develop a Net Zero strategy that tackles emissions from all major sources? Get in touch with our team of specialists to find out how we can support your organisation.