The Earth is very old. It has changed often during its long life, and it is still changing. Millions of years ago, when dinosaurs like Tyrannosaurus rex were alive, the Earth was much warmer. There was very little ice on the land or on the sea, even in the very north or the very south of the world. And the sea was much higher than it is today.
There have been many changes since that time, sometimes to a warmer climate, sometimes to a colder one. About 20,000 years ago, for example, a time called an Ice Age began. There was ice over much of the world, and it was 3 kilometres deep over much of North America and Europe. And the sea was not as high as it is today. Our climate has changed many times, and it will change again.
But now, for the very first time, people are changing the climate. In the year 1900, the Earth was 0.7 C colder than it was in 2000, just one hundred years later. This change did not happen because of the Earth’s orbit – it happened because of us. Some people think that this is a small change. But think about this. A change of just 5 to 7 C can start or finish an Ice Age.
Can the climate change like this? Scientists think that it can – but not as quickly as this. Scientists do not always agree. Some think that the climate is changing a lot, and some think that it is changing a little. Some think that it will change quickly, and some slowly. But all scientists agree that climate change is happening. The important question is this: how dangerous will the change be?
Al Gore, who worked next to President Clinton of the USA between 1993 and 2001, thinks that the change will be dangerous. In his film An Inconvenient Truth, Al Gore describes how the Earth’s climate has changed. He has talked about the dangers of climate change for more than twenty years, but is he right? Is climate change a dangerous problem? Must we do something about it? And what can we do?