Greenhouse gases explained: what are they, and why are they so bad for the planet?

16 June 2021 | Aimee Tweedale

Ever walked into a greenhouse on a warm summer’s day and instantly broken out in a sweat? That’s because greenhouses are brilliant at holding onto heat. And that’s exactly what greenhouse gases do, too! 

These gases are great for keeping our planet warm. But too much of them leads to too much warmth – which leads to climate change

What are greenhouse gases?

That’s why you’ll have heard lots of talk about cutting down our greenhouse gas emissions in the news lately. 

But what actually are greenhouse gases, where do they come from, and how do they cause the greenhouse effect? Read on, for everything you need to know. 

What are greenhouse gases?

Greenhouse gases are gases that trap warmth. As sunlight beams down onto earth, greenhouse gases grab onto the heat from the sun’s rays, and stop it from leaving the atmosphere.

Most greenhouse gases are naturally-occuring, but some are man-made. You might sometimes hear them referred to as “GHG” for short. 

Greenhouse gases trap warmth in the earth's atmosphere

Examples of greenhouse gases: 5 major greenhouse gases

There are lots of different types of greenhouse gas out there in our atmosphere. But these are the 5 big names you need to know.

Carbon dioxide

Known as “CO2” or just “carbon” for short, carbon dioxide is the greenhouse gas we all hear the most about. 

And for good reason. In 2019, it accounted for 80% of the UK’s total greenhouse gas emissions1

Carbon dioxide is released when we burn fossil fuels, like coal, oil, and gas. It’s also released when we burn natural materials like wood, and from some chemical reactions. In its solid form, you might know it as dry ice!

In the right quantities, carbon is a part of the natural cycle of life on earth. Plants absorb it, and turn it into oxygen, in the process of photosynthesis. 


There’s less methane being pumped into our atmosphere than carbon dioxide. Even so, it’s 28 times more effective than carbon dioxide at heating the earth, which means it has a powerful influence2.

Methane comes from lots of natural sources, like microbes that live in wetlands and bogs. It also – famously – comes from grazing cows passing wind!

Because there are so many cows being bred for meat and dairy today, scientists estimate that this accounts for about 40% of methane emissions globally. It also comes from other human activities, like growing rice, and drilling for oil or gas3

Nitrous oxide

You’ve probably heard of this one by its more common name: laughing gas!

Nitrous oxide is emitted from lots of human activities, including combustion of fossil fuels, and wastewater treatment4. In 2019, it made up 5% of the UK’s total GHG emissions5.

Note: nitric oxide and nitrogen dioxide are not greenhouse gases. 

Fluorinated gases

Sometimes called F-gases, this is a collection of man-made greenhouse gases that are released in smaller quantities than the others on this list, but have a very strong effect. In fact, their global warming effect can be up to 23,000 times stronger than carbon dioxide6!

The most common of the F-gases are hydrofluorocarbons. These are released into the atmosphere by things like commercial fridges and air-conditioning units. 

PFCs, or perfluorocarbons, are found in lots of electronic devices and cosmetics. 

The EU has vowed to cut emissions of F-gases by 2 thirds by 20307

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Water vapour

Water vapour is the most abundant greenhouse gas in our atmosphere. So why don’t we hear about it as much as the others?

There are 2 good reasons:

  1. Water vapour doesn’t hang around in the atmosphere for years, like other greenhouse gases – it’s usually gone within days
  2. And it doesn’t come directly from human activity, so it’s not generally counted as part of our greenhouse gas emissions

In fact, water vapour is actually a natural byproduct of the atmosphere being hotter. So when we release more greenhouse gases like carbon or F-gases, and the temperature heats up, more water vapour is created8

This can contribute to there being more clouds in the sky!

Where do greenhouse gases come from?

Greenhouse gases are released into the atmosphere in lots of different ways, but the majority come from the burning of fossil fuels. 

Here’s a breakdown of the sectors that created the most GHG emissions in the UK in 2019:

  • Transport, 27%: this includes road vehicles, trains, shipping, and flights
  • Energy, 21%: this is mainly due to fossil fuels being burned to generate electricity and heat
  • Business, 17%: these emissions come from things like industrial machinery, air-conditioning, and refrigeration
  • Residential, 15%: this represents the emissions we generate by heating our homes, and using natural gas for cooking
  • Agriculture, 10%: these emissions come from the machinery and livestock involved in farming 
  • Waste management, 4%: this comes from landfills, where our waste is either being treated, burned, or releasing emissions as it decomposes

To see the full breakdown, take a look at the government’s report.

A plane flying over a forest

What is the greenhouse effect?

The greenhouse effect is the name that’s given to the way that greenhouse gas emissions heat up the earth’s atmosphere.

