What is a Global Warming Potential?

Essentially, Global Warming Potential (GWP) is a common measurement tool that analysts use to compare different greenhouse gasses (GHGs) and identify emissions reduction opportunities. More scientifically speaking, GWP is a measure of how much energy the emissions of 1 ton of gas will absorb over a given period of time. 

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Want a memory trick? Everything you need to know is right in the name! AKA – How much potential does a gas have to warm our global atmosphere?

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Why are GWPs useful?

First things first, not all GHGs being emitted are the same, meaning they differ from one another in their ability to absorb heat and how long they stay in the atmosphere. When we understand how “effective” a certain gas is at absorbing heat, we can better understand its potential to warm our planet at large (aka contribute to climate change). 

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How do I interpret GWP?

Here are two key things to remember when interpreting GWPs.

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1: Carbon dioxide (CO₂) is the baseline.

CO₂, by definition, has a GWP of 1 because it is the gas being used as the reference point for all other GHGs. The amount of heat 1 ton of an emitted GHG can absorb is always compared to the emissions of 1 ton of CO₂. Analysts converting GHGs into CO₂ equivalents is like bakers converting 16 cups of milk into 1 gallon.

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2: GHGs have different lifespans.

GWP is not only specific to each GHG, but also specific to a time period. The most common time period used in measurements is 100 years, but alternative time periods are sometimes used so that analysts can understand gasses with shorter lifespans. Some GHGs, like methane, are better understood over a 20-year time period. The larger the GWP, the more a given gas warms the Earth compared to CO₂ over that same time period. 

Let’s look at an example: Methane (CH₄) is estimated to have a GWP of 27-30 over 100 years, compared to CO₂’s GWP of 1. You may be aware that CH₄ is a more potent GHG that absorbs more energy (aka heat) than CO₂, but it also stays in the atmosphere for a much shorter time (about 12 years as opposed to hundreds). GWP helps account for these differences. How? Well, let’s continue this example and switch up the time period… CH₄ is estimated to have a GWP of 81–83 over 20 years, which is clearly much higher than its GWP over 100 years.

Because all GWPs are calculated relative to CO₂, gasses with shorter lifespans than that of CO₂ will have larger GWPs while GHGs with longer lifetimes than CO₂ would, hypothetically, have smaller GWPs. When looking at GWP, it’s important to keep these numbers in context by understanding the timeline used!

How Does Finch Use GWP? 

GWP is an accepted unit of measurement within the scientific community and recognized on a, well, global scale. We’ll reference peer-reviewed GWP when it helps us understand the climate impact that a product has as a result of the various gasses it emits over the course of its lifecycle.

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Finch scores products on six different environmental footprints: climate, water, human well-being, ecological, waste, and raw materials. The climate footprint specifically looks at the GHGs, including carbon dioxide and methane, that are directly or indirectly released into the atmosphere by a product when it is made or used, and then we factor their respective GWP into a product’s resulting score.

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