IMPORTANT: Read over parts of the chapter 12 on ARID REGIONS, DESERTIFICATION, AND GLACIATION and notes herein. Lacking more detailed notes in your text the web notes here are more complete. In addition you are encouraged to explore some of the excellent links to climate and climate change that you will find later in these notes.

What are the major gases in the atmosphere?

Listed in order of abundance

• N₂,O₂,Ar,H₂O, CO₂

Percentages

• 78.08 % Nitrogen
• 20.95 % Oxygen
• 0.93 % Argon
• < 1% H₂O
• 0.0360 % CO₂ (360 ppm)

What if any changes are there in the atmosphere?

What's the tie between atmospheric pollutants and gases and geology, or what evidence can come from geology that provides insights into atmospheric change?

What's the cause of the changes?

What role have humans played in atmospheric changes?

How do we distinguish human effects from natural variation?

What are the consequences of change?


How do we know what the atmosphere USED TO BE LIKE?

How does one take a sample of the ancient atmosphere?

• Moana Loa measurements
• Carbon 14 pre WWII (wine!!)
• Gas Bubbles in ice in glaciers
• Isotopes of oxygen in CaCO₃ in ocean sediments
• Models based on plate tectonics, weathering, and sedimentation of CaCO₃

More on this later in the lecture.

Atmospheric chemistry change is linked to CLIMATE CHANGE. Prediction of the direction and magnitude of that change is difficult to assess, and more controversial to suggest changing if the predicted effects have not been seen yet. Controversial because:

1. Links to our use of fossil fuels and propellants (CFC's). Demonstrated changes, difficult to assess.
2. Successful prediction of change exceeds our present abilities yet we're still asked to predict change and its consequences. Pits the frontier of science against powerful social, political, and economic interests.

Numerous health threats exist from atmospheric pollution ranging from direct effects of smoking on lungs and cancer to subtle, longer-term effects related to elevated levels of ozone and ultraviolet radiation from use of CFC's (Chlorinated Fluorocarbons) in refrigerants and propellants, to very long term effects related to greenhouse gas increases in the atmosphere. The effects on human health are both direct and indirect. The following lists a few examples of direct and indirect effects of pollutants

1- Direct effects

Ozone

Produced from automobile emmisions. Unburned hydrocarbons from exhaust fumes are photochemically reactive and produce, among several pollutants, ozone. A strong oxidant, and deadly in high concentrations it can accelerate the breakdown of organic substances, and is claimed to shorten life. In low, part per million concentrations, it has a distinctive "sweet" odor, but in higher concentrations the nose is insensitive to its smell. It is not uncommon to smell ozone in the desert region over 100 miles east of the Los Angeles basin, and as you approach Los Angeles you are no longer able to smell the ozone, that is surely there.

Los Angeles has one of the most stringent pollution control authorities, and gas emission device requirements on cars sold in the area are far stricter than most other cities in the world. Despite such efforts smog is a major problem in the basin. Los Angeles is siuated in such a way to provide the maximum effect of auto exhaust emissions on smog production, and the mountains to the east of the city block the air in the basin allowing the buildup of smog to dangerous levels. Smog is a growing problem in numerous other cities in the U.S. where automobiles are abundant, including, Denver, Chicago, Milwaukee, New York, Philadelphia, Atlanta, and Salt Lake City

Sulfur dioxide

Sulfur dioxide is produced in "stack gases" from the smelting and roasting of sulfide ores to produce metals, such as copper, lead, and zinc. The sulfur dioxide is in itself poisonous, but in the atmosphere can oxidize to form sulfuric acid, one of the types of acid precipitation or "acid rain" (See indirect effects below)

Radon gas

A radioactive gas produced in the chain of decay steps of natural uranium and thorium to form stable lead. Radon decays by alpha particle emission, a heavy, and low energy particle that is easily stopped by a thin sheet of paper, or a few feet of air. Once in lungs, however, the radon decay can damage tissue, and lead to long term risks due to cancer.

