Reservoirs and Methane: Facts and Fears


A previous post explained how methane has been hyped in support of climate alarmism/activism. Now we have an additional campaign to disparage hydropower because of methane emissions from dam reservoirs. File this under “They have no shame.”

Here’s a recent example of the claim from Asia Times Global hydropower boom will add to climate change

The study, published in BioScience, looked at the carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emitted from 267 reservoirs across six continents. In total, the reservoirs studied have a surface area of more than 77,287 square kilometers (29,841 square miles). That’s equivalent to about a quarter of the surface area of all reservoirs in the world, which together cover 305,723 sq km – roughly the combined size of the United Kingdom and Ireland.

“The new study confirms that reservoirs are major emitters of methane, a particularly aggressive greenhouse gas,” said Kate Horner, Executive Director of International Rivers, adding that hydropower dams “can no longer be considered a clean and green source of electricity.”

In fact, methane’s effect is 86 times greater than that of CO2 when considered on this two-decade timescale. Importantly, the study found that methane is responsible for 90% of the global warming impact of reservoir emissions over 20 years.

Alarmists are Wrong about Hydropower

Now CH4 is proclaimed the primary culprit held against hydropower. As usual, there is a kernel of truth buried beneath this obsessive campaign: Flooding of biomass does result in decomposition accompanied by some release of CH4 and CO2. From HydroQuebec:  Greenhouse gas emissions and reservoirs

Impoundment of hydroelectric reservoirs induces decomposition of a small fraction of the flooded biomass (forests, peatlands and other soil types) and an increase in the aquatic wildlife and vegetation in the reservoir.

The result is higher greenhouse gas (GHG) emissions after impoundment, mainly CO2 (carbon dioxide) and a small amount of CH4 (methane).

However, these emissions are temporary and peak two to four years after the reservoir is filled.

During the ensuing decade, CO2 emissions gradually diminish and return to the levels given off by neighboring lakes and rivers.

Hydropower generation, on average, emits 50 times less GHGs than a natural gas generating station and about 70 times less than a coal-fired generating station.

The Facts about Tropical Reservoirs

Activists estimate Methane emissions from dams and reservoirs across the planet, including hydropower, are estimated to be significantly larger than previously thought, approximately equal to 1 gigaton per year.

Activists also claim that dams in boreal regions like Quebec are not the problem, but tropical reservoirs are a big threat to the climate. Contradicting that is an intensive study of Brazilian dams and reservoirs, Greenhouse Gas Emissions from Reservoirs: Studying the Issue in Brazil

The Itaipu Dam is a hydroelectric dam on the Paraná River located on the border between Brazil and Paraguay. The name “Itaipu” was taken from an isle that existed near the construction site. In the Guarani language, Itaipu means “the sound of a stone”. The American composer Philip Glass has also written a symphonic cantata named Itaipu, in honour of the structure.

Five Conclusions from Studying Brazilian Reservoirs

1) The budget approach is essential for a proper grasp of the processes going on in reservoirs. This approach involves taking into account the ways in which the system exchanged GHGs with the atmosphere before the reservoir was flooded. Older studies measured only the emissions of GHG from the reservoir surface or, more recently, from downstream de-gassing. But without the measurement of the inputs of carbon to the system, no conclusions can be drawn from surface measurements alone.

2) When you consider the total budgets, most reservoirs acted as sinks of carbon in the short run (our measurements covered one year in each reservoir). In other words, they received more carbon than they exported to the atmosphere and to downstream.

3) Smaller reservoirs are more efficient as carbon traps than the larger ones.

4) As for the GHG impact, in order to determine it, we should add the methane (CH4) emissions to the fraction of carbon dioxide (CO2) emissions which comes from the flooded biomass and organic carbon in the flooded (terrestrial) soil. The other CO2 emissions, arising from the respiration of aquatic organisms or from the decomposition of terrestrial detritus that flows into the reservoir (including domestic sewage), are not impacts of the reservoir. From this sum, we should deduct the amount of carbon that is stored in the sediment and which will be kept there for at least the life of the reservoir (usually more than 80 years). This “stored carbon” ranges from as little as 2 percent of the total carbon output to more than 25 percent, depending on the reservoirs.

5) When we assess the GHG impacts following the guidelines just described, all of FURNAS’s reservoirs have lower emissions than the cleanest European oil plant. The worst case – Manso, which was sampled only three years after the impoundment, and therefore in a time in which the contribution from the flooded biomass was still very significant – emitted about half as much carbon dioxide equivalents (CO2 eq) as the average oil plant from the United States (CO2 eq is a metric measure used to compare the emissions from various greenhouse gases based upon their global warming potential, GWP. CO2 eq for a gas is derived by multiplying the tons of the gas by the associated GWP.) We also observed a very good correlation between GHG emissions and the age of the reservoirs. The reservoirs older than 30 years had negligible emissions, and some of them had a net absorption of CO2eq.

Keeping Methane in Perspective

Over the last 30 years, CH4 in the atmosphere increased from 1.6 ppm to 1.8 ppm, compared to CO2, presently at 400 ppm. So all the dam building over 3 decades, along with all other land use was part of a miniscule increase of a microscopic gas, 200 times smaller than the trace gas, CO2.


Background Facts on Methane and Climate Change

The US Senate is considering an act to repeal with prejudice an Obama anti-methane regulation. The story from activist source Climate Central is
Senate Mulls ‘Kill Switch’ for Obama Methane Rule

The U.S. Senate is expected to vote soon on whether to use the Congressional Review Act to kill an Obama administration climate regulation that cuts methane emissions from oil and gas wells on federal land. The rule was designed to reduce oil and gas wells’ contribution to climate change and to stop energy companies from wasting natural gas.

