NATS 101: Class Notes

1. Wed. Jan. 15
2. Fri.    Jan. 17
3. Wed. Jan. 22
4. Fri.    Jan. 24
5. Mon. Jan. 27
6. Wed. Jan. 29
7. Fri.    Jan. 31
8. Mon. Feb. 03
9. Wed. Feb. 05
10. Fri.    Feb. 07

11. Mon. Feb. 10
12. Wed. Feb. 12
13. Fri.    Feb. 14
14. Mon. Feb. 17
15. Wed. Feb. 19
16. Fri.    Feb. 21
17. Mon. Feb. 24
18. Wed. Feb. 26
19. Fri.    Feb. 28
20. Mon. Mar. 3

Wed. Jan. 15, 2003

   Turn off your cell phone!

Syllabus handed out and key points reviewed; course web site (under construction at www.ltrr.arizona.edu/nats101) explored; Daily readings from Mackenzie textbook are listed in syllabus, but additional readings will be announced and made available through course web site; 2 questions on first quiz will come from list of questions at end of syllabus.

Class roll was obtained by passing around lists where students indicated their presence

Mention of some of the class content (examples of great concern with cooling temperatures in the 1970s; the graph of changing atmospheric CO₂ concentration since 1958 that some have called the most important graph of the 20^th Century; the graph of changing CO₂ concentration over the last 12000 years)

Global Change IQ quiz given in last 10 minutes to get some idea of prior global change knowledge of students coming in to class. (no grades will be assigned)

Note:  15 student volunteers are needed to be group activity group leaders (eligible for 5 points extra credit)- send e-mail with your interest to sleavitt@ltrr.arizona.edu

Note:  Everyone should send Li Cheng (lcheng@ltrr.arizona.edu) a message indicating what e-mail account you would like us to use for the course listserve forum (deadline 5pm Jan. 29) This is a course requirement.

Hand-out (atom size [diameter, mass], moles, speed of light, conversions, etc)

Intro to grand story of epic proportions (sort of like Star Wars, Bible, etc) known as The
          Periodic Table, that establishes a context of time and space in which our world exists

Cast of characters
           Elements arranged according to increasing Atomic Number (number of protons).
           (This arrangement is also related to filling of electrons in discrete electron “shells”)
           Each element has name and 1- or 2-letter shorthand notation.
           When an atom is “neutral”, it will have an equal number of protons (+) in nucleus and
           electrons (-) orbiting nucleus.  Neutrons (no charge) also can reside in nucleus at the
           center of atoms.

Characteristics of matter
           All matter is made of small particles (atoms and their consituents)
           Atoms of the same element have similar chemical properties
           Atoms are not divided by chemical reactions
           Chemical reactions involve electrons; nuclear reactions involve protons/neutrons
           (in a column of period table different elements may behave similarly in chemical rxns)

Isotopes of a given element have same number of protons, but different numbers of neutrons
Scientific notation (examples)
Conversion of units (examples)
Moles (number of atoms in the atomic weight [in g] of an element= 6.02x10²³ atoms for any element)
          

Handout of Laws of Thermodynamics and Newton’s Laws

Terrestrial and continental productivity animation over 3 years from satellite composites in “Colors of Life” web link (http://www.gsfc.nasa.gov/gsfc/earth/environ/carbon/carbon.htm)

Student Conservations Association information (www.theSCA.org) internship opportunities

Finish questions on worksheet handed out last time (conversions, scientific notation)

Back to epic story in Periodic Table of Elements:

Only 2 elements, H & He, were formed in “Big Bang” 15 billion years ago when all matter in universe was contained at a point (“singularity”).  Only H and He formed because universe was rapidly expanding (cooling) and there were progressively fewer interactions between atoms, neither of which was favorable to formation of heavier elements.  Thus, the carbon (C) atoms in your hair and Gold (Au) and silver (Ag) atoms in your teeth did NOT form during the Big Bang.

Elements from lithium (Li) to iron (Fe) produced in the interior of normal stars by “fusion” processes, i.e., lighter elements being combined to manufacture heavier elements.  For example, in our Sun, fusion takes place converting 4 hydrogen atoms to one helium atom; the mass of the helium atom is less than the 4 hydrogens, so the difference in mass is what was converted to energy that contributes to the internal heat of the Sun (E=mc²).  The energy from such nuclear reactions (involving nuclei of atoms) >> energy from chemical reactions (involving electrons of atoms).

