Greenhouse gases trap some of the solar energy that heats Earth’s surface by keeping it closer to Earth instead of radiating it out into space. They do this by absorbing and retaining thermal infrared radiation. This is what gives them their warming effect, which is why they are known as greenhouse gases. These gases are present in the atmosphere all over the world. Some have been released by natural processes, while others have been added by human activities since the Industrial Revolution. Carbon dioxide, methane, and nitrous oxide are the main human-caused greenhouse gases. They are each important contributors to global warming, but each has a different impact on the climate system. This is mainly due to differences in their atmospheric lifetimes and radiative properties.
Greenhouse gas concentrations have increased steadily over the past few decades, largely due to human fossil fuel combustion. CCGG researchers monitor concentrations of these gases in the atmosphere using ground-based and satellite instruments. Every spring, they calculate and release the preliminary global average levels of the three primary long-lived greenhouse gases – CO2, methane and nitrous oxide – observed during the previous year.
These results are made available to the scientific community and used in climate models to understand how they influence the Earth’s climate. They are also useful for estimating greenhouse gas emissions and removals, and monitoring trends in atmospheric concentrations. CCGG operates the Global Greenhouse Gas Reference Network, which consists of over 50 cooperative sampling sites around the globe.