209 8 Global Concerns When you first look into climate change, you realize how little you know. The more you look into it, the more you realize how little anyone knows. Dr. Ralph Cicerone, UC Irvine, March 1992 Mercury from China, dust from Africa, smog from Mexico — all of it drifts freely across U.S. borders and contaminates the air millions of Americans breathe … USA Today , March 14, 2005 In ancient times the Earth had periods when maximum CO 2 concentrations were 6,000 ppm (in the Carboniferous period). But life still goes on. There is no proven link between human activity and global warming. Yury Izrael, IPCC vice president, June 2005 The earth and its atmosphere are a dynamic system of which human activities form only a small part. Meteorology and long-range transport of pollutants, geogenic versus biogenic versus anthropogenic emission sources, air pollution control strat- egies, ocean temperatures, volcanoes and sunspots, as well as their second order effects, make for a system too complex to truly understand. In no other area of air quality management is there greater uncertainty than in some aspects of global issues. Other issues — such as intercontinental pollution transport and stratospheric ozone impacts — are clearer because observation and measurement methods have improved with time and there is a longer record of such measurements. However, proven facts are still few and opinions are many regarding human air pollutant impacts on issues such as climate and acid rain. Popular concerns for intercontinental pollution transport deal with chronic health effects and fairness issues; stratospheric ozone concerns are for potential surface UV light penetration and fears of cancer; climate change concerns include the potential for rising sea levels or impacts on agriculture; acid rain issues include possible effects on vegetation and food supplies. In each case we know some things well, such as temperatures and gas concen- trations at various points and times. In other cases, the best we have are various theories and computer models. The concerns are many, and the potential costs are high. This is not unexpected since the impacts of any global air quality management approach will potentially affect virtually every area of society. The implications and fears are many: agriculture, health, economics, business and international relations are at stake. 7099_book.fm Page 209 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 210 Principles of Air Quality Management, Second Edition It is certain that no one has all the answers, but we will investigate what is known in this section. THE CHALLENGE It is appropriate to speak of change in measurable parameters and calculations. However, terms such as loss or fluctuation reveal different levels of knowledge, or, more appropriately, theories and presuppositions. When speaking of change, it can be said that there are mathematical differences in measurable parameters versus time. Thus, differences are measured in physical parameters, so conclusions can be based on the scientific method and evidence. Terms such as loss imply an irrevocable or irretrievable diminishment in some quantity that may not be verifiable. Fluctuation denotes a dynamic process over time, which may be a better term to use when dealing with changing data whose true cause is unknown. The challenge is to evaluate changes accurately without becoming advocates. One goal is to be fully cognizant of the accuracy of our measurements. Parameters that can only be modeled, estimated or assumed are based upon presuppositions. An open-minded appraisal of measurable facts is the best approach. At all times, researchers need to be fully cognizant of the uncertainties and potential discrepancies in such models as new evidence becomes available. The reason that one must be careful of the information that models yield is that they are, at best, approximations based on limited data sets. Therefore, small changes in input data, factors, or other “constants” may produce significant changes in modeled output. Of course, direct measurements, such as satellite photographs of the transcon- tinental transport of air pollution from a source location to a receptor location, are proof of a source/receptor relationship. Pollutant profiling (determining a pollutant’s chemical concentrations and ratios) at such a receptor is another strong proof of the source of the air pollutant. D ATA AND R ECORDS With respect to scientific measurements, there is only a very limited period of time during which accurate real-time measurements of the physical world have been taken. For some parameters (pH), the maximum time period over which we have accurate measurements is about 150 years. In other cases, such as the existence of methane , our quantitative knowledge dates back barely 200 years. Therefore, to evaluate potential air quality management strategies for global impact, one must take into account other evidence available for time periods prior to real-time scientific measurements. This allows for model calculations to be put into perspective. It