Periodic Table (cont’d)

Observations of the Cosmos that fit Big Bang formation of 2 elements in Periodic Table:

1. High cosmic abundance of H and He; abundance generally declines with increasing atomic number but there is also a peak at Fe (iron)

2. Galaxies moving away from us at high speeds; the more distant the faster they are moving away (Hubble telescope deep-space images; Doppler effect and shift to lower frequency and longer wavelength electromagnetic radiation as source moves away from observer; distinct absorption lines of light wavelengths by sodium atoms lead to observation of "red shift")

            Eye-popping, jaw-dropping, awesome demonstration of the Big Bang, in full special

                        effects mode with Dolby® Surround-sound®, and 3-D glasses

The fusion taking place in the Sun and other stars represents a tremendous energy source, and research has been directed at trying to promote controlled fusion reactions on Earth as a limitless source of energy (The world already has many fission reactors in which large radioactive elements such as uranium, decay and release energy)

Elements up to Iron can be produced by fusion because energy is released; Elements beyond (heavier than) iron cannot be produced by fusion, but can be produced by high fluxes of neutrons, such as occur when stars explode (supernova).  Our sun has all of the elements of the Periodic Table, therefore it must have formed from remnants of other stars that have gone through their full life-time of fusion reactions and explosive instabilities

Laws of Thermodynamics

First Law- Energy cannot be created or destroyed, but it can be converted from one form to another (examples of energy- heat, like, kinetic energy, electrical energy, potential energy of petroleum, food and gravity)

Second Law- No energy transformation is 100% efficient or Energy can be converted from one form to another but in all conversions there is formation of some ‘low quality’, ‘non-usable’ heat or Heat cannot be completely converted to work or Universe runs down as energy is dispersed to low-quality heat energy or All systems tend to become random (or dispersed) on their own.  Entropy is a measure of randomness, or dispersion or disorder

The quiz Wed will be given in the first 20 minutes (maybe 25 minutes) of class, with lecture to follow in remainder of period.  There is sample quiz on web page.
Preparation instructions for Group Activity 1 (on Friday) are also given on web page; the groups are also listed on web page.
People who have not yet sent Li an e-mail indicating the e-mail address they would like subscribed to the forum have until 5pm Wed to do so.

            Origin of Solar System
                        There was about 10 billion years between the Big Bang and the origin of our
                                    Solar (Sun) system
                        Our solar system is made of all the elements of the Periodic Table but only He is
                                    being produced in our solar system currently (in the Sun); therefore all of
                                    the elements had to have been produced in the 10 billion years before the
                                    solar system was formed. (our system is from the remnants of other stars)
                        Solar Nebula Hypothesis has solar system forming from a rotating ball of dust and
                                   gases that flattened to a disk shape.  Most of the mass was in the center
                                   and the pressure and temperature in that environment ignited hydrogen
                                   “burning” (fusion).
                        Matter was distributed in the solar system such that the internal 4 planet are more
                                   dense and rocky “terrestrial” planets and the outer “Jovian” planets are
                                   lower density, “icy” planets composed of lighter elements/frozen gases.  
                                   Over 100 other planets have been observed around other distant stars, but
                                   most are quite different than ours (hotter and much, much larger!)
            Newton’s Laws
                        1^st- Every object persists in a state of rest or in uniform motion in a straight line
                                  unless acted on by an external force to change that state.
                        2^nd- The change in velocity (= acceleration) with which an object moves is
                                  directly proportional to force applied and inversely proportional to the
                                  mass of the object (a=F/m)
                       3^rd- Every force or action has an equal and opposite reaction (conservation of  
                                  momentum)
                        Law of Universal Gravitation- any and all objects exert an force of attraction
                                  between them proportional to the product of their masses and inversely to
                                  the distance between them squared. (F= G x (m₁ x m₂)/r²)

Wed. Jan. 29

Quiz 1 from about 12:02 to 12:20 after class took randomly assigned seats.
Deadline for students to send message to Li about listserve is today at 5pm.
            Reminder of Instructions for Preparation for first group activity on Friday appeared on screen from class web page- Each student must bring at least 2             photocopies/printed pages of material (from web/library) to class Friday about the element their group is exploring (particularly information relevant to the             questions listed on the web page). 

