Global warming is the idea that the earth is warming up because of humans and leading to a change in climate worldwide. We are contributing to it by putting too many greenhouse gases like carbon dioxide (CO₂) into the earth’s atmosphere and increasing the greenhouse effect.

What is the ‘greenhouse effect’?

It’s a natural process. In fact, if the greenhouse effect didn’t exist, neither would we! The atmosphere around the planet acts like a blanket, or ‘greenhouse’, to keep some of the energy from the sun inside the atmosphere so it doesn’t all escape back out into space. This energy is captured by greenhouse gases in the atmosphere. Without this effect, the earth would be too cold and we wouldn’t be able to live here! As well as keeping us warm, the atmosphere also protects us from some of the harmful regions of the electromagnetic radiation the sun produces.

 

What are greenhouse gases?

Their names are carbon dioxide (CO₂), nitrous oxide (N­₂O), methane (CH₄), ozone (O₃) and water vapour (H₂O), and they are important because they absorb infra-red radiation that is emitted from the earth’s surface before it gets back out into space. This infra-red radiation creates heat and so keeping this radiation inside the atmosphere keeps the earth warm.

 

What is the problem?

Unfortunately, humans are increasing the amount of greenhouse gases, particularly carbon dioxide, in the atmosphere through our activities. Because there are now more molecules to absorb the infra-red radiation, more of it is absorbed and more heat is kept inside the atmosphere. This is causing the earth to warm up much more than it used to.

The earth has come up with a clever, natural way to get rid of some of the carbon dioxide from the air. The oceans can dissolve carbon dioxide, removing it from the air, and this keeps a natural balance around the earth and in the atmosphere.  However, humans are adding too much extra carbon dioxide into the atmosphere, and this natural process can’t keep up. This is why the earth is heating up.

There is the possibility that the capacity of the oceans for removing carbon dioxide will never match the amount we need removed, and if it does, the high concentrations of carbon dioxide dissolved in the water will greatly affect the way that other natural processes occur. For example, dissolving carbon dioxide in water makes it more acidic, and many natural reactions and organisms are sensitive to acidic conditions.

What are humans doing?

We are using fossil fuels to run our cars, produce electricity and generally fuel our energy intensive lives. Fossil fuels are carbon-rich and to produce energy they are burned in oxygen. This chemical reaction is called combustion and produces energy but also produces a lot of carbon dioxide gas that gets released into the atmosphere as an unwanted product.

This isn’t something that scientists have just discovered.

The concept of ‘global warming’ was actually predicted by a Swedish scientist called Svante Arrhenius, well over 100 years ago!

“Doubling CO₂ in the atmosphere by burning coal will cause a 5-6°C rise in Earth’s temperature”
Svante Arrhenius, 1896

Have a look at the ‘Fossil Fuels’ page to discover more!