Causes of the Greenhouse Effect1 Energy from the Sun

beats down on the Earth.

2 Some energy is reflected into space, the rest enters the atmosphere.

3 The Earth absorbs the energy and emits heat.

4 Unlike other gases, greenhouse gases absorb and re-emit the heat energy - some is emitted into space and some back to Earth.

5 The heat is effectively trapped and warms the Earth.

Carbon Dioxide• Carbon dioxide (CO2) is

produced naturally through breathing or respiration, decay of plant and animal matter, and from natural forest fires.

• Man-made sources of carbon dioxide include the burning (or combustion) of fossil fuels, changes in land-use (especially deforestation), biomass burning and the manufacture of cement.

• Carbon dioxide is taken out of the atmosphere by the oceans, and by plants, especially forests, through photosynthesis.

Deforestation at work

Rainforest clearance & Global Warming 1. Clearing and burning rainforests release vast amounts of greenhouse

gases such as carbon dioxide, methane, ozone, and nitrous oxide into the atmosphere.

2. Each year deforestation contributes 23-30 percent of all carbon dioxide in the atmosphere.

3. Carbon dioxide, in turn, is believed to be responsible for approximately half of global warming.

4. At present, the countries emitting the most carbon into the atmosphere from tropical deforestation are, in order of importance, Brazil, Indonesia, Burma, Mexico and Thailand.

5. Tropical deforestation also leads to global warming by destroying one of the Earth's only ways to absorb excess atmospheric carbon.

6. Through photosynthesis, forests absorb and store so much atmospheric carbon that scientists refer to tropical rainforests as "carbon sinks".

7. Thus, while more and more carbon is released into the atmosphere, there are less and less forests to remove the carbon from the atmosphere.

8. Deforestation both releases huge amounts of carbon into the atmosphere and destroys our means of absorbing and storing this substance.

9. And it is not only carbon that is released. Rainforest canopies absorb nitrous oxide and ozone, which are released through deforestation.

Causes of an Accelerated

Greenhouse Effect

The graph below shows how the global temperature has changed over the last 130 thousand years. Between 20,000 years ago and the present, the Earth warmed by as much as 6°C. Scientists see it in tree rings, ancient coral and bubbles trapped in ice cores

What is the problem?

When a forest is cut and burned to establish cropland and pastures, the carbon that was stored in the tree trunks (wood is about 50% carbon) joins with oxygen and is released into the atmosphere as CO2.

From 1850 to 1990, deforestation worldwide (including the United States) released 122 billion metric tons of carbon into the atmosphere, with the current rate being approximately 1.6 billion metric tons per year. In comparison, fossil fuel burning (coal, oil, and gas) releases about 6 billion metric tons per year, so it is clear that deforestation makes a significant contribution to the increasing CO2 in the atmosphere.