Law of Universal Gravitation- example of gravitational force exerted by nearest star (other than Sun) on you at birth vs. the gravitational force exerted by the doctor who delivered you.

Structure of the Earth
          During early stages of Earth history, our planet was at least partly molten resulting from heat of collisions and gravitational potential energy converted to
          heat energy (decay of radioactive elements was also important source of heat over all of Earth’s history)
          During this early period, Earth began to “differentiate” into layers with heavier material “sinking” to interior and lighter material “rising” to surface.
          Consequently Earth’s core is made predominantly of iron and nickel (like some meteorites).  The mantle layer above the core is primarily magnesium
          (Mg) and iron (Fe) silicate (Si and O) rock, and the crust on the surface is composed of silicate rock with less Fe and Mg and more K, Na and Al.
          Even though no one has ever drilled or dug to the mantle, we have samples of the mantle courtesy of plate tectonics.  The sample passed out in class was
          from the upper mantle, brought to the surface in Norway a billion years ago; the rock is called eclogite.

          Presentation about the Student Conservation Association intern program by Dan Pascucci, which finished with a rousing song designed to help us remember www.theSCA.org
Class broke out into the 15 groups and completed Group Activity 1

Revisit group activity #1 with slides of mining activities around U.S. and some of the environmental problems associated with mining

Quiz 1 handed back and answers given and discussed (+1 grade adjustment added to raw score)

Make-up opportunities for GA #1- Students asked to provide availability for BOTH 1-2 Wed and 9-10 Friday for POSSIBLE make-up. Send your availability by e-mail to sleavitt@ltrr.arizona.edu

Structure of the Earth

            Differences in chemistry among layers (for example low SiO2 in mantle and higher in
                      continental crust, and more Fe in mantle and less in crust) is consistent with
                      Earth’s “differentiation” into the layers early in its history.  Contintental crust is
                      referred to as having a granitic composition; oceanic crust a basaltic composition. 
                     The ocean crust is also called “mafic” (dominated by Mg and Fe), whereas the
                     mantle is ultramafic in composition.
           Crust and rigid upper mantle constitute the “lithosphere”.  The lithosphere rides over the
                     portion of the upper mantle (asthenosphere) that flows (heat from Earth’s interior
                     leads to convection processes in the asthenosphere).  The plates move (cm per year)
                     and interact with each other in a dynamic system known as “plate tectonics”. There
                     are 3 different types of plate boundaries.
Plate tectonics and types of plate boundaries (plates colliding = “convergent” boundary;
           platesmoving apart = “divergent” boundary; plates sliding past each other = “transform” boundary. 
           In many cases, besides earthquakes and volcanoes, the location of ore deposits of specific metals
           is related to plate tectonic and plate boundaries.  The richness of metal resources of a country are
          dictated by their current and past position with respect to plate tectonics and other ore-forming processes.

Reminder of GA1 make-ups today 1-2pm and Friday 9-10am (room 104 W. Stadium)
Revisit group activity #1 with slides of mining activities around U.S. and some of the environmental problems associated with mining

Major natural global change events in the first 4.50 billion years of Earth history-
         Earth origin; early heating of Earth and "differentiation" into layers; origin and
         abundance of life; cyanobacteria and changing atmospheric oxygen concentrations;
         banded iron formations (BIF) representing precipitation in early oceans of Fe²⁺ with
         oxygen liberated by photosynthesis, thus preventing an early build up of oxygen; "ice house"
         and "hot house" periods"; early Sun “paradox” when solar luminosity was 30% less than
         present and why the oceans did not freeze (answer= "greenhouse gases" such as CO₂ may
         have been at very high concentrations in early Earth atmosphere)
Today’s atmosphere dominated by nitrogen (78%), oxygen (21%), argon (1%) and “trace gases”
        Origin of atmosphere- "outgassing" of  Earth's interior=> H₂O condenses to form oceans,
        CO₂ and SO₂ dissolve in water; H₂ escapes to space, N₂ and Ar build up, photosynthesis
        builds up O₂ (after BIF oxygen “sink” was filled)
Demonstration of 4 atmospheric gases, some in unusual (cold) forms

