What is the primary environmental consequence of excess carbon dioxide in the atmosphere?

The primary environmental consequence of excess carbon dioxide in the atmosphere is global warming. This occurs because carbon dioxide is a greenhouse gas, which means it has the ability to absorb and emit infrared radiation. When there is an increase in the concentration of carbon dioxide due to human activities such as burning fossil fuels, deforestation, and industrial processes, it enhances the greenhouse effect.

This enhanced greenhouse effect leads to an increase in Earth's average temperatures, causing a variety of environmental changes. These changes include rising sea levels, melting glaciers and polar ice, and shifts in weather patterns, which can result in more extreme weather events such as heatwaves, storms, and floods.

Understanding the role of carbon dioxide in this process is crucial, as it helps clarify why addressing carbon emissions is a key focus in efforts to combat climate change and mitigate its impacts on the environment and society. Other options, while significant in their own right, do not directly stem from carbon dioxide's environmental impact in the same way that global warming does.