Greenhouse Effect
The greenhouse effect is the warming that happens when gases in the atmosphere absorb infrared radiation leaving the Earth's surface and re-emit part of it back downward. Without it the planet's average surface temperature would be about 33°C colder.
Sunlight passes through the atmosphere and warms the surface. The surface radiates that energy back out as infrared. Water vapour, carbon dioxide, methane, nitrous oxide, and other greenhouse gases absorb some of that outgoing radiation and send part of it back down. The effect is natural and it is what makes the planet habitable.
The problem is the enhanced greenhouse effect. Adding CO₂ and other gases raises the concentration of absorbers, so less heat escapes and the surface warms until the energy balance is restored. Gases differ in how strongly they absorb and how long they persist, which is what global warming potential measures. Methane traps far more heat per tonne than CO₂ over twenty years but breaks down within about a decade.
For a reporting team this is the reason an inventory is not just a CO₂ count. Refrigerant leaks, methane from waste, and nitrous oxide from fertilizer all have to be converted to CO₂ equivalent using published GWP values, and the choice of GWP time horizon changes the total. The GHG Protocol specifies which values to use, so the same activity produces a comparable number across companies.
Frequently asked questions
What is the greenhouse effect? +
The greenhouse effect is the warming caused when atmospheric gases absorb infrared radiation leaving the Earth's surface and re-emit part of it downward. It keeps the planet roughly 33°C warmer than it would otherwise be.
What is the enhanced greenhouse effect? +
The enhanced greenhouse effect is the extra warming caused by human emissions of carbon dioxide, methane, nitrous oxide, and fluorinated gases, which raise the concentration of heat-absorbing gases in the atmosphere.
Which gases cause the greenhouse effect? +
Water vapour, carbon dioxide, methane, nitrous oxide, ozone, and fluorinated gases such as HFCs and SF₆. Corporate inventories report the human-made gases and convert them to CO₂ equivalent using global warming potential.
Related terms
Greenhouse Gas (GHG)
Greenhouse gases are atmospheric gases that trap infrared radiation and warm the Earth's surface. The six main GHGs covered by the Kyoto Protocol are carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆). The Kigali Amendment added nitrogen trifluoride (NF₃).
Global Warming Potential (GWP)
Global warming potential (GWP) is a metric that compares the warming effect of a greenhouse gas relative to CO₂ over a specified time horizon, typically 100 years (GWP-100). It is published by the IPCC and used to convert different greenhouse gases into CO₂ equivalent for emissions inventories.
Carbon Cycle
The carbon cycle is the continuous movement of carbon between the atmosphere, oceans, soil, rock, and living things. Burning fossil fuels releases carbon that was locked underground for millions of years, and it enters the atmosphere far faster than natural processes remove it.
tCO₂e (Tonnes of CO₂ Equivalent)
tCO₂e — tonnes of carbon dioxide equivalent — is the standard unit for expressing greenhouse gas emissions. It normalizes different greenhouse gases (methane, nitrous oxide, HFCs, etc.) to their equivalent warming impact relative to CO₂ using global warming potentials (GWPs), allowing them to be summed into a single comparable metric.
Carbon Accounting
Carbon accounting is the systematic process of measuring, recording, and reporting the greenhouse gas (GHG) emissions produced by an organization, product, or activity. It follows standardized methodologies — most commonly the GHG Protocol — to quantify emissions across Scope 1 (direct), Scope 2 (purchased energy), and Scope 3 (value chain) categories, producing an auditable inventory that underpins disclosure, reduction planning, and regulatory compliance.