Climate change explained

The Earth’s climate is driven by a continuous flow of energy from the sun.

Energy in the form of heat, from the sun, passes through the Earth’s atmosphere and warms the Earth’s surface.

As the temperature increases, the Earth sends heat energy (infrared radiation) back into the atmosphere.

Some of this heat is absorbed by gases in the atmosphere, such as carbon dioxide (CO2) , water vapour, methane, nitrous oxide, ozone and halocarbons.
 

Watch this video from National Geographic for a short visual explanation of climate change.



 

The Greenhouse Effect / ©: IPCC
The Greenhouse Effect. (click for bigger version)
© IPCC

The greenhouse effect

These gases, which are all naturally occurring, act as a blanket, trapping in the heat and preventing it from being reflected too far from the Earth. They keep the Earth's average temperature at about 15°C: warm enough to sustain life for humans, plants and animals. Without these gases, the average temperature would be about -18°C... too cold for most life forms. This natural warming effect is also sometimes called the greenhouse effect.

CO2?

Carbon dioxide, or CO2, is the most significant of the gases in our atmosphere which keep the Earth warm.

4 billion years ago its concentration in the atmosphere was much higher than today - 80% compared to today's 0.03%. But most of it was removed through photosynthesis over time. All this carbon dioxide became locked in organisms and then minerals such as oil, coal and petroleum inside the Earth's crust.

A natural carbon dioxide cycle keeps the amount of CO2 in our atmosphere in balance. Decaying plants, volcanic eruptions and the respiration of animals release natural CO2 into the atmosphere, where it stays for about 100 years. It is removed again from the atmosphere by photosynthesis in plants and by dissolution in water (for instance in the oceans).

The amount of naturally produced CO2 is almost perfectly balanced by the amount naturally removed. But even small changes caused by human activities can have a significant impact on this balance.

Climate Change or Global Warming?

  • The terms "climate change" and "global warming" are often used interchangeably.

    Generally WWF use the more scientifically accurate term "climate change", but we often use "global warming" as it remains popular in public discourse.

    This definition from the NASA website is perhaps the best way to approach the two labels.

    "Global warming refers to surface temperature increases, while climate change includes global warming and everything else that increasing greenhouse gas amounts will affect."

    NASA: What's in a Name? Global Warming vs. Climate Change

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  • Seize Your Power / ©: Global Warming Images / WWF-Canon

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