No environmental issue has sparked more controversy in the last decade than the issue of Climate Change or Global Warming. The heat of the debate is not matched by knowledge about the subject. As a result, I am going to write about the topic—in several pieces in order to emphasize that the topic has a number of moving parts that all deserve thoughtful discussion.
I find it useful to start the conversation with the following questions:
1. What air pollutants are regulated by the EPA under the Clean Air Act (CAA)?
2. What are “greenhouse gases” (GHGs).
3. What is the significance of GHGs?
4. Where do GHGs come from?
EPA, under the CAA, has regulated what have commonly been referred to as “conventional pollutants.” These are:
–Carbon Monoxide (CO)
–Sulfur Dioxide (SO2)
–Nitrogen Dioxide (NO2)
To varying degrees, EPA regulates both “stationary sources” (e.g., manufacturing facilities) and mobile sources (e.g., automobiles) that generate conventional pollutants.
EPA’s historic position was that it did not have authority under the CAA to regulate what have come to be referred to as GHGs. Several states, including the state of Massachusetts, sued EPA seeking to require it to regulate GHGs, and, in 2007, the United States Supreme Court (Massachusetts, et al, Petitioners v. Environmental Protection Agency, et al) ruled in favor of petitioners and against EPA. [The decision was rendered by a 5-4 vote with several dissents.] The Court concluded that GHGs are air pollutants and that the EPA is obligated to regulate them.
So, what are GHGs; where do they come from; why are they important; and what, if anything, can be done about them? These are big, and important, questions.
GHGs are generally considered to consist of the following:
–Carbon Dioxide (CO2)
–Nitrous Oxide (N2O)
Earth is unusual in that it contains tremendous amounts of water; in fact, approximately 70% of the Earth’s surface is occupied by water. For this reason, Earth is commonly referred to as the “Water Planet.” Water is essential for life, but so is heat.
GHGs are critical because they are responsible for retaining temperatures that allow the existence of life forms on Earth.
Earth is also located in relation to its sun so that its water supply is not consumed by the Sun’s heat. Earth receives energy from the Sun via relatively short radiation waves and, in turn, emits energy via relatively long radiation waves. GHGs both emit and absorb the longer wavelength radiant energy emitted from the Earth’s surface. The absorption of the long wave radiation by GHGs warms the atmosphere. The emission of long wave radiation from GHGs downward to Earth is the “greenhouse effect.” Thus, the more GHGs in the atmosphere, the greater the Earth’s temperature.
Some GHGs are naturally generated; and some are generated by what are called anthropological activities—i.e., human activities. As stated above, 70% of Earth is covered by water. It should, therefore, come as no surprise that water vapor constitutes 70% of all GHGs. Carbon Dioxide constitutes 15% of GHGs; Methane constitutes 8%; and, combined, Nitrous Oxides, Hydrofluorocarbons, Sulfur Hexafluoride and Perfluorocarbons constitute 7%.
The political debate about Climate Change tends to revolve around Carbon Dioxide because it constitutes 72% of all anthropological sources of GHGs (even though CO2 constitutes only 15% of all GHGs). A number of activities generate Carbon Dioxide including:
–Wind exchange with salt water
–Animal and plant respiration
–Fossil fuel combustion,
–Direct releases from soil and
–Natural activities such as volcanoes, hot springs and geysers
Man-made contributions of CO2 are: power stations (29.3%), industrial processes (20.6%), transportation fuels (19.2%), residential and commercial sources (12.9%), land use and biomass burning (9.1%) and mining processing and distribution (8.4%).
A similar analysis can be done with respect to methane (which constitutes 18% of man-made GHG emissions) and nitrous oxides (which constitute 9% of man-made GHG emissions); however, to summarize, most methane emissions are attributed to fossil fuel mining and agriculture (49.6%) and most nitrous oxide emissions are attributed to agriculture (62%).
In my next post, I am going to get into issues relating to the amount of CO2 in the atmosphere, how it has changed over time and the significance of current and expected levels.