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ACAMC Key Findings
ABRUPT CHANGES IN THE EARTH’S CLIMATE SYSTEM
ABRUPT CHANGE IN ATMOSPHERIC
- The main concerns about abrupt changes in atmospheric methane (CH4) stem from (1) the large quantity of methane believed to be stored as methane hydrate in the sea floor and permafrost soils and (2) climate-driven changes in methane emissions from northern high-latitude and tropical wetlands.
- The size of the methane 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 judgement about those risks.
- There are a number of suggestions in the scientific literature about the possibility of catastrophic release of methane to the atmosphere based on both the size of the hydrate reservoir and indirect evidence from paleoclimatological studies. However, modeling and detailed studies of ice cores methane so far do not support catastrophic methane releases to the atmosphere in the last 650,000 years or in the near future. A very large release of methane may have occurred at the Paleocene-Eocene boundary (about 55 million years ago), but other explanations for the evidence have been offered.
- The current network of atmospheric methane monitoring sites is sufficient for capturing large-scale changes in emissions, but it is insufficient for attributing changes in emissions to one specific type of source.
- Observations show that there have not yet been significant increases in methane emissions from northern terrestrial high-latitude hydrates and wetlands resulting from increasing Arctic temperatures.
- Catastrophic release of methane to the atmosphere appears very unlikely in the near term ( e.g., this century). However, it is very likely that climate change will accelerate the pace of chronic emissions from both hydrate sources and wetlands. The magnitude of these releases is difficult to estimate with existing data. Methane release from the hydrate reservoir will likely have a significant influence on global warming over the next 1.000 to 100,000 years.
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