The Congressional Review Act is rarely invoked. It was used this month to reverse a regulation for the first time in 16 years and it’s a particularly lethal way to kill a regulation as it would take an act of Congress to approve a similar regulation. Federal agencies cannot propose similar regulations on their own.

The Claim Against Methane

Now some Republican senators are hesitant to take this step because of claims like this one in the article:

Methane is 86 times more potent as a greenhouse gas than carbon dioxide over a period of 20 years and is a significant contributor to climate change. It warms the climate much more than other greenhouse gases over a period of decades before eventually losing its potency. Atmospheric carbon dioxide remains a potent greenhouse gas for thousands of years.

Essentially the journalist is saying: As afraid as you are about CO2, you should be 86 times more afraid of methane. Which also means, if CO2 is not a warming problem, your fear of methane is 86 times zero. The thousands of years claim is also bogus, but that is beside the point of this post, which is Methane.

IPCC Methane Scare

The article helpfully provides a link referring to Chapter 8 of IPCC AR5 report by Working Group 1 Anthropogenic and Natural Radiative Forcing.

The document is full of sophistry and creative accounting in order to produce as scary a number as possible. Table 8.7 provides the number for CH4 potency of 86 times that of CO2.  They note they were able to increase the Global Warming Potential (GWP) of CH4 by 20% over the estimate in AR4. The increase comes from adding in more indirect effects and feedbacks, as well as from increased concentration in the atmosphere.

In the details are some qualifying notes like these:

Uncertainties related to the climate–carbon feedback are large, comparable in magnitude to the strength of the feedback for a single gas.

For CH4 GWP we estimate an uncertainty of ±30% and ±40% for 20- and 100-year time horizons, respectively (for 5 to 95% uncertainty range).

Methane Facts from the Real World
From Sea Friends (here):

Methane is natural gas CH4 which burns cleanly to carbon dioxide and water. Methane is eagerly sought after as fuel for electric power plants because of its ease of transport and because it produces the least carbon dioxide for the most power. Also cars can be powered with compressed natural gas (CNG) for short distances.

In many countries CNG has been widely distributed as the main home heating fuel. As a consequence, methane has leaked to the atmosphere in large quantities, now firmly controlled. Grazing animals also produce methane in their complicated stomachs and methane escapes from rice paddies and peat bogs like the Siberian permafrost.

It is thought that methane is a very potent greenhouse gas because it absorbs some infrared wavelengths 7 times more effectively than CO2, molecule for molecule, and by weight even 20 times. As we have seen previously, this also means that within a distance of metres, its effect has saturated, and further transmission of heat occurs by convection and conduction rather than by radiation.

Note that when H20 is present in the lower troposphere, there are few photons left for CH4 to absorb:

Even if the IPCC radiative greenhouse theory were true, methane occurs only in minute quantities in air, 1.8ppm versus CO2 of 390ppm. By weight, CH4 is only 5.24Gt versus CO2 3140Gt (on this assumption). If it truly were twenty times more potent, it would amount to an equivalent of 105Gt CO2 or one thirtieth that of CO2. A doubling in methane would thus have no noticeable effect on world temperature.

However, the factor of 20 is entirely misleading because absorption is proportional to the number of molecules (=volume), so the factor of 7 (7.3) is correct and 20 is wrong. With this in mind, the perceived threat from methane becomes even less.

Further still, methane has been rising from 1.6ppm to 1.8ppm in 30 years (1980-2010), assuming that it has not stopped rising, this amounts to a doubling in 2-3 centuries. In other words, methane can never have any measurable effect on temperature, even if the IPCC radiative cooling theory were right.

Because only a small fraction in the rise of methane in air can be attributed to farm animals, it is ludicrous to worry about this aspect or to try to farm with smaller emissions of methane, or to tax it or to trade credits.

The fact that methane in air has been leveling off in the past two decades, even though we do not know why, implies that it plays absolutely no role as a greenhouse gas.

More information at THE METHANE MISCONCEPTIONS by Dr Wilson Flood (UK) here


Natural Gas (75% methane) burns the cleanest with the least CO2 for the energy produced.

Leakage of methane is already addressed by efficiency improvements for its economic recovery, and will apparently be subject to even more regulations.

The atmosphere is a methane sink where the compound is oxidized through a series of reactions producing 1 CO2 and 2H20 after a few years.

GWP (Global Warming Potential) is CO2 equivalent heat trapping based on laboratory, not real world effects.

Any IR absorption by methane is limited by H2O absorbing in the same low energy LW bands.

There is no danger this century from natural or man-made methane emissions.


Senators and the public are being bamboozled by opaque scientific bafflegab. The plain truth is much different. The atmosphere is a methane sink in which CH4 is oxidized in the first few meters. The amount of CH4 available in the air is miniscule, even compared to the trace gas CO2, and it is not accelerating. Methane is the obvious choice to signal virtue on the climate issue since governmental actions will not make a bit of difference anyway, except perhaps to do some economic harm.

Give a daisy a break (h/t Derek here)

Daisy methane


For a more thorough and realistic description of atmospheric warming see:

Fearless Physics from Dr. Salby


One comment

  1. craigm350 · February 27

    Reblogged this on WeatherAction News and commented:
    Something else not to worry about


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s