Final answer:
The atmosphere's changing composition is primarily due to human activities that have intensified the greenhouse effect, leading to global warming. Consequences include sea level rise, extreme weather events, and resource scarcity. Mitigation involves shifting towards sustainable energy sources to reduce greenhouse gas emissions.
Step-by-step explanation:
The nature and cause of the atmosphere's changing composition can be largely attributed to human activities, particularly since the Industrial Revolution. These activities have resulted in increased emissions of greenhouse gases like carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), enhancing the natural greenhouse effect. This effect is critical for life on Earth as it helps maintain the planet's temperature. However, the intensification of this effect due to human activities is causing global warming.
Global warming leads to a host of possible consequences. Among these are rising sea level rise due to melting polar ice caps and glaciers, more frequent and severe weather events like hurricanes, and desertification. Increased temperatures can also affect food production and water availability, potentially leading to shortages and conflicts over resources.
To mitigate the effects of global warming, there is a pressing need to reduce carbon emissions by moving away from fossil fuels towards cleaner, more sustainable sources of energy. This transition is crucial in order to stabilize greenhouse gas concentrations in the atmosphere and limit the rise in global temperatures, thereby reducing the risks and impacts associated with climate change.