French study warns of risks of downplaying role of methane in climate change


A new study in this month’s La Recherche alerts policy makers to the dangers posed by the current method of calculating greenhouse gas emissions which significantly downplays the role of methane in climate change scenarios.

The study, conducted by three climate and energy specialists, points out that reducing the bulk of methane emissions in France generated by rotting garbage dumps would have exactly the same impact on global warming as a 25-year campaign to insulate old buildings at the rate of 400,000 buildings a year.

Methane, or CH4, is produced by humid zones, coal extraction, the petrol and natural gas industry, cows and rotting organic matter. It is just one of the greenhouse gases that contribute to the greenhouse warming effect. Climate change modeling relies on a basic simplification whereby the effects of the other gases are calculated in terms of their carbon equivalent.

This equivalent measure is shorthand for the effect of the entire mix of gases. To attain the carbon emissions targets set by the IPCC, it is not enough to just cut our emissions of carbon dioxide but requires a concerted effort on the other gases as well.

This is a crucial distinction when it comes to translating the scientific recommendations into policy. For example, the final document from last year’s Grenelle on the Environment failed to mention methane in the policy conclusions on climate change.

The IPCC defines Global Warming Potential (GWP) as being a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to the same mass of carbon dioxide.

The GWP of methane can vary widely depending on the time frame in question. Methane only stays in the atmosphere for 12 years, which is short compared to carbon dioxide. As the life span of methane in the atmosphere is much shorter than that of CO2, its impact on climate change is greater over a shorter time period.

The European Union is committed to reducing its greenhouse gas emissions by 50 percent against the level of emissions in 1990. Over this period, the GWP of methane increases from the standard factor of 21 to 49. In five years, a ton of methane released into the atmosphere contributes as much as 101 tons of CO2 would to the greenhouse effect.

The study points out that cutting use of fossil fuels is not the only way to fight climate change because levels of methane in the atmosphere could increase sharply in the event of a big meltdown in the Arctic regions.

via La Recherche and Le Figaro


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