The Greenhouse Effect

Review Previously, we learned that the sun emits energy that travels to Earth The sun’s energy is either reflected or absorbed Some parts of our atmosphere absorb the suns energy

The Role of the Climate System Without Earth’s climate system, the planet would be much colder than it is now. The climate system helps to maintain Earth’s temperature by trapping and storing energy from the Sun and spreading it around the world. Greenhouse Effect: a natural process whereby gases and clouds absorb infrared radiation emitted from the Earth’s surface and radiates it, heating the atmosphere and Earth’s surface.

What is the Greenhouse Effect? The atmosphere allows radiation (higher-energy) from the Sun to pass through Radiation is absorbed by the Earth’s surface This energy becomes thermal energy and warms the surface The surface emits infrared radiation Gases in the atmosphere trap much of the IR radiation, radiating the energy in all directions, sending some back to the surface This warms the surface even more

Non Greenhouse Gases Most of the air is made up of nitrogen and oxygen gases These gases do not absorb radiation from the Earth’s surface

Greenhouse Gases Water vapour (H2O) – most important The greenhouse effect is caused by gases that make up a small portion of the atmosphere, known as the greenhouse gases Water vapour (H2O) – most important Carbon dioxide (CO2) Methane (CH4) Nitrous oxide (N2O) Their contribution to the greenhouse effect is determined by their concentration and by how much thermal energy each molecule can absorb

Carbon Dioxide Concentration in atmosphere: 0.0385% or 385 parts per million (ppm) Estimated to cause up to a quarter of the natural greenhouse effect Concentration before the Industrial Revolution: 280 parts per million Natural sources of CO2 include: volcanic eruptions, burning of organic matter and cellular respiration

Water Vapour Warmer temperatures mean more water in the atmosphere About two-thirds of the greenhouse effect is caused by water vapour Quantity of water vapour in the atmosphere depends on the temperature of the atmosphere Warmer temperatures mean more water in the atmosphere Colder temperatures mean less water in the atmosphere

Methane Methane is 23 times more powerful of a greenhouse gas than CO2 Much less methane than carbon dioxide in the atmosphere Methane can hold much more thermal energy than carbon dioxide Methane is 23 times more powerful of a greenhouse gas than CO2 Produced naturally from plant decomposition in swamps and animal digestion, but also human sources Concentration before the Industrial Revolution: 0.700 parts per million It is now 1.785 ppm

Nitrous Oxide A Molecule of N2O is almost 300 times more effective than a molecule of CO2 It is less available than CO2 though Concentration before the Industrial Revolution: 0.270 parts per million Risen to 0.321 ppm Produced both naturally and by human sources Naturally through reactions of bacteria in soil and water

The Anthropogenic Greenhouse Effect

The Anthropogenic Greenhouse Effect Anthropogenic: resulting from a human influence If we continue to produce greenhouse gases at a similar rate, Earth’s average temperature will likely increase by 2°C to 6°C by the end of the century. May not sound like much, but can cause dramatic impacts on species survival, habitability, and weather conditions

Anthropogenic Sources of Greenhouse Gases Carbon Dioxide: burning fossil fuels (transportation, heating, electricity and industry) and deforestation  Methane: agricultural activities (rice farming, cattle ranching), decay of organic materials in landfills and sewage treatment, coal mining and natural gas extraction Nitrous Oxide: management of livestock feed and waste, farming using nitrogen fertilizer, industrial processes

Our Own Doing!!! Chloroflourocarbons (CFCs) - There are no natural sources of CFCs. Leak out from refrigerators, air conditioners and through other industrial processes