Common in regions with soils and bedrock high in uranium (granitic rocks) the gas is not hazardous in very low concentrations, but in restricted areas, such as poorly ventilated basements, it can accumulate in high enough concentrations to be considered hazardous to health. Perhaps overblown in its health risks, much of the risk assessment assumed continuous exposure to basement concentrations of radon. Given that few people spend large amounts of time in poorly ventilated basements the risks are somewhat lower than expected, but nonetheless worth concern in areas of high radon risk. Inexpensive home radon testing kits are widely available, but not all are reliable in how they are used to measure concentrations, and the vaues that they record.

2- Indirect effects

CFC's

Chlorinated fluorocarbons are commonly used as refrigerant fluids and as propellants for commercial spray products. Elevated levels of CFCís in the atmosphere ultimately lead to increased levels in the upper atmosphere. Ozone, a beneficial gas in the upper atmosphere is capable of absorbing ultraviolet radiation, thereby reducing levels of UV radiation that reach the earthís surface. CFCís play a catalytic role in changing the rate of ozone production (decreasing it), and the lowered levels have dramatically increased the average level of UV radiation reaching the earthís surface, especially in high altitude environments (e.g. skiiers and hikers beware), and in areas with few clouds (e.g. deserts). Skin cancer is a direct result of long exposure to UV radiation, and there is growing evidence that common sunblock agents are less effective than claimed. A cool tan in the summer and after Spring break looks neat, but when you reach age 50 or older you may pay the price.

SO₂

Sulfur dioxide emissions from smelter stacks oxidized to sulfate producing sulfuric acid, perhaps the most common form of acid rain. The effects of stack emissions used to be local, and major mining areas, such as Sudbury, Ontario (Canada) used to be surrounded by hundreds of square miles of totally barren ground. To alleviate the problem they constructed gigantic stacks, several hundred feet high, but essentially made no changes in the stack effluents. The net effect was to spread the gases regionally, producing low pH rainfall over a much larger region to the east, all of which has more subtle, but just as devastating effects. (Fish spawning, soil fertility, vegetation growth, stream water chemistry, and lakes fertility were all shown to be effected by this acid rain, especially in the upper midwest and northheastern U.S.

Carbon dioxide (CO₂)

One of the most effective of the greenhouse gases, cabon dioxide along with water vapor, methane and some forms of nitrogen (Nitrous oxide) provide the ìthermostatî that makes the earth a habitable planet. The accelerated INCREASE in fossil fuel burning to carry on life in our industrialized world has increased the buildup of CO₂ in the atmosphere, and raised concern that global temperatures will increase. The consequences of such are many. Visiting the web page for the Environmental Information Center will provide a wealth of information on the potential effects of climate change in places such as the Pacific Northwest, California, Texas, and Florida.

Inasmuch as CO₂ increases in the atmosphere are direct results of the burning of the earths "fossil fuels", coal, gas, and oil, and inasmuch as the geologic record provides evidence of past changes in the earthís atmospheric carbon dioxide concentration is the focus of much of the lecture material covered on Atmospheric Pollution. (See discussion and definitions below)

Scale of effects

• Atmospheric have effects ranging from short term and local scale to long term and global in scope.
• Local effects Radon, H₂S, CH₄
• Regional effects Acid rain, auto emissions, ozone in lower atmosphere
• Global effects CO₂, CFC's, atmospheric nuclear testing, ozone in stratosphere
  

IRONY: Nuclear atmospheric testing spread hazardous fallout throughout world, provided tracers to improve our understanding of the processes that move the atmosphere.

Primary concern is with atmospheric gases that provide greenhouse warming of the earth and the variations due to natural and human effects

GREENHOUSE GASES AND CLIMATE CHANGE

[Note several excellent links are available that allow you to explore the greenhouse effect, arguments for global change, and actual climate data on which arguments for change are based. You will learn a lot by visiting these sites. A useful list is provided here for your edification.]

