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• An increase in greenhouse gases in the atmosphere is causing the planet to increase in temperature. This is causing climate change.
• The effects of climate change include rising sea levels, more extreme weather and more forest fires.

Thermal energy (heat energy) radiates from the Sun. Some of this hits the Earth. Without this, there would be little or no life on Earth. Not all of the thermal energy that hits the Earth stays here. Some of it is reflected off pale, shiny surfaces like ice and escapes into space.

Some gases in the atmosphere, called greenhouse gases, trap escaping thermal energy. This causes some of the thermal energy to return to the surface and warm it up. This is called the greenhouse effect. It is much hotter standing in a greenhouse or sitting in a car with the windows up on a sunny day than a cloudy one for the same reason. As there are more greenhouse gases in the atmosphere, the Earth is getting hotter.

Humans burn fossil fuels to generate electricity, to keep buildings warm, and to power cars and other machines. Waste gases are released during this combustion, including carbon dioxide. As the human population has increased more fuel is used and more carbon dioxide is released.

The amount of carbon that our activities release is called our carbon footprint. Some activities are described as carbon neutral. These add no extra carbon dioxide to the atmosphere and have no effect on our carbon footprint. For example, walking or cycling to school is carbon neutral.

Other activities store carbon and so reduce it from the atmosphere. This also decreases your carbon footprint. Planting trees or other plants is an important way to remove carbon from the atmosphere.

Extra carbon dioxide in the atmosphere increases the greenhouse effect. More thermal energy is trapped by the atmosphere, causing the planet to become warmer than it would be naturally. This increase in the Earth's temperature is called global warming.

Climate scientists now agree that the increasing levels of carbon dioxide and other greenhouse gases are directly linked to the increasing global temperatures. Global warming is having an effect on the world's climates. This is called climate change.

The weather includes the wind, sunshine and rain you see from day to day. The climate is the weather seen over years and decades. Climate change and its effects as a result of global warming include:

• Ice on land melting faster than it can be replaced in the Arctic and Antarctic, causing sea levels to rise.
• Oceans warming up, which affects corals as they bleach and then die.
• Extreme weather events like flooding and heat waves, cold snaps and violent storms.
• Increases in the number and strength of forest fires.
• Changes to the places where animals and plants live, making their survival harder.
• More tropical diseases spreading to new places as insects fly to new homes.

There are things we can do to help stop climate change.

• When other options are available, don't travel by aeroplane or car, especially petrol and diesel cars.
• Walk, cycle or use public transport.
• Eat less meat - animals release a lot of methane, especially cows and pigs.
• Reduce, reuse and recycle waste.
• Support sustainable companies, which do not pollute as much as other companies.
• Wear more clothes and heat our homes less.
• Turn off electrical appliances when we are not using them.
• Plant trees.
• Use 'green' electricity from solar panels and wind turbines.
• Buy second-hand clothes, electronics and furniture instead of new ones.