9.2

• Greenhouse gases maintain temperatures on earth high enough to support life.
• Greenhouse gases include water vapour, CO2 & CH4.
• The greenhouse gas effect: electromagnetic radiation at most wavelengths (both long and short) from the sun passes through the Earth’s atmosphere.
• The Earth absorbs some radiation and thus warms up, which is essential for life on Earth.
• Some heat is radiated from the Earth as infrared radiation.
• Some of the infrared radiation is absorbed by greenhouse gases in the atmosphere.
• Atmosphere warms up leading to the greenhouse effect and global warming.
• Human activities which contribute to an increase in greenhouse gases in the atmosphere include activities that increase levels of CO2 & CH4.
• Examples of human activity that increase levels of CO2 include driving and consuming electricity.
• Examples of human activity that increase levels of CH4 include raising livestock, particularly cows, and the decay of organic waste in landfill sites.
• Based on peer-reviewed evidence, many scientists believe that human activities will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change.
• Global climate change: an increase in average global temperature is a major cause of climate change.
• Global climate change may lead to the extinction of species, raising sea levels due to the melting of polar ice caps, migration of people due to drought or flooding, and a decrease in crop yield for all major world crops.
• Carbon footprint: the total amount of CO2 and other greenhouse gases emitted over the full life cycle of a product, service or event.
• Carbon footprint can be reduced by reducing emissions of carbon dioxide and methane, for example, by using less electricity, reducing the amount of travel or transportation, and planting more trees.
• However, action may be limited because it’s more difficult, can be more expensive and planting trees takes away land that could be used to grow crops.