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Is Water Vapor a Greenhouse Gas?

EcologyGlobal Warming

Level

Stephanie Safdie

updated 2 Sept 2024

US Copywriter at Greenly

In today’s society, next to everything we do contributes to greenhouse gas emissions – leading some people to wonder how water vapor is a greenhouse gas that also contributes to global warming.

Water vapor refers to water in its gaseous form when it is below boiling temperature – such as with a boiling teapot where the excess steam evaporates into the air. However, most people do not realise that this is a consequence of climate change.

In this article, we’ll review what greenhouse gasses are, how is water vapor a greenhouse gas, and how we can reduce the amount of water vapor contributing to global warming.

What are greenhouse gasses?

Greenhouse gasses, also referred to as GHG emissions, refer to the heat trapped in the atmosphere as a result of excessive industrial activity.

“ Greenhouse gasses are one of the main contributors to global warming, as it contributes to the greenhouse gas effect that is contributing to climate change itself. ”

sSome examples of greenhouse gasses include:

Carbon dioxide (CO₂)
Methane (CH₄)
Nitrous Oxide (N₂O)
Industrial Gasses
Hydrofluorocarbons (HFCs)
Perfluorocarbons (PFCs)
Sulfur hexafluoride (SF6)
Nitrogen trifluoride (NF3)

Although common in our daily lives as a result of increased aviation travel, industrial processes, and single use products – it is important for all of us to remain cognisant of the effects of greenhouse gas emissions and how they continue to affect our environment.

👉 Unbeknownst to most, water vapor is the most abundant greenhouse gas – despite the fact that many scientists believe that water vapor produced by humans has an impact on the amount of water vapor greenhouse gasses in the atmosphere.

What is water vapor?

Water vapor, more oftenly referred to as steam, is water in its evaporated state – which is when water vapor mixes with the surrounding air and “disappears” before your eyes.

💡 However, in reality – that water vapor is increasing not only the humidity, but the temperature of the surrounding air. This is often why many people will choose to open a window when taking a shower or ensuring proper ventilation in the kitchen to avoid a room from getting too hot and humid.

“ The most common example of water vapor refers to steam, such as a boiling pot of water where water vapor then escapes from the pot into the surrounding air. ”

Some examples of water vapor include:

Steam – Whether it's boiling a pot of water for pasta, entering a sauna, or taking a hot shower – steam is the most commonly referred to example of water vapor.
Clouds and Fog – Think of San Francisco on a typical gray morning – that fog over the Golden Gate Bridge is made of small droplets of water, and formed after water vapor condenses.
Exhaling in Cold Weather – When you exhale, the moisture in your breath condenses in cold air, making water vapor visible.
Humidity – On a humid day, there is a high amount water vapor in the air – meaning if you’ve ever wondered why the air seems to be more “wet” on a humid day, it’s because there is actual water in the air – just in a different state of matter.
Evaporation from Lakes and Ocean – Water vapor frequently enters our atmosphere as a result of sunlight hitting large bodies of water. This is one of the reasons why rising sea levels could be concerning – as the more water there is, the more water will evaporate into the air.

👉 Overall, water vapor is essential for the water cycle and is a massive contributor in greenhouse gas emissions.

What is the water cycle?

The water cycle refers to how water can shift between various states of matter, such as a solid, liquid, or gas. It is important to note that water is the only substance on Earth that can easily change from one state of matter to another, and as a result – water vapor

💡 Remember, when it comes to how water vapor affects climate change, it is detrimental when in a gaseous state of matter.

Water can change into various states of matter via:

Melting
Sublimation
Freezing
Condensation
Evaporation

Process	Description
Melting	The process where solid water (ice) changes into liquid water as heat is absorbed.
Sublimation	The transformation of solid water (ice) directly into water vapor, bypassing the liquid phase.
Freezing	The process where liquid water changes into solid ice as it loses heat.
Condensation	The process where water vapor cools and changes into liquid water, forming droplets.
Evaporation	The transformation of liquid water into water vapor as it gains heat energy.

All of these changes require a transfer of energy, as regardless of the state of matter the water is currently in – the water particles must be absorbed or released to evolve into another state of matter.

👉 In the event of how water vapor can act as a greenhouse gas, the transfer of energy on behalf of the water particles creates heat – which is why water vapor and evaporation can be classified as a greenhouse gas itself.

What is the global warming potential of water vapor?

