Global warming refers to the long-term rise in the average temperature of the Earth’s atmosphere and oceans. It primarily refers to the warming observed since the pre-industrial period, which is mainly caused by human activities and the increasing concentration of greenhouse gases in the atmosphere.

During the 20th century, the global average temperature increased significantly. Since the pre-industrial period (1850–1900), the global surface temperature has risen by approximately 1.1 degrees Celsius. Scientific evidence shows that human activities, particularly the burning of fossil fuels and the resulting increase in greenhouse gas emissions, are the principal cause of the warming observed since the mid-20th century.

The rising concentrations of carbon dioxide and other greenhouse gases are the primary human-induced factors contributing to global warming. Activities such as burning fossil fuels, deforestation, and agriculture increase greenhouse gas concentrations and intensify the greenhouse effect.

Since the Industrial Revolution, carbon dioxide concentrations in the atmosphere have increased substantially. Although plants and the oceans absorb a significant portion of the carbon dioxide released by human activities, these natural processes do not remove all of the additional carbon dioxide, and atmospheric concentrations have continued to rise.

Global warming can lead to many other changes, including rising sea levels and changes in the amount and patterns of rainfall and snowfall. Climate change is also contributing to changes in extreme weather, including more frequent and intense heat waves and heavier precipitation in many regions. Other consequences include changes in crop yields, retreating glaciers and ice sheets, changes in river flows, shifts in the distribution of plant and animal species, and increased risks to human health.

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