Green House Gases and Climate Change relates to conditions in the upper atmosphere, and the resulting effects of the earth’s temperature.
The greenhouse effect is the term used to describe the role of the atmosphere in insulating the planet from heat loss. Greenhouse gases (GHG) are gases in the atmosphere that give rise to this greenhouse effect. GHGs allow shortwave or solar radiation to penetrate down to the atmosphere and the Earth’s surface. This radiation is absorbed and the Earth’s surface warms. GHGs function as a blanket that traps heat in the lower atmosphere – termed the “greenhouse effect.”
This “natural greenhouse effect” is an important phenomenon to biological life on Earth. The average surface temperature is maintained at approximately 15°C because of this effect. Without GHGs, the Earth’s average temperature would be about 33°C lower than it is, making the climate too cold to support life (Schneider, 1989). Naturally occurring GHGs include water vapour, ozone, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O).
While these naturally occurring gases are what make life possible, a serious concern today is the increasing levels of some of these gases in the atmosphere. Human activities such as the burning of fossil fuels, deforestation, industrial processes, etc., are increasing the concentration of GHGs in the atmosphere at an alarming rate, causing Climate Change. This can have serious impacts on the physical and chemical processes, and biological life on Earth.
It is estimated that the Earth’s average temperature has risen by 0.6°C since 1880 because of emissions of greenhouse gases from human activity. The atmospheric concentration of CO2 has increased by 31 % since 1750 and continues to increase, on average, by 1.5 ppm or 0.4 % per year. The atmospheric concentrations of CH4 and N2O have increased by 151 % and 17 %, respectively, since 1750.
The main sources of these emissions, particularly carbon dioxide, methane and nitrous oxide, are do to the combustion of large amounts of fossil fuels (producing CO2), and deforestation (less trees mean that less CO2 is being absorbed and stored).
How does Air Quality differ from Climate Change and Green House Gases?
Air Quality issues primarily affect the lowest part of the atmosphere, which is also the zone of air we breathe, and usually refers to the amount of particulate matter that is the air. Particulate matter (PM) consists of airborne particles in solid or liquid form. PM may be classified as primary or secondary, depending on the compounds and processes involved during its formation.
Primary PM is emitted at the emissions source in particle form, for example, the smokestack of an electrical power plant or a recently tilled field subject to wind erosion. Secondary PM formation results from a series of chemical and physical reactions involving different precursor gases, such as sulphur and nitrogen oxides, and ammonia reacting to form sulphate, nitrate and ammonium particulate matter.
The size of PM particles largely determines the extent of environmental and health damage caused. For this reason, Environment Canada identifies different sizes of PM: Total Particulate Matter (TPM) – airborne particulate matter with an upper size limit of approximately 100 micro metre (µm) in aerodynamic equivalent diameter Particulate Matter <10 microns (PM10) – airborne particulate matter with a mass median diameter less than 10 µm Particulate Matter < 2.5 microns (PM2.5) - airborne particulate matter with a mass median diameter less than 2.5 µm.
Air Quality also deals with the direct health effects associated with breathing in these particulate materials. Numerous studies have linked PM to aggravated cardiac and respiratory diseases such as asthma, bronchitis and emphysema and to various forms of heart disease. PM can also have adverse effects on vegetation and structures, and contributes to visibility deterioration and regional haze/smog.