What is global warming?

Explanation

**Step-by-Step Solution:**

1. **Definition of Global Warming**: Global warming refers to the gradual increase in the Earth's surface temperature. This includes not just the land but also the oceans and the atmosphere.

2. **Causes of Global Warming**: The primary cause of global warming is human activities. These activities release greenhouse gases into the atmosphere.

3. **Human Activities Leading to Global Warming**:
- **Burning of Fossil Fuels**: This is one of the main activities contributing to global warming. When fossil fuels like coal, oil, and natural gas are burned for energy, they release carbon dioxide (CO2) and methane (CH4) into the atmosphere.
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