What Is Global Warming?
Imagine Earth wrapped in a cosy blanket. That blanket is our atmosphere – a layer of gases that surrounds the planet. Some of those gases, called greenhouse gases, trap heat from the Sun and keep our world warm enough for life. Without them, Earth would be a frozen, lifeless ball.
Global warming is the long-term rise in Earth’s average temperature. Think of it as that blanket getting thicker and thicker, trapping more and more heat. But why is that happening? To understand, we first need to know how the natural blanket works.
The Natural Greenhouse Effect
The Sun sends energy to Earth as light and heat. Some of this energy warms the ground, oceans, and air. The rest bounces back into space. Greenhouse gases act like a one-way mirror: they let sunlight in, but they stop some of the heat from escaping. This is called the natural greenhouse effect.
A simple analogy: a greenhouse for plants. The glass roof lets sunlight in to warm the plants and soil, but it prevents the warm air from leaving. Earth’s greenhouse gases do the same thing on a global scale. Without this effect, our planet would be about 30°C colder – far too cold for most life.
The Main Greenhouse Gases
The three most important greenhouse gases are:
- Carbon dioxide (CO₂) – released when we burn fossil fuels like coal, oil, and gas, and also from natural processes like volcanic eruptions and breathing.
- Methane (CH₄) – produced by livestock, rice paddies, and landfills. It is much more powerful than CO₂ at trapping heat, but there is less of it.
- Water vapour (H₂O) – the most abundant greenhouse gas. It acts as a natural feedback: as the air warms, it can hold more water vapour, which then traps more heat.
These gases are essential for life – we just need the right balance. But human activities are now adding extra greenhouse gases, making the blanket thicker. That’s what we call the enhanced greenhouse effect, which leads to global warming. (We’ll explore that in the next level!)
Key Takeaways
- Global warming is the long-term rise in Earth’s average temperature.
- The natural greenhouse effect keeps Earth warm by trapping some heat in the atmosphere.
- The main greenhouse gases are carbon dioxide, methane, and water vapour.
- Without the natural greenhouse effect, Earth would be too cold for life.