Methane & Climate

Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills.

Methane Hydrate Clathrate
Ocean Methane Emissions

Methane (CH4) is emitted from a variety of both human-related (anthropogenic) and natural sources. Human-related activities include fossil fuel production, animal husbandry (enteric fermentation in livestock and manure management), rice cultivation, biomass burning, and waste management. These activities release significant quantities of methane to the atmosphere. It is estimated that more than 60 percent of global methane emissions are related to human-related activities (IPCC, 2007:a). Natural sources of methane include wetlands, gas hydrates, permafrost, termites, oceans, freshwater bodies, non-wetland soils, and other sources such as wildfires.

Source: EPA

Current Considerations

When one views the recent geologic past (one million years) and warming, one can see that even in warmer states there is no strong indication of methane release. In our last interglacial, we had warmer temperatures and higher sea level, but there is no indication of large scale methane clathrate release.

One can also look back to periods of extended warm periods and still see nothing like that of the PETM (Paleocene–Eocene Thermal Maximum) event, which is suspected to be a large scale release of methane from hydrate clathrates into the atmosphere.

Methane is released by various human activities and contributes to the excess load of greenhouse gases since the pre-industrial era.  The growth rate in the atmosphere stalled for a while, but appears to be rising again.  The reason for this is not fully understood.

  • One issue is how to reduce human-induced methane emissions in the future to slow the growth or (more hopefully) get its concentration to start to fall.
  • Another issue is whether global warming will trigger methane releases from natural reservoirs, thus feeding back to drive further warming.

Although methane has been widely implicated as a possible cause of past climate changes, I think the jury is still out as to whether it was ever a major cause.

Recent studies continue to examine methane and the picture is slowly coming into greater focus.

The main problem is that we don’t have any proxies before the ice-core era of past methane changes, and during the ice-core era, the methane changes were too small to be the main cause of the climate changes.  The fact that we can’t show that methane was a major driver of climate changes in the past doesn’t mean we don’t know its relative greenhouse effect.  This is established securely from the optical properties of the molecule.

There is increasing evidence that the major extinctions of the past several hundreds of millions of years are associated with long lived events following major tectonic disturbances that result in release of greenhouse gases, with associated global warming, ocean anoxia etc.

For example the early Jurassic extinction is associated with events (greenhouse gas induced warming) lasting 200,000 years. Likewise comprehensive analyses shows a coincidence of major tectonic events, and resulting elevation of greenhouse gas levels, are associated with several of the major extinctions of the last 300 million years. Note that CO2 isn’t the only player. Methane is implicated in several of these events (see especially the PETM below) and sulphurous oxides and their effects on ocean acidity and oxygen content are also implicated.

Greenhouse environments are associated with the very delayed (millions of years) recovery of biota following these extinctions.

The lesser extinction associated with the Paleo-Eocene-Thermal Maximum (PETM) 55 MYA is probably the best characterized (not surprisingly since it’s the most recent!) example of massive tectonic processes (the opening up of the N. Atlantic as the plates separated) associated with enhanced atmospheric greenhouse gases, ocean acidification etc.

And even the end-Cretaceous extinction (that did it for the dinosaurs) seems to have had at least a significant component from massive flood basalt events (that resulted in the Deccan Traps in what is now India). In fact there is increasing evidence that the impact that resulted in the Chicxulub crater in the Yucatan post-dates the onset of the extinction by several 100,000’s of years, and the extinction is associated with global warming (including a sudden contribution from the impact into limestone-rich deposits that vaporized massive amounts of carbonate (limestone) back into CO2).

Continued focus on these events and probable causes will likely reveal increasingly accurate understanding.

Links

Permian Mass Extinction

250 Million years ago, one of the largest earth extinction events took place. Scientists examined the event and some examined the possibility of a flood basalt eruption. where the earth crust opens and allows continual eruption. The theory was that this would release large amounts of CO2. However, when the amount of CO2 release was examined, it did not look like there was enough CO2 release to cause a 10 degree C temperature increase.

End-P

Geologic and fossil evidence of the Permian event known as End-P (The end of the Permian period).

Peter Ward – University of Washington

Since CO2 could only account for about 5 degress C of temperature increase.

Further examination of the geologic record revealed a large amount of 12C

Three distinct extinction events were seen in the paleo record. The first event began close to the eruption event and went on for about 40,000 years. At about 40-45k years there was a sharp extinction event in the ocean of nearly everything in the ocean. The third event went on to about 80k years after the eruption event began.

Analysis of the rock showed that after the marine extinction, but before the final death of everything on the land, there was an increase in Carbon 12. This is not normally produced by rotting plants or animal matter. It is however found in methane hydrates stored in what are known as clathrate traps.

The leading theory is that when the temperature reached about 4-5 degrees C of temperature increase, the methane released from the ocean.

links

2008

International Siberian Shelf Study 2008 (ISSS-08): The major IPY ship-based program along the entire Eurasian-Arcticcontinental shelf with combined biogeochemical and geophysical observations

Why should the East Siberian Shelf be considered a new focal point for methane studies in terms of Global ClimateChange?

Large Release of Methane Could Cause Abrupt and Catastrophic Climate Change as Happened 635 Million Years Ago, UCR-led Study Warns

Snowball Earth termination by destabilization of equatorial permafrost methane clathrate

2005

Dissolved Methane Anomalies Over the East-Siberian Arctic Shelf: Signs of Gas Hydrate Decay?

Methane hydrates and global warming

2004

Temperature sensitivity and time dependence of the global ocean clathrate reservoir

The Dynamics of permafrost and the Gas Hydrate Stability Zone in Rift Structures on the Shelf of the Seas of Eastern Eurasia

Methane: A Scientific Journey from Obscurity to Climate Super-Stardom

2003

Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis

Atmospheric composition, radiative forcing, and climate change as a consequence of a massive methane release from gas hydrates

Wikipedia

https://en.wikipedia.org/wiki/Clathrate_gun_hypothesis