A listing of global warming projects that you can conduct yourself. Allows access to useful data on the earth's temperture and carbon dioxide change in the atmosphere:

The greenhouse visualizer is an exciting way to investigate the effects of global warming by greenhouse gases.

McGill University in Canada has a wealth of links to information, discussions, and research groups conducting global climate change research, and if you're taking french as a language you can even read it in french.

NOAA's National Climatic Data Center provides access to data, information, research on climate change, the El Nino Southern Oscillation (ENSO) and its effect on climate, and climate summaries from around the world. You can even generate graphs and plots of data from the extensive archive of climate data.

Solar radiation and the earth

Need to understand something about solar energy and how it is used and trapped by the earth.

Solar radiation peaks in the ultraviolet (UV) range and passes essentially unmodified through a "transparent" atmosphere where it is absorbed by clouds, water, rocks, and soil.

Best analogy is your car on a warm/hot/sunny day

• Window glass is transparent to short-wave radiation (ultraviolet, UV)
• Short radiation passes through the car window and is absorbed by the metal, cloth, and plastic of the car's interior (the darker the material the more efficiently absorbed)
• The absorbed energy warms the materials, and the warmed materials RE-RADIATE energy of a much longer wavelength (Infrared radiation)
• The car's glass is not transparent to infrared radiation, and the trapped heat caused the car's interior to heat up to levels that can be life threatening.

The earth's greenhouse effect works in essentially the same way, and helps to provide a planet whose surface conditions have been and presently are suitable for the origin and evolution of life.

Electromagnetic waves (including visible light) span orders of magnitude in wavelength and energy. Short wave radiation includes gamma rays, x-rays, and ultraviolet rays, and longer wave radiation ranges through the visible spectrum of light to infrared to radio waves.

Visible light spans a narrow range of the spectrum, from 400 to 700 nannometers (400-700 times 10^-9 meters) with blue (near ultraviolet, UV) at the short end of the spectrum and red (near infrared, IR) at the longer end of the spectrum. Do you know a good mnemonic device for remembering the colors of the spectrum? Click here.

Intense solar radiation peaks in the ultraviolet range of wavelengths. The earth's atmosphere is essentially transparent to this radiation and much of it reaches the land and ocean where it can be absorbed by water, rock and soils. A portion of the radiation if reflected off of high clouds and ice and lost to space. The earth's ability to reflect this incoming radiation is masured by its ALBEDO

The absorbed short wave radiation is converted to heat. All bodies at temperatures above absolute zero (-273° C) radiate energy and the peak wavelength of the radiated energy is determined by the bodies TEMPERATURE. As temperatures increase the wavelength of radiation shift toward the ultraviolet end of the spectrum. For example as you heat up a piece of metal, such as a paper clip, needle, or wire, in a flame it is initially dark but as it heats it begins to glow a dull red, then a cherry red, orange, and ultimately nearly yellow-white, at which point it is on the verge of melting.

Thus the sun's surface,which is very hot (>6,000 degrees Celcius) emits short wavelength radiation, and the earth's surface at temperatures from near zero C to over 30 degrees C emits much longer wavelength radiation, beyond red into the invisible portion of the spectrum called INFRARED (beyond red).

Because the earth's atmosphere is nearly transparent to UV radiation, and about 50% of its energy passes through the atmosphere to be absorbed by the earth's surface. Of the remaining portion 30% is largely lost through reflection off clouds and reflective surfaces of the land (especially snow and the polar ice caps). About 20% is absorbed by water vapor, dust, clouds and OZONE.

About 50% of the incoming solar radiation reaches the earth's lower atmosphere and is absorbed by the land and the oceans. The oceans (e.g. water) have a high heat capacity, and it takes much more absorbed radiation to raise its temperture than rocks and soil (especially dark colored rocks and soils with low albedos). [If you don't believe me, then compare sitting on a black rock versus sitting in nearby water on a hot summer day!] Thus, the temperatures of the land tend to vary much more than the ocean, from very cold,Siberian temperatures, to temperatures in excess of 45 degrees C. (113° Farenheit).