Like greenhouse gases themselves, the greenhouse effect is a natural process. We need the greenhouse effect to keep the earth at a cosy average of 15C. That’s what makes life on earth possible9!

But the problem comes when there are too many greenhouse gases in the atmosphere. That causes temperatures to rise more than they should. You might have heard this referred to as “the enhanced greenhouse effect” – or, more commonly, global warming. 

Consequences of the enhanced greenhouse effect

Usually, the greenhouse effect is responsible for keeping earth at just the right temperature.

But with too many greenhouse gases in the atmosphere, that temperature is going up. The earth has warmed by an average of 1C since pre-industrial times.

And the heat is only rising more rapidly. It’s been reported that 2014 to 2018 were the hottest 5 years globally that have ever been recorded10.

Why does this matter? Because global warming can have some devastating consequences. If we don’t limit the average temperature of our planet, to stop it heating by more than 1.5C, we could face:

  • Extreme weather events like heatwaves, droughts, wildfires, hurricanes, and floods
  • Rising sea levels
  • Changing biodiversity (which means some species could be wiped out)
  • Difficulty growing crops, which could lead to food shortages
  • More insects spreading deadly diseases

These are just a few examples. Read more in our complete guide to climate change and its causes and effects.

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What can we do about the greenhouse effect?

To fight the effects of climate change, we all need to do everything we can to cut our greenhouse gas emissions. That’s why the UK government has announced a target of net zero greenhouse gas emissions by 205011.

This will need to be a collective effort from different sectors, like manufacturing, agriculture, and transport. The energy industry has a big role to play. Here in the UK, the energy we use to heat buildings and provide hot water alone accounts for 15% of our GHG emissions12

Changing this will be a huge challenge, and it’s one we’re taking seriously. Check out what we’re doing at OVO to reach our goal of net zero emissions.

On a smaller level, there are also some day-to-day things you can do to limit your own GHG emissions. The climate crisis is bigger than all of us, but we can each do our part to make greener choices. That might mean swapping your car for a bike, or turning your heating down by 1 degree.

Looking for more ideas on how to reduce your carbon footprint? We’ve got lots of guides to help you get started:

Choose OVO to power your greener home

Your home energy makes up a mighty 28% of your personal carbon footprint13

With OVO, you can rest easy knowing that you’re getting 100% renewable electricity14. Plus: we’ll plant 1 tree in your name every year15, and give you access to OVO Greenlight, our nifty energy-saving tool

And, if you want to go even further, our green upgrade OVO Beyond comes with 100% carbon-neutral energy (including 15% green gas – one of the best mixes you can get in the UK)16. We’ll also plant 5 extra trees for you each year. 

Ready to join us on the journey of a lifetime to net zero? Hit the button below, to get a quote in under 2 minutes. 

Sources and references:













13 Based on analysis carried out by the Carbon Trust for OVO Group (2020), 28% of an average individual’s carbon footprint in the UK comes from energy. In this analysis, the carbon footprint includes the following lifestyle categories: energy, transport, shopping, food and drink and holidays. See table below for each category. This carbon footprint data has been calculated using BEIS 2020 emission factors. This excludes emissions from things that the average person cannot directly control such as supporting the NHS, defence, government bodies, etc. Please note these figures are not reflective of potential changes to your habits during the coronavirus pandemic.

14 100% of the renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on Renewable Energy Guarantee of Origin certificates and how these work. A proportion of the electricity we sell is also purchased directly from renewable generators in the UK.

15 Each year, OVO plants 1 tree for every member in partnership with the Woodland Trust. Trees absorb carbon dioxide from the atmosphere, so tree-planting helps to slow down climate change.

16 Enjoy even greener energy with OVO Beyond in comparison with our standard OVO plans. In addition to 100% renewable electricity as available with our standard plans, OVO Beyond reduces your yearly carbon emissions from the energy used in your home that is supplied by OVO to net zero by providing 100% carbon-neutral gas (15% green gas and 85% offset) and offsetting all associated lifecycle carbon emissions involved in the production and consumption of your electricity & gas, you will also get 5 trees per year in UK schools and communities and other green benefits. The renewable electricity we sell is backed by renewable certificates (Renewable Energy Guarantee of Origin certificates (REGOs)). See here for details on Renewable Energy Guarantee of Origin certificates and how these work. The green gas we sell is backed via renewable certificates (Renewable Gas Guarantees of Origin (RGGOs)). See here for details on Renewable Gas Guarantees of Origin and how these work. A proportion of the electricity we sell is also purchased directly from renewable generators in the UK. We offset the remaining emissions by supporting UN REDD+ carbon reduction projects that are certified to the Verified Carbon Standard or the Gold Standard. See here for more information on how we restore nature and protect rainforests with our offsetting programmes.

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