must be remembered, for instance, that the CO 2 concentrations measured at Mauna Loa, Hawaii, and used as illustrative of the trends of carbon dioxide in the atmosphere, have only been made since 1958. All other CO 2 data purporting to represent long-term concentrations is inferred and subject to interpretation. Also, changes in calibration method alone may introduce dicontinuties in data sets even though an instrument remains the same. 7099_book.fm Page 210 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Global Concerns 211 When concerned with long-term issues in which we do not have consistent mathematical data, written historical records are our initial source of information. For example, historical accounts of climate experienced by various population groups allow us to make general statements relating to climate, such as the “little ice age” that began in 1306 AD and peaked in Europe in the late seventeenth century. Likewise, agricultural patterns may allow us to see the general trend of climate in a location. For example, during the height of the Roman Empire, North Africa was considered the granary of the Empire since wheat was grown throughout that region. This indicates that there once was a much wetter climate in that area than at present time. Recent NASA satellite observations show river channels with com- plete riverine tributary systems buried beneath the sands of the Sahara desert, verifying greater rainfall in the past. Core sediments from the Dead Sea indicate that rainfall was abundant in the Middle East until about the fifth century AD, whereas today only salt is mined; so modern research is a valuable tool. Indirect evidence, such as tree rings or gas compositions of microbubbles in ice cores, may or may not point to climate changes as well. However, it is important to realize that indirect records are open to interpretation. The degree of accuracy of indirect evidence compared to present levels of instrumentation and real-time data is limited at best; however, these records do allow for qualitative trend analyses over periods of centuries. Our focus must therefore be on what is known to be true from: (1) observable facts, (2) historical records, and (3) indirect evidence. From this information, one may develop models, “what if” scenarios, and alternate views of the same data. With these approaches, different societal management options may be developed. In all events, we must be aware of the uncertainties in any theory beyond that which is verifiable by measurement techniques. And we must be careful not to hold onto theories or models so tightly that it blinds us to the truth of measured data. INTERCONTINENTAL POLLUTANT TRANSPORT The movement of air contaminants from one location to another has been fairly well known on a local or statewide level, but it has only been in the last five years — with the advent of air quality instrumentation capable of measurements in the low part per billion levels, high speed telemetry, and satellites — that the phenomenon of intercontinental pollutant transport has come to the attention of the scientific community. Popular articles in the United States indicated that in 1998 a plume of smoke drifted north from fires that had been set by farmers in Central America to clear fields. It blanketed cities from Texas to Pennsylvania. The plume was so thick that it caused partial closure of the main airport in St. Louis, Missouri. That same year dust from the Gobi Desert in China headed for North America. It was reported in USA Today that “you could actually see it like yellow ink snaking across the Pacific.” The particulate matter in the cloud was so dense that when it reached the United States, officials in Washington and Oregon issued warnings of unhealthful air quality. 7099_book.fm Page 211 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 212 Principles of Air Quality Management, Second Edition Evidence of intercontinental pollutant transport can be seen in a NASA satellite photograph of a dust plume traveling from North Africa to the Caribbean, Central and South America (Figure 8.1). Other photographs are available from NASA on the World Wide Web. T HE D ATA Transcontinental movement of air pollution is a serious issue because it threatens the ability of nations to achieve their own air quality objectives. Among those concerns are chronic health impacts and attainment of the national ambient air quality standards. Recent studies have indicated that transcontinental movement of criteria and toxic air contaminants, particularly from developing nations to the United States, is serious and threatens the progress made in attaining our air quality goals. Among the recent reported findings are: • Mercury emitted by power plants and factories in China, Korea, and other parts of Asia travels to the United States and settles into the nation’s lakes and streams. •EPA estimates that 40% of the mercury in the air in the United States comes from overseas. • Aerial- and ground-based sensors have detected the chemical fingerprints of air pollutants floating across the Pacific and Atlantic oceans. •Particulate matter and dust from Africa’s Sahara Desert blows west across the Atlantic Ocean, which raises particulate levels above federal health standards in Miami and other Southern cities. FIGURE 8.1 A NASA satellite photograph of a dust plume traveling from North Africa to the Caribbean, Central and South America. 