The radiated heat (longwave, infrared radiation) fro the earth is absorbed by greenhouse gases within the atmosphere. These gases include water vapor, carbon dioxide, methane, and nitrous oxide. The absorbed radiation can be reradiated, but most of it is trapped within the atmosphere, thus keeping it much warmer than it would be without the effect of absorption.

A global energy budget illustrates to balance between short and long wave radiation.

Contrary to some opinions the earth's atmospheric carbon dioxide concentration has NOT been constant through time, and in fact appears to have changed dramatically over long periods of the earthís history. To understand the potential effects of fossil fuel burning on global climate change in the FUTURE, we need to better understand the processes that controled the climate in the earthís long history. The evidence for changes in the earthís climate is harder to obtain as we go back in geologic time, and the ìsamplesî of the earthís past climate are different for each slice of time in the past.

THE SCALES OF CARBON DIOXIDE CHANGE

The time scales of CO₂ change vary widely from short-term (daily) to "earth age" in scale. One might think of carbon dioxide changes as a nested series of time scales, each of which has its own controls or processes.

DAILY

Photosynthesis is the major control on daily variation. Plants take up CO2 during the day when solar radiation is used to convert carbon dioxide and water into plant hydrocarbons and oxygen gas. The chemical reaction is:

CO₂ + H₂O = CH₂O + O₂

Daily decreases in CO₂during plant growth (peaks early afternoon) are followed by night time increases in CO₂as plant respiration occurs.

SEASONALLY

Most of the land's surface is in the northern hemisphere. Terrestrial plants in the mid to northern latitudes have seasonal losses of leaves as photosynthesis "shuts down" in the winter months. Once taken out of the loop then plant and soil organic matter degradation (respiration) dominates and the CO₂levels in the northern hemisphere increase. In the spring and summer, as plants regain leaves and start photosynthesis the atmospheric CO₂levels decrease in the northern hemisphere.

In the southern hemisphere the effect is just the opposite, but diminished in magnitude due to the fact that there is much land mass in the souther hemisphere.

RECENT HISTORIC SCALE

Records of atmospheric CO₂ have been made over the past 100 years or so, but systematic observations didn't begin until 1958 when a site was set up on Moana Loa in Hawaii. This valuable record is the cornerstone of our evidence for increased atmospheric CO₂ since that time.

CENTURY TO MILLENIAL SCALE

Somewhat more sparse and lower quality measurements of global CO₂have been collected for over 100 years and provide evidence of atmospheric CO₂ levels back to the time of the industrial revolution.

THOUSAND TO 100 THOUSAND YEAR SCALE

Gas trapped within the ice in Antarctica and the Greenland ice sheet provied high resolution measures of co2 levels over the past several hundred thousand years, and demonstrate the range of CO₂variation related to the processes that regulate the circulation of the ocean, and the waxing and waning of major glaciation on the earth.

A second piece of evidence comes from the remains of organisms that live and grow in the ocean. Small zooplankton made up of FORAMINIFERA, an animal that secretes calcium carbonate in its body parts, eventually die and fall to the sea floor where they form thick sedimentary layers that can be dated with a variety of radioisotopic techniques. The oxygen isotopic composition of these fossil "forams" can be used to infer something about the temperature of the ocean's surface water.

MILLION TO 100 MILLION YEAR SCALE

Lacking samples of the earth's atmosphere, and interpretable isotopic information from the sedimentary record, current estimates of past global CO₂ levels are obtained from mathematical models using plate tectonics as the key mechanism for changing the atmospheric gases. Essentially the models involve gases from volcanism (rich in CO₂) and the rates of volcanism determined by the rates of plate motions on the earth over time. Far too complicated to summarize here, one should just know that these models have reached a fairly high level of sophistication. Estimates are that past climates had as much as 20 times present atmospheric levels (PAL).

