According to scientific research, the greenhouse effect refers to the natural process by which certain gases in the atmosphere absorb and re-emit infrared radiation, warming the Earth’s surface and lower atmosphere. The natural greenhouse effect makes Earth habitable; however, human activities have increased the concentration of greenhouse gases in the atmosphere, strengthening the greenhouse effect and causing global warming.

The greenhouse effect is primarily associated with greenhouse gases such as carbon dioxide, methane, nitrous oxide, and water vapor. These gases absorb some of the infrared radiation emitted by the Earth’s surface and re-emit it in different directions, including back toward the surface. As greenhouse gas concentrations increase, more energy is retained within the climate system, causing the Earth’s average temperature to rise.

Solar radiation consists primarily of shorter-wavelength radiation, while the Earth’s surface emits energy primarily as longer-wavelength infrared radiation. The atmosphere is relatively transparent to much of the incoming solar radiation but absorbs some of the infrared radiation emitted by the Earth’s surface.

During the day, sunlight reaches the Earth, and some of its energy is reflected back into space while the rest is absorbed by the atmosphere, land, and oceans.

The Earth’s surface continuously emits infrared radiation. Some of this radiation passes through the atmosphere and escapes into space, while greenhouse gases absorb and re-emit some of it. This process helps keep the Earth’s surface warmer than it would otherwise be.

The greenhouse effect is sometimes compared with the glass of a greenhouse, although the actual atmospheric process is different. Without the natural greenhouse effect, Earth would be much colder and less suitable for life. The increase in greenhouse gases caused by human activities has strengthened this natural effect and increased the amount of heat stored in the climate system.

As the concentration of greenhouse gases in the atmosphere increases, the Earth’s average temperature rises. This warming can lead to a number of changes, including:

Glaciers and ice sheets lose mass, contributing to rising sea levels and increasing risks to low-lying coastal areas.

Snow cover and the amount of water stored as snow and ice can decline, changing the timing and availability of water in some river systems.

Warming can alter the distribution and seasonal cycles of plants and animals, disrupt ecosystems, and change relationships within food webs.

作者：Michael Chiu，MWS，CI
Previously published in Ming Pao Daily News – Updated and Revised in 2026