Stratospheric "Brightening" Theory
Just like washing a car or a pile of dirty dishes, our world has also been cleaned up from its recent past. Before the Clean Air Act, the world was a dirty place to live in, by far. Sulfate (SO4) aerosols, Nitrous oxide (NOx), and soot filled the atmosphere - polluting rivers, lakes, and entire cities. Even today, the affects of an unclean world can be seen in some cities such as Beijing, with heavy smog fills the air, darkening the air and polluting streams. Before 1970, large amounts of smog had filled the stratosphere, darkening the skies above.
However, at that time, the smog was counteracting the affects of global warming. Without the smog, the atmosphere would be a lot warmer today, and would have caused the atmosphere to rise an additional 0.4 degrees Celsius (0.72 degrees Fahrenheit) in temperature. However, gases such as SO4 and NOx in the stratosphere were reflecting the sun's heat back into space before they reached the greenhouse gases below them - therefore stabilizing the earth's temperature at 60 degrees Fahrenheit - the "normal temperature" of the earth.
The Clean Air Act, however, aimed to help the earth's environment by eliminating smog, may have had unforeseen consequences. The act was put forth to eliminate six primary pollutants, SO4 and NOx being two of them, from industry processes, commercial applications and car exhaust. Fortunately, the program was a success, and our world had become much more clean and free of smog. As one can see today, smog has been reduced by up to around 70% since the program's inception. However, since 1977 when the program had gone into full effect, global temperatures also began to rise - at an unprecedented rate of 0.2 degrees C (0.37 degrees F) per decade - the highest seen in much of recorded history.
The theory is that smog (in gray) in the upper stratosphere was shielding the earth from heat from the sun in the form of IR (infrared) radiation before 1977 when the increase began. This smog, in turn, had caused the stratosphere to warm as IR radiation was also scattered and trapped between these highly-reflective particles. As the stratosphere reflected the heat - the troposphere was shielded and had remained cool. However, today, as most pollutants have been removed from the atmosphere, this IR radiation reaches the troposphere - where it is trapped by increasing amounts of CO2 gas(in pink). This is causing what we know today as the phenomenon of global warming.
Of course, this is only in the stratosphere - as total visible light from the sun that hits the surface has decreased 22% in the past 35 years, the amount of light that passes through the stratosphere above it has doubled. Because of this, there are observably higher temperatures in the troposphere and reduced sunlight amounts - CO2 absorbs both light and heat from the sun. However, since there is less SO4 and NOX in the atmosphere today, the stratosphere has brightened in return - hence the name for the stratospheric "brightening" theory behind it.
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Trends in Global Temperature
Certain events in history coincided with the rise of global temperatures, some of which dealt with the elimination of smog such as the Clean Air Act and the Kyoto protocol.
*This site does not make allegations that the Clean Air Act was responsible to global warming. However, we would like to point out certain events in the history of the Clean Air Act in regards to the history of global temperature.
A – Air Pollution Control Act of 1955
- 1st federal air pollution law
- Identified air pollution as a national problem
- Mandated federal research programs to investigate health and welfare effects of air pollution
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B – Clean Air Act of 1970
“The amendments in 1970 were an entirely rewritten version of the original Clean Air Act. In principle, it was a law that would show excellent results; however, in the midst of environmental enthusiasm throughout the country, the Clean Air Act proved to be a highly ambitious piece of air pollution abatement legislation. It set National Ambient Air Quality Standards (NAAQS), to protect public health and welfare, and New Source Performance Standards (NSPS), that strictly regulated emissions of a new source entering an area. Standards were also set for hazardous emissions and emissions from motor vehicles. Funds of $30 million went toward research on the growing problem of noise pollution in larger cities. Also, as a new principle, this Clean Air Act allowed citizens the right to take legal action against anyone or any organization, including the government, who is in violation of the emissions standards.”
As it did address air pollution as a problem in the US, action by the government to limit pollution only took affect after 1977, right when global temperatures increased.
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C – 1st Deadline on Clean Air Act of 1970
“States are required to plan to meet the standards by 1975.”
However, states did not meet them until 1977…
D – Amendments to the Clean Air Act of 1970
Since states were not meeting the mandated standards put forth by the Clean Air Act of 1970, a new set of amendments were written in 1977 to, in essence, fill in the "holes" that allowed industries to pollute. For instance, the "grandfather" clause allowed older factories to continue polluting as they were not under the Clean Air Act of 1970. However, that all changed in 1977 where lawmakers presented legislation that restricted pollution from all industries, old and new alike.
"I am extremely pleased that the long struggle over the Clean Air Act is over.” - Douglas M. Costle
“The U.S. Environmental Protection Agency has issued final rules required under the Clean Air Act Amendments of 1977, which limit increases of air pollution in clean air areas of the country.”
Six criteria pollutants (particulate matter, sulfur dioxide, carbon monoxide, nitrogen oxides, ozone and lead) are addressed and industries are required to meet the standards set by the Clean Air Act of 1970, seven years after it was passed.
This, coincidentally, began the start of global temperature increase.
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E – Amendments to the Clean Air Act in 1985
F – Amendments to the Clean Air Act in 1990
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(also the eruption of Mt. Pinatubo in 1991 - a large volcano that released over 9 million tons of SO4 during eruption - thus stabilizing the global temperature for two years)
"An Act to amend the Clean Air Act to provide for attainment and maintenance of health protective national ambient air quality standards, and for other purposes."
“After a decade of virtual dormancy, Congress finally drastically amended the Clean Air Act again to attempt to solve problems of the past as well as deal with new issues.”
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G – Amendments to the Clean Air Act in 1997
H – Amendments to the Clean Air Act in 2000
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The Stratosphere
>>Hover over the picture to find out why the stratosphere was undergoing such dramatic temperature changes in the past 30 years.
CO2 emissions, most commonly from cars, industry and other commercial processes account for the rise in CO2 levels in the past 55 years. However, the rise in CO2 levels does not match the rise in global temperature, nor account for the breaks in the increase between 1977 and 2003. As one can see here, as global warming did not start until 1977, CO2 levels had already risen significantly by that time, indicating that CO2 might not be the cause.
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References
United States Geological Survey, Mount St. Helens, Washington -
Ash and Tephra, http://vulcan.wr.usgs.gov/Volcanoes/MSH/Tephra/framework.html, Lyn Topinka, 02/08/2005
Unites States Geological Survey, Volcanic Sulfur Aerosols Affect Global Climate and the Earth's Ozone Layer, http://volcanoes.usgs.gov/Hazards/What/
VolGas/SO2Aerosols.html, 02/08/2005
Richard W. Birnie, “INFRARED RADIATION THERMOMETRY>OF CENTRAL AMERICAN VOLCANOES”, http://www.dartmouth.edu/~volcano/BiThesis.html, 03/28/1997, Richard E. Stoiber et al.
Kenneth A. McGee et al., Impacts of Volcanic Gases on Climate, the Environment, and People, http://pubs.usgs.gov/of/of97-262/of97-262.html, U.S. Geological Survey Open-File Report 97-262, May 1997
EPA. "EPA: Global Warming: Climate." http://yosemite.epa.gov/oar/globalwarming.nsf/content/climate.html, U.S. Environmental Protection Agency, 07January 2000.
Goodman, Steven. Earth's Atmospheric Layers and Temperature Variations. http://www.ghcc.msfc.nasa.gov/MSU/atmos_layers.html. Michigan State University Science. 31 July, 1997.
Shah, Anup. "Introduction - Global Issues." http://www.globalissues.org/EnvIssues/GlobalWarming/Intro.asp, 29 January 2006.
Pictures from Corbis.com.
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