Methane and GWP

How do we measure methane emissions and why does it matter?

The Paris Climate Accord measures methane emissions over a 100 year period, using what’s called the “100 year Global Warming Potential (GWP100), typically of 25. In other words “over 100 years, methane is 25 more warming to the planet than CO2.?

More recently, a number of prominent researchers and scientists have argued that this method is outdated, and potentially even dangerously understating the urgency of dealing with rising methane emissions. They have a point, we don’t really have 100 years to sort methane levels out!

Over the last 5 years in particular, there has been a shift towards using the GWP20 for Methane.

Why using the GWP20 over the GWP100 is so important

Increased Focus on Short-Term Climate Goals: The GWP20 reflects the increased urgency of climate action. Specifically. This shift reflects a growing recognition of the need to address short-lived climate pollutants (SLCPs) like methane to achieve near-term climate targets.

Scientific and Policy Discussions: Reports from bodies like the Intergovernmental Panel on Climate Change (IPCC) have increasingly acknowledged the importance of considering the GWP20 alongside the GWP100, particularly for methane, given its short-term impacts. The IPCC’s Sixth Assessment Report (2021) highlighted the critical role of methane in near-term warming, which sparked further discussion on the appropriate GWP metrics.

Advocacy for GWP20: Environmental advocacy groups and some climate scientists argue that GWP20 should be used more widely to reflect the urgency of methane reduction in the context of immediate climate action (see below). This has led to a gradual shift in some sectors towards favoring GWP20, particularly in regions or initiatives focused on rapid climate impact reductions.

To emphasize the urgent need for short-term climate action, several environmental advocacy groups and climate scientists have argued for the more widespread use of GWP20 for methane, including

Leading Environmental Advocacy Groups support GWP20

EDF (Environmental Defence Fund) has been a strong proponent of using GWP20 for methane. They argue that the traditional GWP100 metric understates the urgency of reducing methane emissions, given its significant short-term impact on global warming.

CCAC (Climate & Clean Air Coalition) is an international partnership that advocates for the reduction of SLCPs including methane. They recommend using GWP20 to highlight the immediate benefits of reducing methane emissions.

Carbon Tracker, a think tank focused on the impact of climate change on financial markets, has also advocated for a greater emphasis on GWP20. They argue that using GWP20 could better reflect the near-term risks associated with methane emissions.

Prominent Climate Scientists support GWP20

Drew Shindell, a climate scientist at Duke University and a leading author on methane research, has been vocal about the need to use GWP20 to more accurately reflect the short-term impact of methane.?

Durwood Zaelke, President of the Institute for Governance & Sustainable Development (IGSD), has advocated for using GWP20 in climate policies.

Robert Howarth, a professor of ecology and environmental biology at Cornell University, has argued for the use of GWP20 in the context of methane emissions from natural gas production. His work suggests that the short-term impact of methane is often underestimated when using GWP100.

Michael Oppenheimer, a climate scientist and professor at Princeton University, has also supported the use of GWP20 in discussions around methane, particularly in relation to policies aimed at achieving near-term climate goals.

Summary

Using the GWP20 for methane also impacts how carbon credits are calculated. UNEP chair Inger Anderson called reducing methane “Our strongest lever to reduce climate change in the next 25 years”, yet remarkably, only 2% of all climate finance is directed towards mitigation mitigation

Some commentators have even gone so far as to suggest that because methane is 150 times more warming for the 9-12 years it is in the atmosphere, this is the figure we should use.?

It has also been credibly postulated that even the old measurements will have to be revised upwards, because?

1. Wildfires cause particulates in the upper atmosphere that the methane-decomposing hydroxl molecules prefer over methane, leading to methane remaining in the atmosphere longer and longer
2. Decreased use of shipping bunker fuel has caused a decrease in SO2 in the atmosphere. While SO2 is a known pollutant that contributes to smog and respiratory illnesses, it is also an oxidizing agent for methane. Less SO2 means less methane being oxidized, leading to methane again remaining in the atmosphere longer
3. The sheer volume of methane in the atmosphere itself

Migrating to universal use of at least the GWP20 for methane would be a sensible starting point to properly assess and incentivize the important task of prioritizing methane reduction appropriately.?