GEF

Unit 2  |  Humanity’s Ecological Footprint 44 Economic growth often comes with a price to the environment. Factories produce water and air pollution. Burning fossil fuels releases greenhouse gases (GHGs) such as carbon dioxide (CO 2 ) . Despite concerns about health and environmental effects, smog and other atmospheric pollutants have been considered an unfortunate, but necessary, byproduct of eco- nomic growth throughout much of the past two hundred years. 2.5  GREENHOUSE GASES AND CLIMATE CHANGE MEASUREMENT Economic growth and the human desire for modern conve- nience continue to drive industrialization around the globe. As a result, more natural resources are used, including the combustion of fossil fuels. This has led to humanity’s far- thest-reaching ecological footprint— climate change . This phenomenon is the large-scale alteration of the Earth’s climate. It has resulted in changes in long-term weather patterns and temperature of the planet. Earth’s atmosphere naturally has a greenhouse effect . Naturally occurring greenhouse gasses (GHG), such as carbon dioxide (CO 2 ) and methane (CH 4 ), trap the Earth’s heat and raise temperatures to a level in which life can thrive. Without the greenhouse effect, the average temperature of the earth would be about zero degrees F (-18°C) instead of its present 57°F (14°C). Greenhouse gas concentrations and the climate have changed greatly during Earth’s long history. The present concern is that burning fossil fuels is rapidly altering the climate by releasing more GHG than ecological systems can absorb. As a result, the average global temperature is increasing at a rapid rate. FOSSIL FUELS Natural fuels, such as coal or gas, formed in the geologi- cal past from the remains of living organisms. GREENHOUSE GASES Gases, including carbon dioxide, water vapor, and methane, that trap heat in the atmosphere. CARBON DIOXIDE (CO 2 ) Carbon dioxide, or CO 2 , is a gas that is the most common form of atmospheric carbon, used by plants in photosyn- thesis, and emitted during the combustion of carbon based fuels such as petroleum. SMOG A form of air pollution that results from the combination of industrial or vehicle emis- sions and sunlight. CLIMATE CHANGE Long-term statistical change in weather and temperature patterns. GREENHOUSE EFFECT The heating of the atmo- sphere due to the presence of carbon dioxide, methane, and other gases. ECOLOGICAL SYSTEMS Large-scale components of the Earth, such as the oceans, the atmosphere, and the biosphere.