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Methane and global warming

Updated: May 23



How much do methane emissions impact global warming? 


A lot of measurement, reduction, and offsetting vocabulary centres around carbon dioxide:  carbon footprints, CO2e, carbon offsetting, etc. So, if it’s all about carbon dioxide, do the other greenhouse gases (GHGs) matter, and do they need to be declared in your emissions reporting?


The short answer is, yes, they matter a lot - particularly methane in the short term. And yes, we do measure them. We’ll get into the long answer below, complete with all the key information you might need about methane and global warming. 


Before we get started, now is probably a good moment for a reminder of what CO2e is, since adding the ‘e’ completely changes the meaning.



CO2e: Carbon Dioxide Equivalent


When you see emissions in terms of CO2e, this doesn’t mean that that exact amount of carbon dioxide was released. CO2e refers to the global warming impact of the greenhouse gas(es) that was emitted. 


The reduction of 1 tonne of CO2e means the reduction of an amount of greenhouse gas that has the equivalent global warming potential as 1 tonne of CO2. The tonne amount of the gases varies depending on which gases are in the mix. 


CO2 emissions: carbon dioxide emitted.

CO2e emissions: total greenhouse gases emitted, in terms of carbon dioxide global warming impact equivalent. 


The IPCC lists the Global Warming Potentials (GWP) of each greenhouse gas over 100 years, which can be used to calculate the CO2e.



Methane (CH4)


Methane is made up of one carbon atom bonded to four hydrogen atoms (CH4). It is the main component of what we know as natural gas. It is an extremely potent greenhouse gas with a high Global Warming Potential (GWP), and a major contributor to rising global temperatures. 


The three largest sources of atmospheric methane


Methane is produced and released in many different ways, but these are the top sources:

  • Livestock. Livestock are the largest source of atmospheric methane, so that gas is one of the reasons a vegetarian or vegan diet is generally more environmentally friendly.

  • Oil and gas operations. Livestock might be in the lead, but this second source of atmospheric methane is close behind. This is the easiest spot to reduce methane emissions, since these industries have both the capital and the incentive: reducing methane leaks means more natural gas to sell, and a bigger profit margin.  

  • Waste management. Methane is produced when organic waste decays under anaerobic conditions, so waste management is also an important source to look at. 


What is methane’s Global Warming Potential (GWP)?


Methane’s GWP is 28-36, so you can calculate methane’s CO2e by multiplying the tonnes of methane by a number in this range. The exact number would depend on which methodology you’re using. 


What complicates things a bit, is that the standard GWP measurement is GWP100 which looks at the impact over 100 years. If you look at a shorter period, methane’s GWP would be much higher. Discover more on that below.


Does CH4 contribute to global warming?


Yes, according to UNEP, methane is responsible for roughly 30% of global warming since pre-industrial times.


Which is more harmful, methane or CO2?


It’s all relative. Methane molecules trap more heat than CO2, but its lifespan is much shorter.


Over a 20 year time period, its GWP is 84-87 times higher than carbon dioxide. So, while CO2 is more harmful in the long term, the near time impact of reducing methane emissions is significant. 



Methane reduction to meet global climate goals


Global goals of staying below 1.5 degrees of warming since pre-industrial levels are proving challenging. We need some near-term solutions to help buy time as longer term plans like transitioning away from fossil fuels are put into place. Since methane’s impact is so large in the first 10 years after release, reducing it is a quick win. 


This doesn’t mean we should focus all energy on methane over carbon dioxide, but rather, by focusing on both, we might be able to make up for extended transition timelines that are putting 1.5 degrees at risk. 



What GHG is the biggest contributor to global warming?


CO2 is the biggest contributor to global warming, with methane in second place. Here you can see a breakdown of how gases contribute to global warming, calculated using the GWP of each gas over 100 years (GWP100).


Breakdown of total GHG emissions. CO2 - 75%, CH4 -18%, N2O - 4%, fluorinated gases - 2%.
Source: French ministry of energy transition, 2023

Which GHGs should businesses include in their emissions reporting?


Carbon accounting could also be called GHG accounting since all those gases are considered in the measure, reduce and offset process. A business footprint includes all GHG contributors over a certain trace level. All GHGs will be converted to CO2e for reporting, based on GWP100. 


If you’re unsure how to get started on carbon accounting or reporting, our team of experts are available to help at any stage of the process. Book in a time to chat today, free of charge, no commitment required or see more about our services here


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