Trace gases refer to gases that make up a very small proportion of the Earth's atmosphere, typically less than 1% by volume. These gases play a crucial role in regulating the Earth's climate and air quality. Examples of trace gases include ozone, carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons. Researchers studying trace gases are interested in understanding their sources, sinks, transport, and interactions with the atmosphere. They investigate how changes in these gases can impact climate change, air quality, and human health. This research is important for developing policies and strategies to mitigate the effects of climate change and air pollution.