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Climate Time Horizons, Howarth, and Catastrophic Methane Release

Robert Howarth has been criticized by ANGA[1] (America’s Natural Gas Alliance) for using an unconventional time horizon[2] in his study “Methane and Greenhouse-Gas Footprint of Natural Gas from Shale Formations.”  While Howarth’s Paper is seriously flawed (the existing data on natural gas leakage rates is extremely limited[3]), a few pieces are worth salvaging from the flames.

The Intergovernmental Panel on Climate Change uses a baseline 100 year time horizon to measure the radiative forcing caused by gases in the atmosphere, while the Howarth paper uses 20.  MIT Energy Initiative ED Melanie Kenderdine went as far as to say “What he has done in his analysis is deviated from what are accepted standards, accepted by EPA, DOE, the IPCC, European Trading Scheme, California Air Resources Board, where essentially the denominator that they use to calculate the impacts of various greenhouse gases is an agreed upon hundred years; Professor Howarth uses 20 years.”  Kenderdine suggests that Howarth is setting up his GHG comparison outside the realm of scientifically accepted standards—similar to claiming statistical significance at a .20 alpha.

Kenderdine’s characterization is misleading.  While the IPCC does use the 100 year time frame, they also use 20 year, and 500 year periods.  They note that “the choice of the time horizon depends in part on whether the user wishes to emphasize shorter-term processes…or longer term processes that are linked to sustained alterations of the thermal budget.  In addition, if the speed of potential climate change is of greatest interest (rather than the eventual magnitude), then a focus on shorter time horizons can be useful.”[4]

What time frame is most relevant here?  The Howarth paper was clearly aimed at the natural gas industry, in the height of the shale boom.  The golden age of gas[5] is upon us.  If global use of natural gas expands at projected rates, emissions from gas production, transportation, processing, storage, and consumption will have a greater impact due to increased volumes.  The EPA’s recent CO2 rule will likely result in the majority of new power plants built in the US to run on natural gas.  Natural gas leaked into the atmosphere has a Global Warming Potential of 21  over the 100 year time horizon.[6]  Under the 100 year time horizon, it appears very likely that a switch to natural gas could result in a reduction of net radiative forcing over the century—however, the “net” may not be the optimal way to look at the situation.  In 100 years, the damage may well be done.  Consider the following:

1.)    Switching a short time frame GHG for a long time-frame GHG is essentially trading a steeper short term rise for an earlier slope downward.  Natural gas instead of coal, for example, would make short term temperature increases more severe, but long-term temperatures more stable.  This would be OK if ecosystems and economies were robust enough to take the rapid climb—however many impacts are related to seasonal temperature, not long-term averages.[7]

2.)    Feedback loops in the artic make short term changes to temperature more important.[8]  Short-term warming of the permafrost releases additional GHGs.  Sea ice formation is a central hub of the artic ecosystem, and depends to multiple factors, all of which have the potential to ‘snowball’ with near-term warming.  Previously sequestered methane in the artic will be increasingly released into the atmosphere, further increasing the rate of warming as well as extending the period of rapid increase in temperatures.[9]  The most potentially catastrophic example of this has to do with the release of the EIA’s favorite resource for tomorrow: Methane Hydrates.  Previous releases in the Paleocene resulted in 1-8 degree (C) rises in temperature, dependent on latitude.[10]  Methane Hydrates are currently stabilized along continental margins, and the exact amount of forcing that would trigger a release is unknown.[11]

Because climate stabilization must occur before the ‘tipping point,’  I would argue that short-time frames are essential in consideration of emissions.  How fortunate that policymakers operate in 1-4 year time horizons.


[3]  US Inventory of Greenhouse Gas Emissions and Sinks 1990/2007 (EPA, 2009)

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Combustible Ice in China as new energy source

What is Combustible Ice?  Combustible Ice is also known as Methane Gas Hydrate, or Methane Clathrate, or fire ice.  It is a clathrate compound which is formed from water molecules under high pressure and low temperatures.  These water molecules form an ice like cage that encapsulates a gas molecule, in this case, methane [1]."combustible ice"

China’s western Qinghai provincial governor Luo Huining said on March 6th 2010, that they will see increased explorations for the emerging “combustible ice” clean energy.   The Qinghai Porvince recently found in September 2009, that it is sitting on a quarter of the Qinghai-Tibet Plateau reserve.  This reserve is estimated to equal at least 35 billion tones of oil which could supply energy to China for the next 90 years [2].  China plans to spend $100 million in the next 10 years on research for Methane Hydrate.

The total resources for combustible ice were estimated to be twice as large as the total coal, oil and natural gas reserves in the world [3]. But according to a study done by BP exploration, the current Methane hydrate reserve is less than the total coal and oil reserve together, but more than the natural gas reserve [6].  According to a study done by USGS, it is an estimated more than 1,300 trillion cubic feet of methane gas is off of North and South Carolina coasts in the form of Methane hydrate [4].

combustible ice resource map

So what makes this combustible so special? Approximately one cubic meter of “combustible ice” equals 164 cubic meters of regular natural gas [2]. It is considered a cleaner energy because when burned, it only puts off water and CO2. It does not have any SOx or NOx emissions.  Since the gas is held in crystalline structure, it is a lot denser than typical methane gas.  Also, methane clathrates are stable at a higher temperature (−20 vs −162 °C) than LNG, there might be some interest in converting natural gas into clathrates rather than liquefying it when transporting.

But this “emerging energy source” can come at a cost.  Right now it is not economical to extract and too expensive, about 8 times compared to the natural gas in China today (1$ per cbm compared to 0,125 $ per cbm)[3].  The extraction and mining of the combustible ice can be environmental damaging as well.  When burned, it still would be releasing CO2 into the atmosphere which is not really solving the greenhouse gas situation.  If not handled properly, when brought to the surface, the methane escapes from the “ice” and if not burned goes into the atmosphere.  This is not good because methane is much more potent as a green house gas goes than CO2 and can cause more damage than CO2.  Then again look at nuclear energy, it has environmental harmful nuclear waste, but we use it as a clean energy today.  So with more research to be done, this CombustibleIce could be used as a source of energy in the near future.

[1] http://www.ornl.gov/info/reporter/no16/methane.htm

[2] http://news.xinhuanet.com/english2010/china/2010-03/06/c_13200033.htm

[3] http://www.leonardo-energy.org/drupal/node/901

[4] http://marine.usgs.gov/fact-sheets/gas-hydrates/title.html

[5] http://www.cctv.com/program/Nature&Science/20050620/102404.shtml

[6] http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V62-4BMTJ4G-1&_user=108429&_coverDate=08%2F31%2F2004&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000059713&_version=1&_urlVersion=0&_userid=108429&md5=4a34c5663c1680c34a753fdfcec4c5b4#toc5

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