A recent article
Here's a little background on the problem. Total atmospheric methane levels have been steadily increasing along with carbon dioxide. Around 2000, they temporarily leveled, then sharply increased in 2007. One National Oceanic and Atmospheric Administration scientist attributes this latest increase probably to the dramatic increase of China's coal burning, and an increase in tropical and arctic wetlands' emissions. The vast reservoirs of frozen methane hydrates on the Siberian continental shelf started to show signs of melting around 2005, according to data gathered by Russian scientists. If these reservoirs begin to melt fast enough, significant amounts of methane, a far more potent greenhouse gas than carbon dioxide, could be released to the atmosphere over nine years, the average lifetime of methane in the atmosphere. In terms of climate change this could be an explosive release and possibly powerful enough to catastrophically accelerate global warming beyond anything yet predicted.
Being curious scientists, we naturally went back to the original USGS report to see exactly on what they based their conclusions. What we found dissolved any complacency:
The size of the hydrate reservoir is uncertain, perhaps by up to a factor of 10. Because the size of the reservoir is directly related to the perceived risks, it is difficult to make certain judgment about those risks.
Observations show that there have not yet been significant increases in methane emissions from northern high-latitude hydrates and wetlands resulting from increasing arctic temperatures. Although there are a number of suggestions in the literature about the possibility of a dramatic abrupt release of methane to the atmosphere, modeling and isotopic fingerprinting of ice-core methane do not support such a release to the atmosphere over the last 100,000 years or in the near future...
Acceleration of persistent release from hydrate reservoirs is likely, but its magnitude is difficult to estimate.
The USGS notes further that "most of the marine hydrate reservoir will be insulated from anthropogenic climate change. The exception is in shallow ocean sediments... [which] will very likely respond to anthropogenic climate change with an increased background rate of sustained methane release, rather than an abrupt release." (p. 58.) The USGS fails to explain what it considers a dramatic abrupt release. Giant bubbles bursting out of the oceans daily or a large release over a decade? Both would be dramatic and abrupt in terms of climate change. This statement on page 58 is contradicted later on in the same report, however, where an information box states that "It is important to note, however, that most marine methane hydrates are found in shallow water near continental margins." (p. 388.) If this latter statement is true, most of the marine hydrate reservoir will not be insulated from climate change. But which statement is true?
What is the USGS really saying about Arctic methane emissions? Simply this: they don't know what the risk of an explosive release of methane really is, but their models suggest that it's small. Indeed, after reviewing all the possible significant methane sources such as tropical wetlands, the USGS uses the words, "very unlikely" (p. 60), which translates, using their table of vocabulary of uncertainties, into less than 10%.
Our antennae immediately went up, because a model is only as good as the assumptions and data that go into creating and running it. As noted in the second paragraph of the above quote from pp. 32-3, the USGS is not acknowledging and thus is not using in their modeling the recent data from Norwegian and Russian scientists that already show significant increases in atmospheric methane in areas over the submarine hydrate beds off Siberia. In the one table showing sources of methane emissions for 2003, there is no mention of this source. Indeed, one of the USGS recommendations is to set up monitoring of methane emissions from these submarine beds, something the Russians have been doing at least intermittently since the 1990s. Current US monitoring can only track large scale emissions, not the specific sources of those emissions, according to the report.
Another crucial piece of information that would go into a model that predicts the release of methane into the atmosphere from frozen hydrates would be the size of the source. Although the USGS admits the source is large, they do not know the size of the source accurately.
So what data IS the USGS modeling based on? The data from ice core methane - that is, the methane stored many thousands of years ago in ancient ice, and that form a climatic record of the previous planetary warming. Data from the last time Earth experienced a large, abrupt climate warming, around 20,000 years ago, indicate that a slight change in Earth's orbit caused an initial warming that then caused either oceans, soils, or both to release carbon dioxide and methane, both greenhouse gases, into the atmosphere. This caused further warming that stimulated yet further feedback emissions of greenhouse gases from ecosystems, a process that continued over thousands of years, and resulted in an overall increase of over five degrees Celsius in global temperature. Data further indicate that the source of the methane was not from hydrate deposits.
This might be an accurate picture of methane behavior during the previous planetary warming event, but there are significant differences between it and the current one. The current rate at which global temperatures and atmospheric carbon dioxide levels are increasing is MUCH faster - happening over decades, not millenia. Furthermore, the current starting temperature is significantly higher than it was at the beginning of the last warming event. Both factors could create a significantly different pattern of further feedbacks so that the consequences might not be comparable to any past event, including the last one. For example, a higher initial temperature requires less warming to reach a temperature that could trigger melting of methane hydrate deposits, which could then trigger a large increase in atmospheric methane levels and further warming.
To the credit of the USGS, they are recommending that the US support research to gather important data: the size of vulnerable methane deposits, and the rate at which methane is being emitted from them, for example. Ultimately, however, the USGS has no good scientific basis for currently estimating the threat of an explosive release of methane from melting submarine deposits. The real answer is: we simply do not have enough data to know, and we shouldn't wait to find out: the climate crisis must be solved as soon as possible for the prosperity of humanity. For more details on this, other global warming consequences, and the range of solutions available, all described in plain English, read the free, downloadable book, Cool The Earth, Save the Economy, available at: www.CoolTheEarth.US.
1. Eilperin, J. 2008. Agencies' report warns of faster climate change. The Los Angeles Times, December 26, 2008. http://www.latimes.com/news/nationworld/nation/la-na-climate26-2008dec26,0,4065663.story retrieved December 30, 2008.
2. Brennan, W. et al. 2008. Abrupt Climate Change: Final Report, synthesis and Assessment Product 3.4. USGS, NOAA, and NSF. U. S. Climate Change Science Program and the Subcommittee on Global Change Research. December 16, 2008. A downloadable copy is available at: http://www.climatescience.gov/default.php retrieved December 30, 2008.
3. NOAA. 2008. Carbon dioxide, methane rise sharply in 2007. National Oceanic and Atmospheric Administration, April 23, 2008. http://www.noaanews.noaa.gov/stories2008/20080423_methane.html retrieved December 30, 2008.
4. Shakova, N. et al. 2005. The distribution of methane on the Siberian Arctic shelves: implications for the marine methane cycle. Geophysical Research Letters Vol. 32: L09601 doi:10.1029/2005GL022751, 2005 http://www.agu.org/pubs/crossref/2005/2005GL022751.shtml retrieved December 31, 2008.
See also: Mrasek, V. 2008. Melting methane: a storehouse of greenhouse gases is opening up in Siberia. Der Spiegel, April 17, 2008. http://www.spiegel.de/international/world/0,1518,547976,00.html retrieved December 31, 2008.
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