Global warming: Not all greenhouse gases behave the same way. Some linger for centuries; others hit hard and fade fast. Yet climate policy has long treated them as broadly comparable, using a single yardstick. A new study argues that this may be skewing carbon markets, and undervaluing some of the quickest ways to slow warming today.The study, published in the UK-based journal Environmental Research Letters, proposes a new framework called Radiative Forcing-based Accounting, or RFA, which aims to measure climate impact to better reflect how different gases warm the planet over time.The issue matters because the way emissions are counted affects how carbon credits are valued, which projects receive support, and how quickly climate benefits are delivered.Climate policy uses a common unit to compare different greenhouse gases. That unit is called carbon dioxide equivalent, or CO2e.Since carbon dioxide is the benchmark gas, other gases such as methane are converted into CO2e using a multiplier called Global Warming Potential, or GWP. For more than 30 years, the world has mostly used GWP100, which measures the warming impact of a gas over a 100-year period. Under this system, one tonne of methane is assigned a fixed CO2-equivalent value.How is this equivalent value calculated?To convert methane emissions into CO₂ equivalent (CO₂e), the amount of methane emitted (in tonnes) is multiplied by a factor called the Global Warming Potential over 100 years (GWP100). This factor represents how much warming methane causes compared with carbon dioxide over a 100-year period. For methane, this value is approximately 28, meaning methane has about 28 times the warming impact of CO₂ over 100 years.Also in Eplained | Expert Explains: Why India needs to work with its neighbours to improve air quality, status of efforts so farBy multiplying methane emissions by this factor (28), we express the emissions in CO₂-equivalent terms. More generally, converting methane to CO₂e requires applying a numerical multiplier that reflects methane’s warming potential relative to CO₂ over a chosen and comparable time period.Why is the 100-year rule being questioned?Story continues below this adBecause it does not reflect the timing of climate impact very well.Methane and carbon dioxide behave very differently in the atmosphere. Methane is powerful but short-lived. Carbon dioxide is less intense in the short run but lasts much longer. When methane is averaged over 100 years, much of its near-term impact gets diluted. That means a methane cut made today may look less valuable on paper than it is in the atmosphere.The criticism is that the present rule gives one fixed number for comparing gases whose warming patterns are very different.Why does methane need different treatment?Because cutting methane emissions is one of the fastest ways to slow warming in the near term.Story continues below this adIt stays in the atmosphere for about 12 years, but during that time it traps a great deal of heat. That means methane cuts can reduce warming sooner than many other climate actions. The proposal note also argues that present accounting tends to underestimate short-lived climate pollutants such as methane and black carbon.That is why the paper argues that the impact of methane mitigation should not simply be folded into a long 100-year average.What is the RFA framework proposed in the paper?Radiative forcing is a measure of how much a gas changes Earth’s energy balance. It’s the difference between incoming solar radiation and outgoing heat from Earth, and it already lies at the base of climate accounting and CO2e calculations.Instead of using one fixed multiplier, RFA looks at how strongly a gas traps heat and how long it stays in the atmosphere. In that sense, it tries to match carbon accounting more closely to the physical reality of warming over time.How is RFA different from the current method?The current method is static. RFA is dynamic.Story continues below this adUnder GWP100, methane gets one fixed value regardless of how long a project lasts. Under RFA, the value depends on timing, atmospheric lifetime, and the changing warming effect of the gas over the relevant period. GWP100 assumes constant radiative efficiency over a fixed horizon, while RFA tracks the time-dependent decay of warming impact over the gas’s actual atmospheric lifetime.That makes RFA more sensitive to near-term warming and to the timing of climate action.What does the paper mean by the “timing” of emission reductions?It means that cutting a tonne of methane today is not the same as cutting a tonne of methane many years later.Story continues below this adIf methane is reduced now, the atmosphere avoids that warming sooner. If the reduction is delayed, the warming happens first and the climate benefit arrives later. RFA is designed to capture that difference because it measures warming across the actual policy period rather than across an arbitrary 100-year window. Furthermore, RFA framework also accounts for a project’s own lifetime when calculating its mitigation impact in CO2e terms, further assuring that crediting is not averaged out across different interventions.That is one of the paper’s central points.How do the authors say RFA is more scientifically robust?The authors — four from the Institute for Governance and Sustainable Development and one from Cornell University — argue that greenhouse gases differ in two fundamental ways: radiative efficiency, which is the ability to absorb and emit energy, and atmospheric lifetime, which is how long a gas remains in the atmosphere.GWP100 simplifies those differences by averaging each gas’s effect over 100 years. RFA is presented as more physically grounded because it follows how warming changes over time as the gas decays in the atmosphere. The paper also links this approach to climate science summarised in recent IPCC assessments.Story continues below this adHow much of a difference does this new math make?A large enough difference to matter. The researchers applied the RFA framework to methane projects and found that the present accounting method under-credited them by about 36 to 40 per cent compared with the RFA approach. The authors have also created a dashboard to show the difference in credit generation under the two methods, though it adds that a practical validation study is still to be done.That means the paper is arguing that some projects may be delivering more climate benefit than present market rules recognise and should be financed accordingly.Which kinds of projects did the researchers look at?They looked at real-world methane mitigation projects that were credited under the Clean Development Mechanism or CDM (defined under the 1997 Kyoto Protocol). These included a landfill gas project in Guangzhou, a waste diversion project in Chandigarh, an industrial wastewater project in Tamil Nadu, and a livestock manure project in Brazil. These are all project types where methane can be captured or avoided.Story continues below this adThe point was to see how much current accounting might be missing in actual market settings.Why does this matter for carbon markets?Because carbon markets assign financial value to emissions reductions. The current system uses GWP100 as the characterisation factor to assess the climate value of a project. That factor is then used to calculate baseline emissions, project emissions, and the final quantity of credits generated. If the characterisation factor undervalues methane cuts, then projects that reduce methane may receive fewer credits than they deserve.Durwood Zaelke is founder and President of the Institute for Governance & Sustainable Development (IGSD). Zerin Osho is the Director of the India Program at IGSD.