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Global warming refers to the long-term increase in Earth's average surface temperature due to human activities, primarily the emission of greenhouse gases such as carbon dioxide, methane, and nitrous oxide. These gases trap heat in the atmosphere, leading to a greenhouse effect that causes the planet to warm.

The primary source of these greenhouse gases is the burning of fossil fuels for energy and transportation. Deforestation also contributes to global warming, as trees that absorb carbon dioxide are cut down. As a result, the concentration of greenhouse gases in the atmosphere has risen significantly since the Industrial Revolution.

Global warming has various impacts on the environment and human society. It leads to melting ice caps and glaciers, rising sea levels, and more frequent and severe weather events like hurricanes, droughts, and heatwaves. These changes disrupt ecosystems, affect agriculture, and pose risks to human health.

Efforts to mitigate global warming include reducing greenhouse gas emissions, transitioning to renewable energy sources like solar and wind, improving energy efficiency, and reforestation. International agreements like the Paris Agreement aim to limit global temperature rise and address the challenges of climate change.

It's crucial for countries, communities, and individuals to work together to combat global warming and its potentially devastating effects. This requires a combination of policy action, technological innovation, and changes in individual behavior and consumption patterns.