7099_book.fm Page 212 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Global Concerns 213 • Ozone and visibility reducing aerosols from factories, power plants, and fires in Asia and Mexico impact pristine spots, such as California’s Sequoia National Park and Texas’s Big Bend National Park. • Los Angeles may get as much as 50 parts per billion of the ozone it monitors in the summer from overseas. According to researchers from NOAA, air pollution wafting into the United States accounts for 30% of the nation's overall ozone problem. By the year 2020, “imported air” pollution will be the primary factor degrading visibility in our national parks. U.S. law requires the restoration of natural visibility in places such as Arizona’s Glen Canyon National Recreation Area. But haze caused by Asian dust storms sometimes obscures the landscape in the parks. The haze could make it difficult, if not impossible, to reach federal visibility goals, and it impacts people’s health due to the ultrafine particle size of the haze. C ONCLUSIONS Intergovernmental cooperation in reducing air pollutants at their source is no longer restricted to local authorities; it is now needed between nations and continents. If national long-term air quality goals are to be achieved, it will take the type of cooperation seen when the problem of stratospheric ozone was addressed, as noted in the following section. STRATOSPHERIC OZONE Probably the most significant success story in global air quality management is the issue of stratospheric ozone (the ozone hole) and the improvements seen and mea- sured to date. Human health, and the flora and fauna of a remote location — Antarctica — were threatened by increased ultraviolet (UV) radiation. To deal with the threat, reasoned scientific data was applied to a real world problem and a solution was chosen which worked in an amazingly short time period of less than 20 years. This issue represents the highest fusion of scientific research, data analysis, and applica- tion of a global management decision to ameliorate a threat to the environment. R ADIATION P RIMER The reason for the concern for stratospheric ozone change lay in the fact that certain simple molecules absorb incoming sunlight, which contributes to decreases in sur- face radiation. As seen earlier, there are significant differences between the high altitude intensity of incoming solar radiation and the intensity measured at sea level. While it is true that ozone at the earth’s surface is a deleterious material, at high altitudes it has a beneficial effect by blocking certain wavelengths of harmful solar radiation as we saw in Figure 5.1 earlier. In Figure 8.2, we see a comparison of radiation curves over the entire wavelength of incident sunlight, from 0.1 to 100 microns (on a logarithmic scale) and that generated by two surface temperatures: 5800˚ and 245˚K. The curve on the top left is the incident radiation from the sun’s 7099_book.fm Page 213 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 214 Principles of Air Quality Management, Second Edition surface (at 5800˚K) as a function of wavelength. The curve on the top right is the emission characteristic of the earth’s surface temperature as a function of wavelength. Incident solar radiation appears in the higher energy (shorter) wavelengths, whereas that of the earth and its re-radiation is concentrated in the longer or infrared regions. The overall effect of altitude on radiation absorption is seen in Figure 8.3. All of the gases from ground level to stratospheric levels contribute to light absorption (dark areas). A comparison of the radiation absorption at higher altitudes (11 kilo- meters) to that at the surface indicates the significant absorption due to the depth of the atmosphere and its constituent gases. Figure 8.3 illustrates the relative absorptivities of different gases in the top five bands with a summary in the bottom band. All of the gases in these five bands are energy-absorbent gases and each has its own characteristic absorption wavelength. Water is the greatest greenhouse gas of all because of its strong absorption from 0.8 to over 15 microns, which spans the infrared region. Water, while varying dramatically, exists in the atmosphere in the range of 0.1 to 7%. Of significant concern for stratospheric ozone is the third band in Figure 8.3. It shows the very strong absorption characteristics of oxygen and ozone in the ultra- violet regions between approximately 0.2 and 0.3 microns. Ozone is primarily responsible for this absorption. The absorption characteristics of oxygen, while lower FIGURE 8.2 Radiation emission and absorption curves. 