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Short-lived climate forcers

Efforts to mitigate the risks of climate change have primarily focused on reducing emissions of carbon dioxide. Recent work has broadened this focus to reconsider the role of other forcing agents in changing the climate, particularly short-lived climate forcers (SLCFs), which include methane and black carbon. SLCFs have drawn the attention of researchers, governments, and industry as part of a broader mitigation strategy. Overall, these climate forcers may have a significant effect, even though their emissions rates are smaller and atmospheric lifetimes shorter than carbon dioxide.

IPIECA held a workshop on SLCFs in October 2013, to investigate the science, sources, and understanding of current initiatives around SCLFs and the role and response of the oil and gas industry. The findings from the workshop will be condensed into a report which will be available in March 2014. A number of key messages were identified:

  • CO2 remains the predominant focus for long term climate mitigation, though global emissions of methane and black carbon can have important, and different, effects on climate. Because of their shorter atmospheric lifetimes and greater potency, short-lived climate forcers (SLCFs) offer opportunities for emissions reductions to have a greater impact on reducing warming than CO2 in the near term. Key uncertainties in determining the mitigation potential of SLCFs remain, including sources and quantities of methane and black carbon emissions, and the combined radiative forcing effects of black carbon and co-emitted species.
  • Various methodologies to estimate the contribution from the oil and gas industry to global methane emissions exist and each has its own uncertainty and inconsistencies with the other methods. Different approaches are important in triangulating the correct amounts, however estimates from these methodologies vary widely and work to reconcile these estimates remains. Future improvements in estimates of aggregated methane emissions, along with direct measurements from natural gas systems to estimate emission factors, will lead to further agreement and more accurate estimates overall.
  • Recent improvements in data collection efforts (e.g. UT/EDF study , US EPA GHG Reporting Program) have provided a wealth of reliable information that quantitatively characterizes some sources of methane emissions from the oil and gas supply chain. Results have shown significant variations from emission factors and activity levels used in national emissions inventories and other estimates of emissions from the oil and gas sector.
  • Emerging data suggests that methane emissions from oil and gas production in the US are on the order of 0.5% of total production, which is much lower than some estimates. This data also shows that conventional versus unconventional gas production do not have materially different methane emissions. As most existing methane estimates are based on data/studies from North America where “dispersed” oil and gas production with higher potential for methane emissions is standard, there is a need for more research beyond this region where many of the US sources do not exist and lower methane emissions are expected.
  • Measurements of methane emissions from natural gas production are also consistent with estimates that the life-cycle greenhouse gas emissions from electric power generation are roughly half for natural gas in comparison to coal per unit of electricity generated.
  • Global estimates of black carbon emissions from all sources, as well as the climate effects of BC and co-emitted species, continue to have substantial uncertainty. Emissions estimates may be underestimated, particularly with respect to developing nations where the majority of emissions originate. Open biomass burning (wildfires and agricultural burning) is the largest source of BC emissions (roughly 1/3 of global total), followed by residential solid fuel (biomass and coal) (~1/3), diesel engines (~1/6), and industrial sources (coal use, flaring, etc.) (~1/6).
  • Black carbon emissions from diesel engines continue to decrease in the developed world due to policies underway or implemented. Coincident improvements in engine technology and fuel quality can lead to significant improvements in emissions in countries with few other emissions policies. Marine shipping is estimated to be a rather small contribution to both global and Arctic black carbon emissions.
  • Black carbon emissions from upstream flaring are highly uncertain and vary significantly between flare types and gas compositions. Improved knowledge of black carbon formation in various flare operating conditions could lead to targeted and effective pathways for reducing emissions from high emitters.
  • Continued attention to acquiring better data, sharing of best practices, and mitigation efforts from the oil and gas industry will likely lead to further improvements in the oil and gas industry’s emissions management for both methane and black carbon. Organizations (e.g. IPIECA) and initiatives (e.g. Natural Gas Star, GGFR) provide important platforms for achieving improvements in emissions mitigation. However, opportunity costs, safety, and reliability must be factored in when considering mitigation options, and there is likely no single fit-for-purpose mitigation strategy.