Many chemical compounds found in the Earth’s atmosphere act as “greenhouse gases.” These gases allow sunlight to enter the atmosphere freely. When sunlight strikes the Earth’s surface, some of it is reflected back towards space as infrared radiation (heat). Greenhouse gases absorb this infrared radiation and trap the heat in the atmosphere. Over time, the amount of energy sent from the sun to the Earth’s surface should be about the same as the amount of energy radiated back into space, leaving the temperature of the Earth’s surface roughly constant. Greenhouse gases greatly affect the temperature of the Earth. Without them, Earth's surface would average about 33°C colder than the present average of 14 °C (57 °F). However, due to certain human activities, there is an increase in the amount of greenhouse gases causing the earth to “warm” but we will talk about that later.
EXAMPLES [SLIDE 4]
Many gases exhibit these “greenhouse” properties.In order, the most abundant greenhouse gases in Earth's atmosphere are: * water vapour (H2O) * carbon dioxide (CO2) * methane (CH4) * nitrous oxide (N2O) * ozone (O3)
And some are exclusively human-made like aerosols and halocarbons.
SOURCES [SLIDE 6]
There are three primary anthropogenic (human caused) contributors to rising greenhouse gas concentrations: (1) our excessive burning of fossil fuels for energy,
(2) our accelerating removal of the earth's natural carbon storage through our destruction of forests and our removal of previously vegetative land for habitat, grazing, and agriculture for livestock production and
(3) our various manufacturing processes which release near-permanent and extremely potent man-made greenhouse gases.
(4)Population growth is another factor in global warming, because as more people use fossil fuels for heat, transportation and manufacturing the level of greenhouse gases continues to increase. As more farming occurs to feed millions of new