Greenhouse gases are molecules in our atmosphere that absorb the heat radiating from Earth’s surface, preventing it from being emitted into space. These gases are natural and synthetic, and they include water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and a suite of halogen-bearing gases including chlorine, bromine, fluorine and sulphur hexafluoride (SF6).
Greenhouse gas emissions from human activities have been increasing since the Industrial Revolution, and are responsible for global warming and changing climate patterns that affect us all. It’s essential that we understand the role these gases play and take actions at every level to reduce their impact.
The main source of long-lived greenhouse gases in the atmosphere is the breakdown of organic matter in vegetation, soils and oceans, with contributions from livestock, fossil fuel combustion and industry also significant. NOAA’s air monitoring network samples the main long-lived GHGs at more than 50 cooperative sites worldwide each year. These are then analysed in our state-of-the-art laboratories to measure their concentrations and to produce estimates of the atmospheric lifetimes and Global Warming Potentials, or GWPs, for each gas.
These are expressed as a figure of the amount of warming they cause, relative to CO2 over a 100-year period. It is important to remember that these values are approximate, as they are based on the known physical properties of each gas, its atmospheric removal mechanisms (sinks) and current scientific knowledge on their radiative behaviour and properties.