What are greenhouse gases?

During the day, the sun shines through the atmosphere, warming the earth’s surface. At night, earth's surface cools, releasing heat back into the air. But some of the heat is trapped by the greenhouse gases in the atmosphere. That's what keeps the earth’s temperature at an average 14˚C (57˚F). The gases act like the glass walls of a greenhouse – hence the name, greenhouse gases. Without this greenhouse effect, temperatures would drop to as low as -18˚C (-0.4˚F); too cold to sustain life on earth.

But human activities are changing earth's natural greenhouse effect with a dramatic increase in the release of greenhouse gases. Scientists agree greenhouse gases are the cause of global warming and climate change.

Since the Industrial Revolution of the late 1700s and early 1800s, humans have been releasing larger quantities of greenhouse gases into the atmosphere. That amount has increased dramatically in the past century, with the knock-on effect of global warming. Global temperatures have accelerated in the past 30 years and are now the highest since records began.

What are the specific greenhouse gases?

• Carbon dioxide (CO₂) is released through natural processes, such as volcanic eruptions, plant respiration and animals and humans breathing. But the atmospheric CO₂ concentration has increased by 47% since the Industrial Revolution began in the 1800s, due to human activities like the burning of fossil fuels and large-scale deforestation. Due to its abundance, CO₂ is the main contributor to climate change.
• Methane is a gas produced naturally through decomposition. But again, human activity has displaced the natural balance. Large amounts of methane is released by cattle farming, landfill waste dumps, rice farming and the traditional production of oil and gas.
• Nitrous oxide is a greenhouse gas produced through the large-scale use of commercial and organic fertilisers, fossil-fuel combustion, nitric-acid production and biomass burning.
• Water vapour is the most abundant greenhouse gas. Water vapour increases as the earth's atmosphere warms but unlike CO₂, which can remain in the earth’s atmosphere for centuries, water vapour persists for a few days.

The group of gases detailed above are naturally produced, but their increasing atmospheric concentration is man-made.

In contrast, the three industrial fluorinated gases – hydrofluorocarbons (HFC), perfluorocarbons (PFC) and sulphur hexafluoride (SF₆) – are solely man-made during industrial processes and do not occur in nature. Though they are present in very small concentrations in the atmosphere, they trap heat very effectively, meaning they are extremely potent.

SF₆, which is used in high-voltage electricity equipment, has a ‘Global Warming Potential’ 23,000 times greater than CO₂.

What can be done to reduce greenhouse gases?

Greenhouse gases can be reduced by phasing out fossil fuels, such as coal, oil and gas, and moving to renewable energy, such as solar and wind.

We can all play a part in protecting our planet, from simple daily changes, like reusing and recycling, to bigger lifestyle decisions like switching to electric vehicles.

What are we doing to reduce greenhouse gases here at National Grid?

Helping society to decarbonise is the biggest contribution we can make to the environment. This means working towards the connection of low-carbon, renewable energy sources across the UK and US, and achieving the technical capability of operating a zero-carbon electricity system.

We are committed to achieving net zero by 2050.

We are a principal partner of COP26, the global climate summit conference to be hosted in Glasgow in November 2021.

The conference will be the most significant climate event since the 2015 Paris Agreement – when all parties to the UNFCCC agreed to keep the average global temperature increase to well below two degrees and to try to limit it to 1.5 degrees. At COP26, governments around the world will be reporting on their countries’ progress and agreeing to new actions to cut carbon emissions.

We are proud of what we have achieved to date, but there is much more we can do. We believe we have a responsibility to lead the way and help drive emissions down across the energy sector.

In our own businesses, our ambition is to eliminate all SF₆ gas from our assets by 2050. In the UK, the NGESO will aim to operate a zero-carbon system by 2025.

In addition, in the UK, our Electricity Transmission business has set a target to achieve carbon-neutral construction by 2026 on all projects, while Gas Transmission is applying this target to all major projects.

We are moving to a 100% electric fleet by 2030 for our light-duty vehicles and pursuing zero carbon alternatives for our medium and heavy-duty vehicles.

In the US, all our major projects use carbon pricing in the evaluation of alternative options. In 2021, we will be developing a baseline carbon intensity for such projects, with the aim of setting reduction targets beginning in 2022.

Energy explained