Why is the Earth's climate change a cause for concern?

The Earth's climate has been changing for billions of years. It has warmed and cooled many times long before humans were around.The orgin of Man can be traced in the warm, relatively benign climate of equatorial Africa, but our ancestors battled the cold, harsh and unforgiving climate of the last Ice Age in order to spread across the planet. Some 10,000 years ago, however, the Ice Age ended. We developed agriculture, civilization, industry and technology generally in a global climate that was warm, pleasant and mostly predictable.

Today, people are concerned because the Earth is warming faster now than it has ever done in the past. This warming can threaten our existence.