Question

Select the greenhouse gas that fits the following description: It is the largest contributor to greenhouse warming. Over the course of human history, its concentration in the atmosphere has not changed much, but it varies considerably from place to place.

a. Carbon dioxide
b. Water vapor
c. Nitrous oxide
d. Methane

Answer 1

Water vapor (H₂O) is the greenhouse gas that matches the provided description and is the largest contributor to the natural greenhouse effect, while methane (CH₄) has seen significant concentration increases due to human activity.

Step-by-step explanation:

The greenhouse gas that fits the description of being the largest contributor to greenhouse warming, having not changed much over the course of human history, and varying considerably from place to place is water vapor (H₂O). Water vapor is the most abundant greenhouse gas and it substantially contributes to the natural greenhouse effect.

While its concentration does not change drastically due to direct human activities, it is influenced by local temperatures which affect evaporation and precipitation rates. Unlike water vapor, methane (CH₄) concentrations have increased significantly due to human activities. Although it exists in smaller quantities than carbon dioxide, methane is approximately 21 times more effective per molecule at warming the atmosphere and contributes about 20 percent of the enhanced greenhouse effect.