What is considered one of the greatest environmental issues of the late 20th century?

The Greenhouse Effect is often regarded as one of the most significant environmental issues of the late 20th century due to its profound implications for climate change and global warming. This phenomenon occurs when certain gases in the Earth's atmosphere, such as carbon dioxide, methane, and nitrous oxide, trap heat from the sun, preventing it from escaping back into space. As human activities, particularly the burning of fossil fuels and deforestation, have significantly increased the concentration of these greenhouse gases, concerns about rising global temperatures, melting ice caps, and changing weather patterns have become prevalent.

During the late 20th century, scientific research began to highlight the potential impacts of the Greenhouse Effect on ecosystems, sea levels, and weather extremes. This led to increased public awareness and prompted international efforts, such as the Kyoto Protocol and subsequent agreements, aimed at addressing climate change through the reduction of greenhouse gas emissions.

In contrast, while the depletion of the ozone layer and the increased use of chlorofluorocarbons (CFCs) are critical environmental issues, they primarily focus on the protection of the stratospheric ozone layer, which shields the Earth from harmful ultraviolet radiation. The increased amount of oxygen in the atmosphere is not considered an environmental issue of concern; rather