Level: Primary

Old weather records
There are many, very old weather records that scientists use to see what the weather was like a long time ago. But not all – especially those about 300 years old – contain all the information they should.

Also, in the past, the instruments that recorded the weather were too expensive for most people and did not work very well. But, fairly accurate measurements of temperature, rainfall and air pressure have now been possible for a long time.

All of these weather records are now being used to see what the weather and climate has been like for the past few hundred years.

What do the weather and climate records tell us?
The old weather records show that we are now seeing much higher temperatures. Also, temperatures during the past 30 years are getting much warmer, much faster than we have seen for a very long time.

However, some of these changes could be caused by other things.

As villages become small towns and continue to grow, weather records (especially temperatures) are going to be affected by all the new houses.
The instruments that measure the weather are sometimes moved to other places.
The equipment used to record the weather now has become more accurate.
All of this can make a big difference to how scientists use the information.

What is causing global warming?
A major cause of global warming is known as the ‘Greenhouse Effect’. In a greenhouse the temperature inside begins to rise above the temperature outside when the sun shines on it. This is because the sun’s heat gets trapped inside.

In the air, there are several gases that do the same thing as the glass in the greenhouse. The three ‘greenhouse’ gases that do this the most are called water vapour, methane and carbon dioxide.

While humans don’t create much water vapour in the air, we do make methane and carbon dioxide. Methane comes from several places, including agriculture (livestock), wetlands and landfill sites, and is a very powerful greenhouse gas.

When humans burn forests, oil and gas, it also makes huge amounts of carbon dioxide. In terms of global warming, carbon dioxide is the most important greenhouse gas.

Over the past 50 years, scientists have measured a steady increase in the amount of carbon dioxide in the air. This extra carbon dioxide has been shown to help warm up the whole Earth.

In fact, since the Industrial Revolution started around 200 years ago, the amount of carbon dioxide in the air has increased by 30% – mostly due to human activities.

The amounts of two other important greenhouse gases in the air, methane and nitrous oxide, are also increasing.

In fact, we now have more carbon dioxide and methane in the air than the earth has seen for at least 650,000 years.

Can anything be done about climate change?
There is more and more evidence that human beings are the main cause of the increase in two main greenhouse gases in the air; methane and carbon dioxide. Farming and wetlands are some of the biggest sources of methane. The burning of fossil fuels (like coal and gas), cement production and the burning of forests by humans is the biggest cause of the increase in carbon dioxide in the air.

On current scientific evidence, ‘global warming’ could be slowed if the amount of greenhouse gases in the air were reduced.

You can play your part. Perhaps use the bus or try to walk to school, instead of using a car. Changing to the energy saving light bulbs is also a good idea, as they use only 20% of the electricity used by a normal light bulb. And recycling as much as possible can save huge amounts of energy.

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