Greenhouse gases (GHGs) are compounds that trap heat in the Earth's atmosphere. The primary GHGs include carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases. Each of them have a different capacity to warm the atmosphere.
CO2, the most prevalent, is released through activities like burning fossil fuels, deforestation, and various industrial processes. Methane, with a higher warming potential but shorter atmospheric lifespan than CO2, emanates from natural sources like wetlands and human activities such as agriculture and waste management. Nitrous oxide, linked to agricultural and industrial activities, and fluorinated gases, used in refrigeration and manufacturing, also play significant roles in warming the atmosphere.
To compare the impact of different GHGs, scientists use the Global Warming Potential (GWP) metric, which quantifies how much a given amount of a particular gas contributes to global warming over a specified time, typically 100 years, compared to the same amount of CO2. This approach allows for a standardised assessment of emissions and helps inform strategies for reduction and mitigation.
How do we measure greenhouse gases?
Measuring carbon dioxide and other greenhouse gases in the atmosphere involves a combination of direct measurements, remote sensing technologies, and modeling techniques.
Direct Measurements
Surface-Based Monitoring Stations: Networks of monitoring stations around the world, such as those operated by the National Oceanic and Atmospheric Administration (NOAA) and the Scripps Institution of Oceanography, directly measure CO2 and other greenhouse gases. These stations use air sampling equipment to continuously monitor the concentration of gases in the atmosphere. The Mauna Loa Observatory in Hawaii, for example, has been measuring atmospheric CO2 since 1958, providing the longest continuous record of direct measurements.
Airborne and Shipboard Sampling: Scientists collect air samples from aircraft and ships to measure greenhouse gas concentrations at different altitudes and locations. These samples help fill in the gaps in surface-based networks, especially in remote areas.
Remote Sensing Technologies
Satellites: Satellites equipped with specialised sensors can measure concentrations of greenhouse gases across the globe. Instruments like the Orbiting Carbon Observatory-2 (OCO-2), launched by NASA, are designed to map global CO2 levels, offering insights into how CO2 is moving through the Earth system.
Ground-Based and Airborne Lidar: Light Detection and Ranging (LIDAR) technology can be used from the ground or aircraft to measure greenhouse gases. This technology sends out laser light pulses and measures how they are reflected back to the sensor, providing data on gas concentrations.
Modeling Techniques
Atmospheric Models: Scientists use computer models to simulate the transport and chemical reactions of greenhouse gases in the atmosphere. These models incorporate data from direct measurements and remote sensing to estimate gas concentrations in areas where direct observations are scarce.
Inventories and Statistical Models: Countries and organizations compile inventories of greenhouse gas emissions from various sources (e.g., energy production, transportation, agriculture). These inventories, based on statistical models and activity data, help estimate the amount of gases released into the atmosphere.
Integration of Data
Global Monitoring Networks: Integrating data from multiple sources, including surface stations, aircraft, ships, and satellites, provides a comprehensive view of greenhouse gas concentrations in the atmosphere. International collaborations, such as the Global Atmosphere Watch (GAW) program coordinated by the World Meteorological Organization (WMO), play a crucial role in compiling and analyzing this data.Top of Form