What is Dual-Term Greenhouse Gas Accounting?

Less Meat Less Heat at COP23 – Our Agenda for Better Greenhouse Gas Accounting


Mark Pershin, founder of Less Meat Less Heat, will attend COP23 and lobby national delegations to revise greenhouse gas accounting.

COP23, the 23rd Conference of the Parties to the United Nations Framework Convention on Climate Change (UNFCCC), will take place on 6-17 November this year in Bonn, Germany. Mark is aiming to draw the participants’ attention to the role of agriculture in driving global warming and will lobby for bringing the emissions produced by the sector into the focus of climate policy debates by readjusting greenhouse gas accounting and specifically, by introducing dual GWP20+GWP100 reporting.   

UNFCCC uses particular metrics to quantify and compare the global warming effect of different greenhouse gases. Since the Kyoto Protocol (1997), the default metric adopted by UNFCCC, as well as most other international and national actors, has been the 100-year Global Warming Potential (GWP100). However, like any other metric, GWP100 is based on particular value judgements, which frame our understanding of climate change and eventually affect the course of global climate action.

GWP is a metric that compares the amount of warming caused by a greenhouse gas over a chosen period of time – usually 20, 100 or 500 years – with that of carbon dioxide (CO2). The selected time frame is arbitrary, but determines the estimated effect of different greenhouse gases depending on their lifespan. For example, GWP20 takes into account only a 20-year time frame ignoring later climate effects. Therefore, it is not appropriate for reporting the so-called long-lived gases that stay in the atmosphere for more than 20 years, such as CO2, which has a lifespan of 100-1,000 years.

On the other hand, when a longer time frames used (GWP100 and GWP500), GWP obscures the effects of short-lived climate pollutants, such as methane, fluorinated gases and black carbon. These pollutants stay in the atmosphere for shorter periods of time. Therefore when their warming effect is calculated, it is averaged over a period that is a few times longer than their lifespan, making them look much less significant than they actually are. For example, the GWP100 multiplier of methane is 34, meaning that it is estimated that over 100 years, one tonne of methane produces 34 times more warming than one tonne of CO2. However, methane only lasts in the atmosphere for around 10-12 years, hence by averaging out it’s warming over 100 years, we grossly underestimate it’s impact during those first 10-12 years.  If we were to use a 20 year time frame to measure the impact of methane on the climate, one tonne of methane would provide 86 times more warming than one tonne of CO2.

Given that GWP100 is the ‘gold standard’ of greenhouse gas accounting, its underreporting of the potency of short-lived climate pollutants is further reproduced in countries’ emissions inventories and, eventually, in national and international mitigation strategies. As a result, global climate action today is heavily skewed towards CO2 as the primary target, leaving short-lived climate pollutants out of the policy agenda.

CO2 is certainly the main driver of long-term warming and targeting it is vital if we aim to preserve a safe and healthy environment for future generations. However, if produced continuously, short-lived climate pollutants can also create a cumulative long-term warming effect, which is comparable to that of long-lived pollutants. In fact, 42% of current warming is due to short-lived pollutants. Further neglect of these agents can increase the risk of reaching a temperature overshoot and tipping points for runaway climate change. Conversely, addressing them alongside CO2 represents a powerful opportunity to create a more immediate impact, which cannot be achieved through CO2 reductions alone, even under very ambitious mitigation strategies. For example, it is predicted that cutting methane emissions by 46% would have the same effect by 2050 as ceasing CO2 emissions altogether. Moreover, actions targeting short-lived climate pollutants also tend to be linked to human health, development and sustainability benefits, and can also contribute to cutting costs of overall climate change mitigation.

But as a result of GWP100 centrism, these mitigation opportunities are predominantly overlooked. Currently, the need for action in the sectors which are the main sources of the short-lived climate pollutants for example, agriculture and associated activities such as pasture and stubble fires, deforestation and industrial livestock expansion is underplayed. Instead, climate mitigation debates primarily focus on the sectors which are the dominant sources of CO2 energy and transportation. But to achieve the goal set by the Paris Agreement, it is critical to have a diverse portfolio of climate change mitigation strategies covering all pollutants and all contributing sectors, which requires bringing short-lived climate pollutants into focus and updating the greenhouse gas accounting system.

The aim of Less Meat Less Heat at COP23 will be to convey the message that dual GWP20+GWP100 reporting will highlight more opportunities for climate action and will help avoid policy and ethical trade-offs between near-term and long-term objectives.

The technical details of the policy proposal can be found here and the policy FAQ is a good resource for any further questions. Put Climate On Pause is a growing coalition of non-profit organisations and country delegations to support the implementation of this goal at COP23 and beyond. Should your organisation wish to join our coalition then please contact us ASAP at mark@putclimateonpause.org

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