The reason for the discrepancy is simple. The author of the study − which also includes emissions of another gas, ethane − says it is the first to take into account different production management systems and geological conditions around the world.
Lena Höglund-Isaksson, senior research scholar at the International Institute for Applied Systems Analysis (IIASA) in Laxenburg, Austria, describes the old figures, which were based on arguing that what happened in North American oilfields applied equally to the rest of the world, as “rather simplistic”.
The IIASA study, published in Environmental Research Letters journal, is another reminder that climate science – like all science – is only as dependable as the data on which it relies.
In a system as complex as the atmosphere, faulty data can have far-reaching consequences.
Potent greenhouse gas
Methane is a potent greenhouse gas − the most important contributor to climate change after carbon dioxide. There is now international agreement that methane is 34 times more potent than CO2 over a century, but 84 times more over a much shorter timespan – just 20 years.
Yet while methane concentrations in the atmosphere can easily be measured, it is much harder to establish how much the different sources, whether human or natural, contribute to the total. This information is needed to work out how to reduce emissions.
Dr Höglund-Isaksson explains: “In an oil reservoir, there is a layer of gas above the oil that has a methane content of 50% to 85%. When you pump the oil to the surface, this associated gas will also escape.”
In oil production in North America, she says, almost all of this gas is recovered, and most of the small amount that is not will be flared to prevent leakage − and possible explosions. A very small amount is simply vented.
In other parts of the world, where gas recovery rates are lower, much larger quantities of methane emissions are released into the atmosphere.
Read more at Oil’s Methane Emissions Higher than Feared
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