Which of the following is NOT true concerning Earth's atmosphere?

The statement regarding the upper atmosphere destroying harmful gases like methane is not true. While the upper atmosphere does have some processes that can break down certain pollutants, such as ozone reacting with some organic compounds, it is not particularly effective at destroying methane. Methane is relatively stable in the atmosphere and does not break down significantly in the upper atmosphere; instead, its primary degradation occurs through reactions with hydroxyl radicals (OH) in the troposphere. The lifetime of methane in the atmosphere can span several years, and it can contribute to the greenhouse effect.

In contrast, greenhouse gases—like carbon dioxide and methane—are critical in maintaining Earth's average temperature by trapping heat. Ozone plays a significant role in the stratosphere, where it absorbs the majority of the sun's harmful ultraviolet radiation. Moreover, oxygen levels in the atmosphere are indeed sufficient to support the diverse array of life forms on Earth, as they require oxygen for processes like respiration. Overall, the untruth about the upper atmosphere's role in destroying methane sets this statement apart from the others, which accurately reflect aspects of Earth's atmospheric processes and conditions.