Climate change - what is it?
Greehouse effect
A greenhouse works by trapping heat from the sun. Its glass panels let in the sunlight, which warms plants, soil, and other objects inside the building. The panels also keep the produced heat from escaping - and the temperature in the greenhouse rises.
A similar phenomenon takes place in the Earth's atmosphere as a natural and necessary process. Heat-trapping greenhouse gases, such as carbon dioxide, work somewhat like glass panels, preventing heat from escaping to space. The greenhouse effect warms the planet to support life. Without it, the temperature on the Earth's surface would be more than 30 ºC (86 ºF) colder than it is now.
Human activities have caused a significant increase of greenhouse gases in the atmosphere. The gases enhance the effect and warm the globe. This warming and its consequences are referred to as climate change.
Rapid changes are taking place
The Intergovernmental Panel on Climate Change (IPCC) is a UN body which brings together hundreds of climate experts from across the world. It reports that the Earth's average temperature has increased globally by 0.74º C (33.33º F) over the past 100 years. In fact, the 20th century was the warmest century and the 1990s were the warmest decade in the past 1,000 years. It has been projected that, by the year 2100, the temperature is likely to increase even by 4ºC (39.2º F) unless the wold takes action to limit greenhouse gas emissions.
These changes in temperature might not seem very significant. But comparing them to the last Ice Age brings them into new light. During the Ice Age the average global temperature was only 5°C (41º F) lower than the current temperature. At that time most of Europe and North America were covered by a thick layer of ice.
Why is this happening?
The changes in the Earth's temperature are in part natural. Climate has, and always will, vary for different reasons, such as volcanic eruptions and the amount of energy released from the Sun.
However, enhanced warming has occurred due to industrial and agricultural activities since the industrial revolution in the 18th century. Greenhouse gases are emitted into the atmosphere. They absorb the heat produced by the sunlight and acellerate the greenhouse effect. Carbon dioxide accounts for over 80 % of the emissions. It is released mainly by fossil fuel burning, particularly in energy production and transport, and deforestation. Other greenhouse gases are released by certain industrial activities, agriculture and waste dumps.