What is the primary consequence of excessive carbon dioxide in the atmosphere?

The primary consequence of excessive carbon dioxide in the atmosphere is global warming. This occurs because carbon dioxide is a significant greenhouse gas, which means it has the ability to trap heat in the Earth's atmosphere. As the concentration of carbon dioxide increases due to human activities such as burning fossil fuels, deforestation, and industrial processes, more heat is retained, leading to a rise in global temperatures.

This increase in temperature can cause a variety of environmental changes, including altered weather patterns, melting glaciers and polar ice, rising sea levels, and more frequent and severe weather events. The overall impact of global warming can be widespread, affecting ecosystems, sea life, and weather systems around the world.

Other options, while related to environmental issues, do not primarily stem from the excessive presence of carbon dioxide. For example, ozone depletion is largely caused by chlorofluorocarbons (CFCs), acid rain is primarily the result of sulfur and nitrogen oxides, and deforestation is mainly driven by land use changes for agriculture, urbanization, and logging. Thus, while all of these factors are significant environmental concerns, global warming directly arises from the accumulation of carbon dioxide in the atmosphere.