What is Weather?
The weather is all around us. The weather is sunny or rainy, cloudy or windy, snowing or stormy. The weather is what is happening outdoors in some place at a time or day.
What is Climate?
The climate describes what the weather is over many years at a place. For example, Melbourne has a cooler climate than Brisbane. Darwin has a humid climate and the climate around Alice Springs is hot and dry. The climate in Antarctica is pretty chilly!
The Changing Climate
We can look at the climate of the whole Earth over thousands or even millions of years. One thing that we find is that it is always changing. These changes usually happen very slowly — over hundreds or thousands of years.
One of the more important long term climate changes are ice ages. Ice ages usually happen every 10,000 to 20,000 years. During these periods ice covers a much larger part of the Earths surface than it does now and the Earth becomes much colder.
For example, on the map below the white areas show areas covered by ice during the last ice age about 20,000 years ago. It can be seen that much of Europe and North America were covered by ice.
Global Warming
Over the last hundred years or so the Earth has been slowly becoming more warm — and this seems to be speeding up. It doesn't seem much — less than 1oC warmer overall in the last 100 years. However it has scientists very worried. For example, in the Arctic it has warmed by up to 5oC and the ice is starting to melt away.
Scientists are worried because unlike other climate changes this warming may be man made. The warming may be caused by the pollution from our cars, factories, and power stations. This idea of why the Earth is warming are generally called the greenhouse effect.
If correct, then these changes may occur faster and faster and cause massive problems for the Earth within a lifetime.
There is no doubt that the Earth has become warmer, however there is still some argument among scientists about exactly what is causing it. Most scientists think that it is likely to be man made and due to the greenhouse effect.