Which phenomenon is characterized by the gradual rise in Earth’s average temperature?

The phenomenon characterized by the gradual rise in Earth's average temperature is known as global warming. This term specifically refers to the long-term increase in average surface temperatures on Earth, predominantly caused by the accumulation of greenhouse gases in the atmosphere due to human activities, such as burning fossil fuels and deforestation.

Global warming is a significant aspect of climate change, which encompasses a broader range of changes in the Earth's climate system. While climate change includes shifts in weather patterns, extreme weather events, and various environmental impacts, global warming specifically addresses the increase in temperature.

The greenhouse effect, while related, describes the natural process where certain gases trap heat in the atmosphere, keeping the planet warm enough to sustain life. However, global warming indicates that this process is being intensified by human actions, leading to a rise in average temperatures.

Ozone depletion refers to the thinning of the ozone layer in the Earth's stratosphere, resulting mainly from human-made chemicals. It primarily affects ultraviolet radiation levels reaching the surface rather than directly leading to temperature increases.

In summary, global warming directly correlates to the rise in Earth's average temperatures, distinguishing it as the correct answer.