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Tuesday, April 26, 2011

Sam Carana: Runaway Global Warming

Runaway Global Warming

by Sam Carana, Geoengineering, April 15, 2011
The East Siberian Arctic Shelf (ESAS) is a 2,000,000 km2 region that, due to polar amplification of global warming, can now be 10 °C (18 °F) warmer than average temperatures were 1951-1980 (NASA image below). 

Shakhova and Semiletov (2010) conclude that this ESAS region should be considered the most potential in terms of possible climate change caused by abrupt release of methane. 

They estimate that ESAS already releases some 3.5Gt of methane annually, adding that this is enough to trigger abrupt climate change.

How does this methane release compare to carbon dioxide? 

Concentrations of atmospheric carbon dioxide rose from 288 ppmv in 1850 to 369.5 ppmv in 2000, for an increase of 81.5 ppmv, or 174 PgC over 150 years.

By March 2011, the level of carbon dioxide was 392.4 ppmv. So, 104.4 ppmv of carbon dioxide was added by people since the start of the industrial revolution. 

If this was a one-time release, this 3.5 Gt (or Pg) of methane could have a greenhouse effect more than twice as strong as all the carbon dioxide that was added between 1850 and 2000, due to methane's high global warming potential (§1). However, methane is now released in such quantities annually in the ESAS region, while local concentration of methane (§2) and hydroxyl depletion (§3) make things even worse. 

1. Methane's high initial Global Warming Potential

In its first five years, methane is more than 100 times as potent as carbon dioxide as a greenhouse gas (image below, from a study by Dessus). At first, an annual addition of 3.5 Gt (or Pg) of methane would thus have an additional annual global warming impact equal to more than 350 Gt of carbon dioxide, or well over ten times people's annual global carbon dioxide emissions and more than twice as much as all the carbon dioxide emitted by people from the start of the industrial revolution till the year 2000, if all this methane was spread out over the globe.

2. Concentration of methane

All this methane is initially concentrated in ESAS, making things even worse. Earth's 510,072,000 km2 of surface is more than 255 times that of ESAS. While methane can spread out quickly, it will initially be concentrated in the ESAS region. A major methane release in the high Arctic would take 15-40 years to spread to the South Pole. This methane will allow less heat from sunlight in summer to escape into space, while the sun doesn't set. This could therefore cause summer temperatures to rise dramatically in the ESAS region, in turn causing further melting and more warming than we're already witnessing now. 

3. Hydroxyl depletion

To make matters even more catastrophic, high methane concentrations will result in an absence of enough hydroxyl to oxidize all this methane. A 2009 study by Drew Shindell found that increases in global methane emissions did cause a 26% hydroxyl decrease. Because of this, methane now persists longer in the atmosphere, before getting transformed into the less potent carbon dioxide. 
Above map, accompanying Shindell's 2009 study, does not show current ESAS methane emissions, which are literally off the chart, at levels of up to 1.85 ppmv.

Centre for Atmospheric Science study suggests that sea ice loss may amplify permafrost warming, with an ice-free Arctic featuring a decrease in hydroxyl of up to 60% and an increase of tropospheric ozone (another greenhouse gas) of up to 60% over the Arctic. This lack of hydroxyl means that methane will persist in the atmosphere for longer at its high global warming potency.

4. Hydrates and Runaway Global Warming

Such dramatic local warming is bound to trigger further melting of permafrost locally, resulting in further releases of methane. Massive amounts of methane are stored in the Arctic, much of it concentrated at high density in hydrates. One liter of hydrate can release up to 164 liters of methane. A rise in temperature could cause abrupt releases of huge amounts of methane from hydrates. 

Back in 2009, Katie Walter Antony warned that at least 50 Gt of methane will over time escape from lakes in Siberia alone (during the next decades to centuries). Schuur (2008) estimates the total amount of carbon stored in permafrost at 1672 Gt. Release of just a fraction of that in the form of methane would cause runaway global warming.  

5. What can be done about it?

Once runaway global warming starts, it feeds on itself. While dramatic reduction in global greenhouse gas emissions is imperative, that alone will not be able to stop runaway global warming.  

Geoengineering methods could reflect some of the sunlight in the Arctic back into space, such as by distributing sulfur dioxide into the stratoshphere by jets, cannons or hoses, or by enhancing cloud albedo as proposed by Stephen Salter and John Latham (see image left).

Even halving the amount of sunlight may not be enough to reduce warming in the region, if that would merely be like cutting methane's GWP in half. Moreover, it can take several years for warming to reach and penetrate hydrate sediments, as described by Nesbit, and once on its way, reducing surface temperature may not be able to reverse such as process quickly enough to avoid massive methane releases. In other words, the window of opportunity for solar reduction methods may already have closed.

Further methods include ways to ignite the methane using short, amplified and focused pulses of UV light from airplanes or satellites. UV light could also be used to produce more hydroxyl, in efforts to oxidize as much methane as possible.

Igniting or breaking down methane may also be possible using model airplanes, equipped with LiPo batteries and with solar thin film mounted both on top of and underneath the wings. Numerous such planes could navigate to the Arctic by autopilot in summer, when there are high concentrations of hydrogen peroxide and when the sun shines 24-hours a day. Flying figure-8 patterns with the wings under an angle could optimize capture of sunlight, keeping the planes in the air, while using surplus energy to power UV lights. Another methods could be to focus UV light on ozone and mix it with volatile hydrocarbons, in an effort to produce hydroxyls. At the end of summer, the planes could return home for a check-up and possible upgrade of the technology, to be launched again early summer the next year.

Such methods are further discussed at this geoengineering group.


Richard Pauli said...

Astounding summary. Thanks for posting.

Is it true that the IPCC climate models did NOT provide for methane?

Tenney Naumer said...

I think it very likely that the IPCC models did not include Siberian methane gun.

But you will find a clear discussion of it in James Hansen's book, near the end.