As the world hit a new and ominous CO2 record of 400 parts per million and rising, just one milestone on the road toward ever greater harm from damage via human-caused greenhouse gas emissions, another record was quietly reached. At the Mauna Loa Observatory, world-wide methane levels hit a new record average of 1830 parts per billion in April of 2013 even as they continued to ramp higher.
(Image source: NOAA ESRL)
The new record follows a short-term rise in atmospheric methane that began in 2007 and has continued to this day. It also caps a long-term rise in methane that began at the start of the industrial revolution and, through a long ramp-up, has resulted in atmospheric methane levels rising from about 750 parts per billion to the record high level of 1830 parts per billion today.
You can view this long-term rise in atmospheric methane in the second chart, provided by NASA, below. Note that atmospheric levels given are only updated through 2008, just at the start of the most recent jump in atmospheric methane concentrations:
(Image source: NASA)
This ramping up of atmospheric methane that began in 1750 and has continued to this day has, so far, been mostly caused by humans. Primary sources for human methane emissions include landfills, coal mining, leaks from oil and gas infrastructure, and the digestive generation of methane in the guts of livestock animals such as cattle. An explosion in the volume of methane coming from these sources pushed world methane levels about 1080 parts per billion higher over the last 250 years.
This increase has had a powerful impact on global warming caused by humans. It is estimated that, at current concentrations, methane’s contribution to global warming is about 28% that of CO2. The reason for this, even though atmospheric levels for methane are more than 200 times lower than CO2, is that methane is at least 25 times as potent a heat absorber by volume (and as much as 105 times during the short term). What this means is that atmospheric methane increases are a huge contributor to climate change.
Now, I want to stop here before going any further. And the reason is that some oil industry cheer leaders have made the false argument that reducing human methane emissions is more important to mitigating the impact of climate change than reducing CO2 levels. The short answer to this false claim is that they’re both important and there’s no way to address human climate change without reducing both CO2 and methane emissions. And, since there’s at least 500 parts per million worth of CO2 in the remaining fossil fuel reserves, for us to maintain much hope of a livable future climate will necessitate that most of these fuels remain unburned or that the carbon from these fuels is captured and permanently sequestered.
Human-caused warming results in increasing methane release from Earth’s environment
Unfortunately, humans are no longer the only contributor to rising levels of atmospheric methane. New research being conducted by NSIDC, NASA, and a number of scientists around the world show that organic material stored in the world’s permafrost and methane clathrates at the bottom of the ocean are showing signs of stirring.
Permafrost is a region of frozen soil that dominates large sections of the Northern Hemisphere and the entire continent of Antarctica. This image, provided as part of NASA’s CARVE research project, shows the Northern Hemisphere’s permafrost zones.
(Image source: NASA)
As humans have driven the climate to warm, larger and larger sections of the northern permafrost have been subject to thaw. As the permafrost thaws, it opens organic material, sequestered for tens of thousands of years, to decay. If the region where the permafrost melts is predominantly wet, the organic material breaks down into methane. If the region is primarily dry, carbon dioxide is produced.
The volume of organic material locked in permafrost is massive. In fact, NSIDC shows that there are about 1,400 gigatons of carbon locked up in the world’s permafrost. This is nearly twice the volume of all the carbon currently contained in the atmosphere. For even a small fraction of this carbon to be released via human warming would have dramatic consequences. And, since many regions in the Arctic are predominantly wet, a large portion of any future release is likely to be methane.
Already, research is beginning to indicate that carbon stores in the Arctic are being set free by human-caused warming. In NASA’s most recent press release describing its CARVE research mission, entitled “Is a Sleeping Giant Stirring in the Arctic,” NASA scientists were said to have found large methane emission sources comparable to major cities.