The global warming potential of water vapor is catastrophic, seeing as water vapor remains one of the most abundant and powerful greenhouse gasses in the atmosphere. However, it is important to note that water vapor doesn’t have the same fixed GWP as other greenhouse gasses.

“ According to a study by IOP science from September 2018, the global warming potential (GWP) of water vapor is H2O of −10−3 to 5 × 10−4 – which in simple terms, means that larger increases in water vapor emissions would have a small impact on global warming. ”

💡Therefore, water vapor doesn’t have a fixed GWP in the same way as other greenhouse gasses such as carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). Regardless, the impact of water vapor greenhouse gasses is still worthy of our attention.

Here are a few reasons why water vapor can still have a reasonable impact on global warming and help us to understand the increase in atmospheric temperatures:

Dynamic Concentration – It is important to know that water vapor concentration is not directly influenced by human activity, but more so by how it changes from one state of matter to another – such as via evaporation and condensation. However, the warmer that the air does get as a result of other excess greenhouse gas emissions – the more water vapor that will be held in the air. Therefore, the GWP of water vapor is contingent on the amount of other GHG emissions currently being produced.
Feedback Mechanism – Water vapor acts as more of a signal than a direct cause. In other words, the more water vapor that is in the atmosphere – the more we are emitting other harmful GHG emissions into the atmosphere that contribute to global warming. This positive feedback can help us to better understand and observe how our current human activities are harming the planet.
Greenhouse Gas Effect – Water vapor contributes to the greenhouse effect, which is when heat gets trapped in the atmosphere as a result of other greenhouse gasses.

👉 Overall, water vapor doesn’t have a set GWP in the way other greenhouse gasses do – but it can amplify the effect of other greenhouse gasses in the atmosphere, making it important in terms of reducing the negative impact of the greenhouse effect.

How can we reduce the amount of water vapor in the atmosphere?

Drying out the atmosphere from excess water vapor would be one effective way to reduce global warming, as water vapor exacerbates the greenhouse effect.

💡One idea to mitigate the amount of water vapor in the atmosphere would be to “freeze dry” the excess water vapor – which would be done by turning it into ice below the stratosphere where the air is the coldest.

“ At the highest altitudes before entering the stratosphere, the main process removing water vapor is the formation of ice that falls to lower altitudes." – Joshua Schwarz, research physicist at the National Oceanic and Atmospheric Administration (NOAA) Chemical Sciences Laboratory. ”

Here are a few other ways that we could reduce the amount of water vapor in the atmosphere:

Injecting Ice-Nucleating Participles (INP) – Think of when you’re putting ice cubes into your drink to make it colder. The same concept goes for ice-nucleating particles, or INP – which could be injected into the stratosphere to help reduce the temperature of water vapor and prevent it from provoking other greenhouse gasses.
Reduce Carbon Dioxide (CO2) Emissions – Although INP would have the same impact as a cooling effect, it is also imperative that we work as a human species to reduce the amount of carbon dioxide emissions we release into the atmosphere. This can help reduce the negative effects water vapor has on other greenhouse gasses.
Improving Forest Management – Vegetation releases water vapor via transpiration, meaning that it’s important to help protect our forest lands to ensure a stable water cycle and prevent too much transportation that could result in excess water vapor.
Reducing Urban Heat Islands – Dense cities with tall buildings and lots of concrete will often have increased water vapor as there’s no place for the excess water to be absorbed (think New York City). The best solution for this would be to implement the use of green roofs to improve urban vegetation and reduce local water vapor levels.
Boosting Soil Health – Climate smart farming can help to improve soil health and in turn, improve water retention and avoid high water surface evaporation rates.

Overall, water vapor is indeed a greenhouse gas – but it acts more as an indicator to how many other greenhouse gasses are currently in the atmosphere and exacerbates the greenhouse gas effect.

There are currently several ways to reduce the amount of water vapor in the atmosphere, but the most effective way to prevent water vapor from impacting our planet is to make an effort to reduce all other greenhouse gas emissions along the way.

What About Greenly?

If reading this article about water vapor and greenhouse gasses has made you interested in reducing your carbon emissions to further fight against climate change – Greenly can help you!

It can be overwhelming to figure out how climate policies could have an impact on your business, but don’t worry – Greenly is here to help. Click here to schedule a demo to see how Greenly can help you find ways to ensure your company is complying with all current and future environmental regulations.

Greenly can help you make an environmental change for the better, starting with a carbon footprint assessment to know how much carbon emissions your company produces.

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