Climate change is not new for our 4.5 billion years old home. It has been happening. But back then, climate change occured rather slowly, within a span of thousands of years. Today, it is different. Constantly growing human activities is why.
The Earth has always keeps its own greenhouse gases, so called natural greenhouse, however, human activities are changing the natural greenhouse. Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2). This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO2. To a lesser extent, the clearing of land for agriculture, industry, and other human activities has increased concentrations of greenhouse gases.
The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels from 280 parts per million to 400 parts per million in the last 150 years. The main impact was the increase in the global temperature of the planet, which has risen 1.1°C since this period, although it is estimated that, by the end of the present Century, the thermometer could rise by 2.7 °C even if national commitments to reduce emissions are fulfilled.