Current accounting system for methane emissions overestimates the warming potential of biogen methane significantly and should be amended to correctly reflect recent scientific progress.
Much has been said recently about “new science” changing the way we should think about how methane is assessed and its impact on climate change. To understand this, you must first have a basic understanding of what the scientists are trying to do.
Global warming is an obvious concern of science about what is happening in our atmosphere. This is a relatively new science, so it's unreasonable to expect any assumption to be 100% correct from the start. One of the assumptions behind global warming is that gases that retain more heat are becoming increasingly important in the atmosphere.
Er is veel gezegd over de rol van kooldioxide (CO2) in dit verband, aangezien dit het dominante gas is. Het wordt geproduceerd tijdens de ademhaling van de meeste levende wezens en wordt door fotosynthese uit de atmosfeer gehaald om de groei van planten te stimuleren. Maar het komt ook vrij bij het verbranden van fossiele brandstoffen, bomen en ander biologisch materiaal. Bovendien kan het worden geproduceerd door een reeks chemische reacties, zoals de productie van cement.
Methane (CH4) is a known greenhouse gas (GHG) in agriculture because of biogenic emissions from livestock. CH4 emissions also occur in the production and transport of coal, natural gas and oil. Methane is also emitted from the decay of organic waste in municipal solid waste landfills.
Nitrous oxide (N2O) is a much more potent greenhouse gas and originates mainly from human activities, such as agriculture, fuel combustion, wastewater management and other industrial processes. It is very powerful and lingers in the atmosphere for a long time.
Another important group are the fluorinated gases. These are very potent greenhouse gases, emitted mainly by industrial processes, with global warming 23,000 times higher than CO2.
Global warming potential;
Different gases have different characteristics that affect their impact on global warming.
The net impact depends on the individual gas;
- How much of each gas is present
- How long it is likely to have an effect before breaking down.
For years, scientists have used the 100-year global warming potential (GWP) of each gas to estimate its impact on atmospheric temperature.
In the first instance, it was assumed that all gases were stable and had an infinite lifespan. Gases with a higher GWP absorb more energy than gases with a lower GWP and thus contribute more to global warming.
Recent scientific developments;
Recent scientific developments have led scientists to question the GWP measure and many are now considering it as unrealistic for methane.
In a recent article by Professor Ray Bates of UCD, http://www.raybates.net/ titled New Scientific Developments Require a Change in Methane Accounting, the author explains that the science used in the current methane accounting system does not make the required distinction between situations in which methane emissions are increasing, stable or decreasing.
In all three situations, the GWP system assigns a CO2 equivalent for methane solely on the basis of the emissions in the current year. This implies a continued contribution of methane to global warming.
This is not realistic, as a declining trend in methane emissions could contribute to global cooling. This happens when the warming from methane emissions in previous decades decreases faster than the warming from new methane increases.
Prof Bates further explains that a revised methane assessment process or metric, called GWP Star (GWP*), was developed by researchers at the University of Oxford. The GWP* metric addresses this important shortcoming by incorporating the current year's methane emissions and the trend for the most recent 20-year period. Prof Bates agrees with Oxford group leader Prof Myles Allen who called the GWP "an outdated accounting system".
Prof Bates argues that when the GWP* measure is applied to Ireland's agricultural methane emissions, it indicates that they had a much smaller impact on global warming than the GWP measure suggests over the past 20 years. Indeed, GWP* indicates that our methane emissions have contributed to global cooling in recent years, having declined since the late 1990s.
Given these findings, Prof. Bates argues that Ireland would have appeared in a much more favorable light in the recent EU emissions tables if the new accounting system had been used.
Part 2 of this blog next week!
Leave a Reply