The greenhouse effect is a natural process where atmospheric gases trap heat – a phenomena that allows the Earth to retain enough solar heat to be livable. Without the greenhouse effect, the Earth would not support most forms of life.
How Does the Greenhouse Effect Work?
Although the process is complex, the greenhouse effect can be described fairly simply:
Sunlight passes through the atmosphere. Clouds, ice caps and other light-colored surfaces reflect some light back into space, but most of the incoming energy reaches the planet’s surface. The Earth radiates heat back toward space. Greenhouse gases in the atmosphere absorb that heat, bouncing some back to the Earth’s surface and releasing some into the atmosphere.
What are Greenhouse Gases?
Greenhouse gases include carbon dioxide, methane, nitrous oxide and other gases that accumulate in the atmosphere and create the heat-reflective layer that keeps the Earth at a livable temperature. These gases form the insulation that keeps the planet warm enough to support life.
Some of the most common — and worrisome — greenhouse gases are:
- Carbon dioxide, which is emitted whenever coal, oil, natural gas and other carbon-rich fossil fuels are burned. Although carbon dioxide is not the most powerful greenhouse gas, it is the largest contributor to climate change because it is so common. In order to reduce carbon dioxide emissions, we need to reduce the amount of fuel we use in our cars, homes, and lives.
- Methane is caused by the decomposition of plant matter, and is released from landfills, swamps, rice paddies. Cattle also release methane. Although methane emissions are lower than carbon dioxide emissions, it is considered a major greenhouse gas because each methane molecule has 25 times the global warming potential of a carbon dioxide molecule.
- Nitrous oxide is released from bacteria in soil. Modern agricultural practices — tilling and soil cultivation, livestock waste management, and the use of nitrogen-rich fertilizers — contribute significantly to nitrous oxide emissions. A single nitrous oxide molecule has 298 times the global warming potential of a carbon dioxide molecule.
- Additional greenhouse gases include hydrofluorocarbons (1,430-14,800 time the global warming potential of carbon dioxide), sulfur hexafluoride (22,800 times the global warming potential of carbon dioxide), and water vapor.
- Learn more about “climate forcing” greenhouse gases.
If the Greenhouse Effect is Natural, Then What’s the Problem with Greenhouse Gases?
Modern climate change is caused by an excess of greenhouse gases. This, in turn, over-insulates the planet. As a result, temperatures rise. Imagine wearing a winter parka in the tropics. The effect is similar — too much insulation causes the planet to overheat, which has already begun to change the climate. Learn more about the impacts of climate change.
The Earth has a natural greenhouse effect due to trace amounts of water vapour (H2O), carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) in the atmosphere. These gases let the solar radiation reach the Earth’s surface, but they absorb infrared radiation emitted by the Earth and thereby lead to the heating of the surface of the planet. One needs to distinguish between the natural greenhouse effect and the enhanced greenhouse effect. The natural greenhouse effect is caused by the natural amounts of greenhouse gases, and is vital to life. In the absence of the natural greenhouse effect the surface of the Earth would be approximately 33 °C cooler. The enhanced greenhouse effect refers to the additional radiative forcing resulting from increased concentrations of greenhouse gases induced by human activities. The main greenhouse gases whose concentrations are rising are carbon dioxide, methane, nitrous oxide, hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs) and ozone in the lower atmosphere.
The Global Atmosephere Watch (GAW) observes, analyses and publishes greenhouse gas data collected by fifty countries around the globe from the High Arctic to the South Pole. The greenhouse gases monitored include:
- Carbon Dioxide (CO2) (incl. Δ14C, δ13C and δ18O in CO2, and O2/N2 Ratios)
- Methane (CH4)
- Nitrous Oxide (N2O)
- Halocarbons and SF6
- Molecular Hydrogen (H2)
The data are collected and distributed by the World Data Centre for Greenhouse Gases (WDCGG) at the Japan Meteorological Agency. The GAW Scientific Advisory Group for Greenhouse Gases (SAG-GHG) advises on the programme development. GAW issues the annual Greenhouse Gas Bulletin, which reports on the latest trends and atmospheric burdens of the most influential, long-lived greenhouse gases, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), as well as a summary of the contributions of the lesser gases.