The Earth's climate
Today, the Earth's climate has a huge effect on the daily lives of all the people in the world. It has always had a big effect on life on Earth, and it had a big effect on how life started billions of years ago.
So, what is climate? Climate is the usual weather in a place over a long time - normally thirty years or more. Weather can change quickly, and a place can have very different weather from one day to the next. But climate is those weather patterns over a long time.
On Earth, lots of things have an effect on the climate - the atmosphere, the oceans, the land, ice, people, plants and animals, and the light and heat from the Sun.
The Earth's atmosphere is a thin layer of gases above the Earth.
The Earth's atmosphere
Most of the atmosphere is nitrogen (N2) and oxygen (O2), but there are other gases in the atmosphere, too.
Some of the gases in the atmosphere are called greenhouse gases because, like the glass in a greenhouse, they keep the Earth warm. They do this by stopping some of the Sun's heat from leaving the Earth. They are very important because they help to keep the Earth at the right temperature for life to grow - not too hot and not too cold. Carbon dioxide (CO2) is a very important greenhouse gas. Without the greenhouse gases, the Earth would be very, very cold.
Many scientists study the Earth's atmosphere. They do this from satellites and from the land, and their studies show that the amount of greenhouse gases in the atmosphere is growing. This is making the temperature on Earth get warmer, and this warming is having a big effect on the climate.
We are already seeing the effects of this all over the world. Weather patterns are changing; the water in the oceans is getting warner; snow and ice are melting in the Arctic and Antarctica; and sea levels are increasing.