“Some of the methane and carbon dioxide concentrations we’ve measured have been large, and we’re seeing very different patterns from what models suggest,” Charles Miller, of NASA’s Jet Propulsion Laboratory, said. “We saw large, regional-scale episodic bursts of higher-than-normal carbon dioxide and methane in interior Alaska and across the North Slope during the spring thaw, and they lasted until after the fall refreeze. To cite another example, in July 2012 we saw methane levels over swamps in the Innoko Wilderness that were 650 parts per billion higher than normal background levels. That’s similar to what you might find in a large city.”
If methane emissions from the Arctic permafrost via human-caused warming are beginning to rival those of major human sources, then we could be in for some rather serious trouble. CARVE’s mission is to find out if such a threat is emerging. Early observations are, as one NASA researcher put it, “both amazing and potentially troubling.”
The Clathrate Gun
Potentially even more troubling is the possibility that seabed methane stores locked in ice, known as clathrates, may also be starting to destabilize.
Worldwide, there is estimated to be between 1,600 and 2,000 gigatons of carbon locked in clathrates (or methane hydrates) on the bottom of the ocean. This is a massive store of carbon is at least two times the amount currently in the atmosphere. As with permafrost, if even a small amount of this methane reached the atmosphere, it would have powerful global warming impacts.
The problem is that human warming, via CO2 and other greenhouse gas emissions, is currently causing the world’s oceans to heat up. In fact, the oceans are accumulating heat faster than expected. You can see the pace of this increasing heat content in the graph below:
(Image source: Trenberth study)
And since clathrates are ice structures that are only stable in a narrow range of temperatures, any warming of the oceans, especially the deep oceans where clathrates are primarily stored, results in risk that the clathrates will melt, releasing their methane.
Unfortunately, we have emerging evidence showing that sea-bed clathrates are starting to destabilize. One set of evidence, produced by Shakhova, began to emerge in 2007. Shakhova’s study: Methane Release and Coastal Environment in The East Siberian Arctic Shelf illustrated how sea-bed methane in the region of the East Siberian Sea was venting into the ocean and even up through the thawing permafrost. A later survey of sea-bed methane releases, also conducted by Shakhova, found stunning one kilometer wide plumes of methane bubbling up from the ocean in the region of the East Siberian Arctic Shelf. In thhe report, published in The Independent, Igor Semiletov, Shakhova’s co-author, noted:
Earlier we found torch-like structures like this but they were only tens of metres in diameter. This is the first time that we’ve found continuous, powerful and impressive seeping structures more than 1,000 metres in diameter. It’s amazing,” Dr Semiletov said.
“I was most impressed by the sheer scale and the high density of the plumes. Over a relatively small area we found more than 100, but over a wider area there should be thousands of them,” he said.
Another study, this one conducted off the US East Coast, found that methane depositions on the Continental Shelf were also starting to destabilize. The study, published in Nature, showed that changes in the Gulf Stream and an unusual level of warming off the eastern seaboard of the United States was destabilizing a 10,000 square kilometer region rich in sea-bed methane. The study warned:
A changing Gulf Stream has the potential to thaw and convert hundreds of gigatonnes of frozen methane hydrate trapped below the sea floor into methane gas, increasing the risk of slope failure and methane release…
Evidence of Growing Trouble
Though not yet conclusive, the current permafrost studies by NASA and others combine with growing scientific evidence of sea-bed methane destabilization to provide a rather stark warning. Human warming via greenhouse gas emissions is beginning to push Earth to release some of her carbon stocks. These stocks, contained in tundra and sea-bed methane, are now showing signs of disturbance and are visibly starting to contribute to atmospheric carbon. It is worth noting that tipping points may be fast approaching and could run away from us rather rapidly.
As such, all efforts should be made to reduce worldwide human CO2 and methane emissions as rapidly as possible. Over the past 250 years, humans have contributed a large and growing forcing to the world’s climate. Now, emissions have grown to vast and dangerous levels even as Earth’s systems are reaching their carbon storage limits. Major feedbacks and threatening changes are likely in store if we don’t dramatically draw down emissions soon.
Evidence of methane coming from the Earth system should, therefore, serve as a warning, one we would well be wise to heed.