5800°K 245°K Ground level 11 km Black body curves 0.1 1 2 3 5 10 15 20 30 50 1001.50.2 0.3 0.50.15 (a) (b) (c) 0 20 40 60 80 100 0 20 40 60 80 100 Wavelength (microns) Absorption % Intensity (normalized) 7099_book.fm Page 214 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Global Concerns 215 than ozone, is significant due to its roughly 21% concentration in the atmosphere. (It is interesting to note that the 6% greater density and oxygen partial pressure of the atmosphere at the 1,400 foot [below sea] level of the Dead Sea filters out nearly all of the incident UV radiation such that its beach is a health spa for people with skin diseases.) Stratospheric ozone, therefore, serves as a protective layer for the surface of the earth, since it is known that ultraviolet radiation may have harmful effects not only on human health, such as skin cancer, but potentially on the phytoplankton in the earth’s oceans as well. S TRATOSPHERIC O ZONE F ORMATION The ozone in the upper atmosphere was assumed to be in a steady state condition. Equations 8.1 through 8.3 indicate the general chemical reactions occurring in the upper atmosphere. O 2 + h ν → 2O* (8.1) O* + O 2 → O 3 (8.2) O 3 + h ν → O 2 + O* (8.3) These gases are normally in a natural equilibrium, absorbing ultraviolet radiation to form ozone and then reforming oxygen with absorption of additional ultraviolet radiation. The formation and equilibrium concentrations found in various parts of FIGURE 8.3 Molecule-specific absorption curves. 0.1 0.2 0.3 0.4 0.6 0.8 1 1.5 2 3 4 5 6 8 10 20 30 0 100 100 100 100 CH 4 N 2 O O 2 and O 3 CO 2 H 2 O To ta l Wavelength (microns) A b sorption % 7099_book.fm Page 215 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 216 Principles of Air Quality Management, Second Edition the earth’s atmosphere vary according to latitude, wind velocity, sunspot activity, and temperature. E ARLY O BSERVATIONS The above reactions were not of concern until measured observations indicated a disturbance of the ozone–oxygen equilibrium over the Antarctic in the 1980s. It appeared that certain man-made chemicals had a correlation with decreases of the stratospheric ozone column during October (the Southern Hemisphere’s springtime). The theory was that anthropogenic emissions of chlorine containing compounds, including certain gases, chlorofluorocarbons (CFCs), contributed to the perturbation of the stratospheric ozone equilibrium. Lab studies indicated they had a part in scavenging the ozone radicals, which depressed the overall formation rate. The CFCs and related bromine containing compounds were used as refrigerants, solvents, and fire-extinguishing agents, as well as industrial foam blowing agents. T HE R ESPONSE Regulations were implemented which phased out these CFCs in the United States by 1996. Other nations agreed to phase out the use of CFCs by the year 2000. Because the diffusion rate of CFCs into the stratosphere is not instantaneous and there are latitudinal variations in concentration, there was a suggested lag time of 20 to 30 years for the maximum effect of CFCs to the depletion of ozone in the stratosphere. O THER S OURCES AND V ARIATIONS Natural sources of chlorine such as volcanoes were thought to have a significant impact quite apart from the impact of CFCs in terms of ozone-depletion potential. Scientists estimate that volcanoes annually dump 12 million tons of hydrochloric acid into the atmosphere, but only a portion reaches the stratosphere. The 1976 eruption of Mount St. Augustine in Alaska emitted more than 175,000 tons of chlorine compounds into the stratosphere. Some scientists recall that the 1982 eruption of El Chicon in Mexico thinned the ozone column by 20% as the chlorine- containing volcanic cloud mixed with the lower portions of the ozone layer. There were historical disputes as to whether the ozone column changes noted in the last 15 to 20 years were truly a result of anthropogenic emissions. For instance, the amount of ozone depends directly on the flux of ultraviolet light from the sun, which varies with the 11-year solar cycle. There are shorter cyclic periods in solar output, which will also change stratospheric ozone concentrations. Increases in sunspot activity, therefore, could be expected to and do indeed contribute to higher ozone levels in the stratosphere. Satellite data show variations between 0.25 and 0.65% in the stratospheric ozone content every 13.5 days. These variations corre- spond to changes in ultraviolet emission from the sun, thus verifying that there are shorter time periods of solar output variability, which also contribute to ozone variations. 