This causes an increase in the heat of the lower atmospheric layer , the troposphere. Some of these radiations eventually find their way out to space but some reach the crust, making it hotter than it would be . Gases that contribute to the greenhouse effect are carbon dioxide, methane, ozone chlorofluorocarbons and nitrous oxide. While they have always been present in the atmosphere , their levels have been rising over the last 150 years due to human activity. Other factors, such as deforestation, also have an impact on climate .
Tropical forests absorb much of carbon dioxide that is released in the atmosphere.
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