Greenhouse Effects.
                     GREENHOUSE EFFECTS
Greenhouse effect
• The greenhouse effect is a natural process that warms the Earth’s surface. When 
the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to 
space and the rest is absorbed and re-radiated by greenhouse gases.
Source: www.environment.gov.au
How does the greenhouse effect work?
• A greenhouse stays warm inside, even during the winter. In the daytime, sunlight 
shines into the greenhouse and warms the plants and air inside. 
• At nighttime, it's colder outside, but the greenhouse stays pretty warm inside. 
That's because the glass walls of the greenhouse trap the Sun's heat.
Source: climatekids.nasa.gov
How are humans impacting the greenhouse effect?
• Human activities are changing Earth's natural greenhouse effect. Burning fossil 
fuels like coal and oil puts more carbon dioxide into our atmosphere.
Source: climatekids.nasa.gov
What reduces the greenhouse effect on Earth?
• Plants can help to balance the greenhouse effect on Earth. All plants from giant 
trees to tiny phytoplankton in the ocean take in carbon dioxide and give off oxygen.
Source: climatekids.nasa.gov
Which gases cause the greenhouse effect?
• In descending order, the gases that contribute most to the Earth’s greenhouse 
effect are:
– water vapour (H2O)
– carbon dioxide (CO2)
– nitrous oxide(N2O)
– methane (CH4)
– ozone (O3)
Source: www.bgs.ac.uk
Greenhouse Gases Effect on Global Warming
• The 'greenhouse effect' is the warming of climate that results when the 
atmosphere traps heat radiating from Earth toward space. 
• Certain gases in the atmosphere resemble glass in a greenhouse, allowing sunlight 
to pass into the 'greenhouse,' but blocking Earth's heat from escaping into space.
Source: www.bgs.ac.uk
Anthropogenic greenhouse gases
• Since the start of the Industrial Revolution in the mid-18th century, human 
activities have greatly increased the concentrations of greenhouse gases in the 
atmosphere. 
• Consequently, measured atmospheric concentrations of CO2 are many times 
higher than pre-industrial levels.
Source: www.bgs.ac.uk
MAIN SOURCES OF ANTHROPOGENIC GREENHOUSE 
GASES
Burning fossil fuels
• The burning of fossil fuels has elevated CO2 levels from an atmospheric 
concentration of approximately 280 parts per million (ppm) in pre-industrial times 
to over 400 ppm in 2018. This is a 40 per cent increase since the start of the 
Industrial Revolution.
Source: www.bgs.ac.uk
Land Use
• Agriculture, deforestation and other changes in land use account for one quarter of net 
anthropogenic greenhouse gas emissions.
• According to a United Nations report, livestock is responsible for about 14.5 per cent of this. The 
main sources of emissions are:
– feed production and processing (45 per cent)
– outputs of greenhouse gases during digestion by cows 
Source: www.bgs.ac.uk
Aerosols
• Aerosols are small particles suspended in the atmosphere that can be produced when we burn 
fossil fuels. 
• Other anthropogenic sources of aerosols include pollution from cars and factories, 
chlorofluorocarbons (CFCs) used in refrigeration systems and CFCs and halons used in fire 
suppression systems and manufacturing processes.
Source: www.bgs.ac.uk