7099_book.fm Page 216 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Global Concerns 217 L AB S TUDIES The reactions that were found to occur in the laboratory and appeared to show correlations with ozone depletion in October in the Antarctic are summarized in Equations 8.4 through 8.6: CF 2 Cl 2 + h ν → Cl* + CF 2 Cl* (8.4) Cl* + O 3 → ClO + O 2 (8.5) ClO + O* → Cl* + O 2 (8.6) These lab studies indicated that CFCs slowly migrate to the upper atmosphere and absorb incident radiation to generate a free radical chlorine atom plus free radical CFC fragments. In the next step, the free radical chlorine attacks ozone molecules to yield chlorine monoxide (ClO) and molecular oxygen. The chlorine monoxide further reacts by scavenging atomic oxygen (free radicals) to yield, once again, the free radical chlorine atom plus oxygen. The overall effect, therefore, is for the chlorine free radical to destroy the ozone as well as oxygen free radicals, which disrupts the normal equilibrium state. This reaction was held to be responsible for diminishment of ozone concentrations in the stratosphere. The reason CFCs were found to be important is that they are virtually nonreactive in the lower atmosphere and slowly diffuse to the stratosphere, where ultimately they are exposed to high altitude ultraviolet radiation. That ultraviolet radiation is sufficient to split the molecule, yielding the free radical chlorine atoms. Laboratory studies indicate that the ozone destruction effectiveness of a chlorine free radical is between 10,000 and 100,000 oxygen free radicals before it is ultimately removed from the process by reactions with hydrogen-containing molecules to yield HCl. A NTARCTIC S TUDIES The effect on stratospheric ozone was originally noticed as a short-term phenomenon in the extreme Southern Hemisphere in early spring rather than a continuous deple- tion process. Some salient facts on the characteristics of the atmosphere over Ant- arctica are helpful in the attempt to understand these phenomena. First, the air over Antarctica is isolated from the rest of the global circulation patterns during the winter. The patterns are the result of the lack of air disturbances in the higher southern latitudes due to fewer continental land masses in that hemi- sphere. This leads to the formation of an isolated polar vortex in which the local atmosphere is cut off from other air currents. Also significant is the 10 to 20˚K colder temperatures over Antarctica than over the Arctic. This condition causes stratospheric ice clouds, which are not seen to the same extent over the northern high latitudes. 7099_book.fm Page 217 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 218 Principles of Air Quality Management, Second Edition The key appears to be the sudden release of reactive chlorine at the end of the Antarctic winter (September/October). Nitrogen dioxide reacts in the gas phase with chlorine monoxide to yield chlorine mononitrate (ClONO 2 ). This compound can convert other chlorine species into chlorine gas, which readily dissociates into chlorine free radicals. Chlorine mononitrate, when condensed, reacts rapidly with heterogeneous materials on the surface of an ice particle but not in the gas phase. Thus, at the very cold air temperatures above Antarctica, virtually nothing happens during the winter months, except to convert chlorine mononitrate into a solid form on an ice particle surface. With the first appearance of sunlight in the Southern Hemisphere springtime, chlorine free radicals are readily formed to enter into reac- tions with ozone, causing a drop in ozone concentrations during those early spring- time weeks. This sequence, coupled with the breakdown of the polar vortex and heating of the atmosphere in the springtime, causes mixing and dilution of the polar vortex gases with ozone-containing atmospheric parcels from the Southern Hemisphere to reestablish the ozone layer over the Antarctic. It has been observed that the tremen- dous gradients in concentration of ClO and chlorine mononitrate appear to shift by as much as 5˚ in latitude from one day to the next. This illustrates the importance of the disturbances of the polar vortex in determining the chemical compositions of the Antarctic air. With respect to the Northern Hemisphere, these effects are not seen due to the warmer temperatures, better atmospheric mixing and lack of available ice particles to create the sudden loss of stratospheric ozone. UV D ATA AND O THER I MPACTS One of the major concerns for potential stratospheric ozone depletion was that UV radiation would increase. During the period when CFC concentrations in the strato- sphere were increasing, the ground level UV radiation was monitored. From these monitored data, it has been found that ultraviolet radiation over the United States decreased. Figure 8.4 shows the measurements of decreasing UV radiation of as much as 7%. In fact, it was found that ultraviolet radiation over the United States decreased during the whole monitoring period. This was a clue that there were more parameters involved than just ozone concentrations. The sites in Figure 8.4 illustrate the natural variation in UV radiation to be found at various locations representative of different latitudes and elevations. Tallahassee (FL) and Oakland (CA) are at sea level, Minneapolis (MN) is at 255 meters above sea level, and El Paso (TX) is at 1194 meters. El Paso and Tallahassee are at about the same latitude (approx. 