BILLION YEAR SCALE

Based on evidence that the sun's solar constant (radiative energy released) is INCREASING with time, we would argue that the early sun was significantly cooler at the time the earth first formed. Ancient (4 billion year old) rocks demonstrate that the planet had liquid water on it, as well as periods of glaciation. This implies a climate having temperatures roughly comparable to today's. In order to sustain such temperatures in the past we argue that the CO₂ content of the atmosphere had to be SIGNIFICANTLY HIGHER THAN TODAY'S to provide enough greenhouse warming to keep water in the liquid state.

Where does it come from?

Recent (past 100 years) increases in atmospheric CO2 are directly linked to human causes. Burning of fossil fuels (coal, natural gas, and oil), production of cement, and deforestation have all been implicated as sources of this excess CO₂. The RATE OF INCREASE of atmospheric CO₂is unprecedented historically, and concerns for its effects are many (see web site for the Environmental Information Center)

Where does it go?.

Carbon dioxide is not accumulating in the atmosphere at the rate it is being produced by human activities. Most of the "deficiency" is accounted for by uptake in the oceans, yet some suggest that a part of the "missing carbon" is being taken up by increased growth of plant matter on the continents, a sort of renewed growth stimulated by higher levels of atmospheric CO₂. There is some experimental evidence to suggest that some plants respond to higher CO₂ concentrations by increasing their growth rate.

Counter to this is the suggestion that accelerated DEFORESTATION of the planet through lumbering and slash and burn agricultural production in tropic zones is REDUCING the amount of plant uptake of CO₂. The numbers are extreemely difficult to determine precisely, and you will see various different arguments for either case (increased growth vs deforestation loss). The differences derive from the undertainties in the estimates of what is called the GLOBAL CARBON BUDGET. Be a skeptic.

What are the effects of elevated carbon dioxide levels in the atmosphere?

A doubling of atmospheric CO₂ is postulated within the next 100 years which is predicted to cause a global increase in temperature of a few degrees Celcius (2-4°). Consequences of this are many.

1. Shifting climatic zones of the earth (Some have even suggested that the best place to live ithe world would be Clevaland, Ohio!)
2. Changing temperature regime of lakes forcing changes in fish habitat, reproduction, predation, and survival.
3. An increase in the sea level flooding developed lowlands (1-1.5 feet).
4. An increase in the frequency and intensity of hurricanes and typhoons due to warmer seawater.
5. Icreased forest fire frequency in areas of the west.
6. Increased summer growing season, decreased summer growing season, less snowfall, less skiing.
7. Almost any environmental aspect that would effect the range and survival of plants and animals.

Are ALL these cause for concern?

Some are overblown. The changes that you will see in your lifetime are going to be relatively small, and perhaps the storm and flood frequency effects present the greatest risk. Population pressure on existing resources may cause other environmental changes that have greater short term consequences. It's complicated and the best of minds are yet to agree on the magnitude and effect of all the proposed changes.

What can I do about it? REDUCE THE DEMAND FOR FOSSIL FUELS.

1. Push for greater efficiency of energy use to lower the fossil fuel demands.
2. Reduce energy consumption in ways that YOU can control.
• Keep furnace low in winter, and wear warmer clothing
• Use zone heating for living areas instead of general heating of the whole apartment or house.
• Convert to more efficient fuel burning furnaces
• Learn to sweat in the summer and minimize air conditioning needs. Use fans and open windows to ventilate hot, humid living spaces.
• Wear fewer clothes??
• Cut down on repackaged food items. All require energy to package. Would a glass of ice tea serve as well as a can of colored, flavored, carbonated water in an aluminum can? Reprocessing of aluminum is a VERY expensive energy consumer.
3. Reevaluate the alternate energy sources, especially nuclear energy.
4. Be VERY concerned about population growth. Even with the PRESENT POPULATION we are stressing energy resources beyond limits, and causing sifnificant atmospheric changes. An increased population is certainly not going to make matters better.
5. Return to living in caves, using animal hides for clothing, and eating cold foods. (Deforestation in some underdeveloped countries is driven for the need for firewood for cooking and heating.)

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