Methane, which occurs at about 1.8 ppm by volume in the atmosphere of Earth, is considered the third most important greenhouse gas. According to the US Environmental Protection Agency, methane is 21 times more effective at trapping heat in the atmosphere than CO2 by weight, over a 100-year period. Present estimates are that methane accounts for about 20% of the total forcing potential of all long-lived greenhouse gases. Although atmospheric methane levels are up about 150% over the last 250 years, they have been relatively stable in the last decade.
One reason scientists conduct methane analysis is to assess methane emissions in response to large-scale climate change events in the past. For example, scientists study methane preserved in ice cores to determine how atmospheric methane levels changed as the climate entered and exited the ice ages. While climate trends of the past can tell us a fair amount about what to expect in future climate change scenarios, they are no substitute for detailed data on present atmospheric methane exchange. As a result, scientists around the world are collecting data to help quantify the exchange of methane between ecosystems and the atmosphere.
While the regions that contribute most to atmospheric methane have been identified, the exact contribution of each region is not known in most cases. Current climate models use proxy data or extrapolation from a relatively small number of direct measurements to estimate methane emissions. This data has obvious value, but could be improved significantly with widespread direct measurements. Accurate measurements of methane fluxes will help reduce uncertainty in climate models and lead to a more comprehensive understanding of carbon cycles.
In addition, methane monitoring will be an important component of a greenhouse gas regulatory framework. Methane monitoring on a widespread scale may be necessary in order to ensure that a cap and trade system is effective, reduce the number of errors, and identify fraudulent activity. One solution to this challenge is direct measurement of ambient methane levels in a monitoring network. Such a network would require high-precision instrumentation to be deployed in a scientifically valid framework, with infrastructure and capacity for analysis of the data.
To help meet these needs, the LI-7700 Open Path CH4 Analyzer is available to measure methane densities in fluxes from methane emitting ecosystems. Using widely accepted techniques, such as the eddy covariance method, the LI-7700 can provide data that is required to improve existing global climate models and develop a more detailed understanding of methane fluxes between the earth and atmosphere.
Monitoring Trace Gases in Soil
LI-COR long-term soil CO2 flux chambers (8100-104 Long-Term Chamber and 8100-104C Clear Long-Term Chamber) are designed to be left in the field for extended lengths of time to make unattended flux measurements. Originally designed to be used with the LI-8100A Automated Soil CO2 Flux System for monitoring soil CO2 fluxes, these chambers can also be operated independently, using a simple Transistor-transistor logic (TTL) controller and a 12 VDC supply. When used independently, these chambers can be combined with trace gas analyzers, allowing for long term unattended monitoring of trace gas fluxes. For more information, visit the Trace Gases in Soil application page.
LI-COR also offers a Trace Gas Sampling Kit (p/n 8100-664) for use with the LI-8100A Automated Soil CO2 Flux System and both long-term and survey chambers. With the 8100-664, a septum can be placed in-line between the chamber and the LI-8100A Analyzer Control Unit, and used to manually sub sample the chamber head space at various times throughout a flux measurement. Typically, samples are drawn into a gas-tight syringe and analyzed using a gas chromatograph.
- Solar Power for EC Flux Stations
Introduction to the calculations, components, and design of a basic off-grid solar power system for eddy covariance research.
- GHG System Quick Start Guide
Short instructions to wire sensors and configure the instruments in GHG-1 or GHG-2 CO2, H2O, and CH4 eddy covariance flux systems.
- Methane Emissions From the Arctic Coastal Plain in Alaska
- Measurements of Methane Flux Using a Fast Open-Path Analyzer
- Open-Path Measurements of CH4 Flux Using Eddy Covariance Technique
- Measuring Principles of the LI-7700 Trace Gas Analyzer
Presenters: Bill Miller, Brad Riensche