31˚ north). Oakland is at about 38˚ and Minneapolis is at about 45˚ north latitude. General trends can be seen in this monitored data. From Figure 8.4 it appears that the higher the elevation (El Paso versus Tallahassee), even at about the same latitude, the higher the UV radiation. Also, the higher the latitude (all sites), the lower the incident UV radiation. Location, thus, appears to be the most significant factor in UV radiation dose. 7099_book.fm Page 218 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC [...]... 222 Friday, July 14, 2006 3:13 PM 222 Principles of Air Quality Management, Second Edition TABLE 8. 1 Median Variable Ionic Concentration (mg/L) 197 9 -8 4 of Atmospheric Deposition Program (NADP) sites Ion pH SO42– NO3– NH4+ Ca2+ Lamberton, Minnesota N Atlantic Lab, Massachusetts Kane, Pennsylvania 6.00 1 .88 1.74 0 .81 0.49 4.67 1.54 0.73 0. 08 0.13 4.27 3. 48 2. 08 0. 28 0.16 primarily due to the difficulties... Others Water vapor FIGURE 8. 6 Greenhouse gas contributions © 2007 by Taylor & Francis Group, LLC 7099_book.fm Page 2 28 Friday, July 14, 2006 3:13 PM 2 28 Principles of Air Quality Management, Second Edition 350 Billions of tons/year of CO2 300 250 200 331 150 223 216 100 50 28 0 Oceans Vegetation Soil microbes Anthropogenic FIGURE 8. 7 A recent calculation of nongeogenic sources of CO2 While there is no... 230 Principles of Air Quality Management, Second Edition TABLE 8. 4 Global Methane Emissions Source Tons/Year* % 146.6 142 72 62 60 25 28. 8 28 14 12 12 5 Swamps, lakes, and marshes Rice paddies Animals Anthropogenic Jungles and forests Biomass burning (all) * Millions Source: Dr Don Blake, Ph.D Dissertation, UC Irvine, 1 984 CH4 March–May, 1 983 1.70 ppmv 1.60 1.50 1.40 60 30 N 0 Equator 30 60 S FIGURE 8. 9... evaluate modeling results for a variety of greenhouse gas concerns through the present and © 2007 by Taylor & Francis Group, LLC 7099_book.fm Page 2 38 Friday, July 14, 2006 3:13 PM 2 38 Principles of Air Quality Management, Second Edition balance them with the levels of uncertainties mentioned here Some of MECCA’s model findings to date are: 1 As CO2 increases, the rate of global warming decreases Increases... 3:13 PM 240 Principles of Air Quality Management, Second Edition l pe Bel Relative CO2 assimilation rate 1.4 pp er 1.3 o nw tto o od C 1.2 to ma To 1.1 1.0 0.9 6 10 14 18 22 26 30 34 Leaf temperature (°C) FIGURE 8. 18 Relative CO2 assimilation rate (net photosynthesis) as a function of leaf temperature concentrations of CO2 Fruit tree production is verifiably enhanced When concentrations of CO2 are increased... coldest on record in the history of Europe There have been correlations of solar activity with carbon-14 content of tree rings The rings yield an integrated long-term record of apparent temperature changes corresponding to carbon-14 content (They may also correlate with rainfall.) Comparing carbon-14 records to climate history, one group of researchers found that six of the last seven most severe decreases... Concerns 237 Predicted sea level rise (feet) 30 25 20 15 10 5 0 1979 1 981 1 983 1 985 Year 1 987 1 989 1991 FIGURE 8. 16 Predictions of the rise in seal level resulting from the greenhouse effect plotted against the year in which the prediction was made The predictions decreased from 25 feet in 1 980 to 3 feet in 1 985 to 1 foot in 1 989 Today predicted rises are given in centimeters As noted earlier, the... Helens alone averaged 1 .8 million tons of CO2 per year over the year following the 1 980 eruption Mammoth Mountain, in California, currently emits between 80 0 and 1200 metric tons per day of CO2 or about 0.5 million tons CO2 per year on an ongoing basis.) Even more interesting is the distribution of anthropogenic CO2 emissions by location Figure 8. 8 shows the percentage of total man-made CO2 by global location... 14, 2006 3:13 PM 232 Principles of Air Quality Management, Second Edition 0.4 (a) 0.2 C° 0.0 −0.2 −0.4 −0.6 0.4 (b) 0.2 C° 0.0 −0.2 −0.4 −0.6 187 0 189 0 1910 1930 Year 1950 1970 1990 FIGURE 8. 11 Observations of temperature variation from the mean in the (a) Northern and (b) Southern Hemispheres 130 years in the Northern and Southern Hemispheres, which indicate that the majority of the temperature increase... Temperature (°F) 12.1 11 .8 53.0 11.5 11.2 52.0 10.9 10.6 51.0 50.0 189 5 Temperature (°C) 12.4 54.0 10.3 10.0 1905 1915 1925 1935 1945 Year 1955 1965 1975 1 985 FIGURE 8. 12 Annual average temperature for the contiguous United States from 189 5 to 1990 increases of anthropogenic gas emissions, such as CO2), the United States experienced a slight cooling trend Of course, the year-to-year variability is much . & Francis Group, LLC 2 18 Principles of Air Quality Management, Second Edition The key appears to be the sudden release of reactive chlorine at the end of the Antarctic winter (September/October) 214 Principles of Air Quality Management, Second Edition surface (at 580 0˚K) as a function of wavelength. The curve on the top right is the emission characteristic of the earth’s surface. modeled output. Of course, direct measurements, such as satellite photographs of the transcon- tinental transport of air pollution from a source location to a receptor location, are proof of a source/receptor