Greenhouse Effect

The greenhouse effect is the process by which heat is trapped near Earth’s surface by greenhouse gases which envelope the planet. The Earth’s natural greenhouse effect maintains an average temperature of 15°C, which helps life thrive.

Three factors influence how much any one greenhouse gas influences the greenhouse effect: how much of the gas exists in the atmosphere; how long the gas remains trapped in the atmosphere; and how effective the gas is at trapping heat.

Higher concentrations of greenhouse gases (particularly carbon dioxide) are causing extra heat to be trapped and average global temperatures to rise. As of 2023, the concentration of carbon dioxide in the atmosphere has reached more than 420 parts per million, which is 50% higher than pre industrial levels.(2)

Human activities emit four major greenhouse gases: carbon dioxide, methane, nitrous oxide, and halocarbons. These gases accumulate in the atmosphere and alter Earth’s energy balance. Radiative forcing measures how these gases and other factors change the amount of energy trapped in the climate system. While natural influences like solar variation and volcanic eruptions play a role, the radiative forcing from human activities is far larger and is the dominant driver of current and future climate change.

The greenhouse effect was understood gradually through the work of several scientists. Fourier (1824) and Pouillet (1836) first proposed that the atmosphere traps heat, and Eunice Foote (1856) provided early experimental evidence that carbon dioxide and moist air absorb heat. John Tyndall’s 1859 experiments offered the first precise demonstration that gases like CO₂ and water vapour absorb and emit infrared radiation, establishing the physical mechanism behind atmospheric warming.

Our modern understanding rests on many contributors. While Tyndall’s work became foundational, earlier insights and Foote’s overlooked experiments show that the discovery was cumulative. Today, thousands of scientists continue refining this knowledge to deepen our understanding of climate change.(4)

Venus offers an example of how extreme the greenhouse effect can become. Billions of years ago it may have resembled Earth, but a runaway greenhouse effect vaporised its oceans, allowed water to escape into space, and left the planet with an atmosphere that is 96% carbon dioxide and surface temperatures around 450°C. Earth is not expected to follow this path even if all fossil fuels were burned, but Venus shows why avoiding climate tipping points matters.

Understanding how greenhouse gases warm the planet is essential for preventing dangerous change, and international standards help guide credible action. The greenhouse effect explains why managing emissions is central to climate stability, and frameworks such as ISO 14064 support governments and organisations in measuring, reporting and verifying their emissions as part of net‑zero strategies.(5)

Scientists measure greenhouse gases mainly by analysing how they absorb light. Spectroscopy shines infrared radiation through air samples to identify gases by their unique absorption patterns, and long‑running stations such as Mauna Loa track global carbon dioxide levels from remote locations to avoid contamination from nearby sources. Satellites use the same principles from space, measuring gases along the path of reflected light to map regional emissions, and these modern observations can be compared with historical records such as ice cores to understand how atmospheric composition has changed over time.