Demonstration of the relationship of temperature, pressure and volume for gases, known as the
       “universal gas law” => the product of volume ´ temperature is proportional to temperature,
        ie, if temperature is decreased, you will reduce pressure and/or volume, and conversely if
        temperature is increased, you will increase pressure and/or volume.
In-class writing exercise to describe experiment and explain the cause(s) of the observations.
Today’s atmosphere dominated by nitrogen (78%), oxygen (21%), argon (1%) and “trace gases”.
        If volcanic gases being emitted today are an indication of the gases of volcanoes 4 billion years ago,
        they give us a hint about the evolution of the atmosphere after initial
        "outgassing" of  Earth's interior=> H₂O condenses to form oceans, CO₂ and SO₂ dissolve
        in water eventually forming limestone and Ca-sulfate deposite; H₂ escapes to space, N₂ and Ar build up;
        photosynthesis builds up O₂ (after BIF oxygen “sink” was filled), although “photodisassociation”
        of water vapor molecules in upper atmosphere also produces H₂ and O₂.
Major gases (N₂, O₂, Ar) tend to have constant concentration no matter where and when they are measured
        (for example, N₂ concentrations are very constant everywhere in the world throughout the year),
        but trace gases tend to be more variable depending on where and when measured (for example, H₂O
        concentrations at a location may vary seasonally (ie, summer and winter) and there can be difference
        in concentration depending on where you are in the world, eg, rainforest versus desert)
Sources (mechanism for gas getting into atmosphere), sinks (mechanism for removing gas from atmosphere) and
        importance of some major and trace gases; for example, (a) photosynthesis is a mechanism (source)
        that produces oxygen (CO₂ + H₂O  => CH₂O + O₂ in the presence of chlorophyll and with energy from sunlight),
       (b) we need oxygen to live (importance), and (c) combustion processes can remove oxygen from
        the atmosphere (sink).  An additional source of this information can be found in “Trace Gases” module at 
        http://www.hwr.arizona.edu/Alpine/IGCL/home.html, and in table shown in class.

A handout involving energy and electromagnetic radiation.
Examination of a few of the trace gases (in table from Feb. 7 classnotes), for example water vapor,
              carbon dioxide, nitrogen oxide, sulfur dioxide and ozone that are central to many of
              the global change problems on which we will focus in class.
We live in the bottom of a "sea" of air, with greatest atmospheric pressure at the Earth's surface (at sea level)
Relationship of Fahrenheit, Celsius and Kelvin temperature scales
Temperature structure of atmosphere-- averaged over the whole planet and over the whole year,
               we see temperature change as we go upward into the atmosphere as follows:
               Average surface temperature is +15C (Earth’s surface would be -18C if no greenhouse gases were present).
               As you go further upward, temperature decreases to about -57C at a height of 10 km, which is the top of
                       the lowest atmospheric layer (known as the “troposphere” in which we live, contains nearly all weather
                       on Earth, and has abundant vertical and horizontal air motion)
              The thin layer above the troposphere is called the tropopause where temperature remains constant as you
                       continue to go upward
              As you continue further upward, temperature then starts to warm in the next layer (“stratosphere”, contains
                       the ozone later where absorption of solar ultraviolet radiation contributes to the increasing temperature,
                       and air motion is dominantly horizontal) until it is a balmy 0C at the top of the stratosphere at 50 km.
             Above the stratosphere, temperature is constant in a thin layer known as the “stratopause” and then
                       begins to decrease in the “mesosphere”
What is the causes of Earth seasons?
Electromagnetic radiation is means by which energy is gained and lost by the Earth.
Electromagnetic spectrum in handout with each category of radiation defined by wavelength (l).
“Rules of Electromagnetic (EM) Radiation”- (1) The hotter the object, the shorter the wavelength
             of peak radiation (Wien’s Law determines the peak wavelength, and the temperature of
             any object will determine the wavelength), (2) Shorter wavelengths have greater energy,
             (3) Energy emitted as EM radiation increases as the 4^th power of an objects temperature
             (An object twice the temperature of another emits 16 times as much energy), (4) Objects
             emit visible light (reddish glow) as objects reach a temperature of about 550-600C.

Reminder to bring in 2-3 pages about your country’s water resources to Friday’s GA2.
Graded writing exercise was handed back; Quiz 2 next Wednesday- a sample quiz 2 will appear on website on
           or before Monday morning
Reminder of EC opportunities at Tucson Gem and Mineral Show this weekend, and Gold exhibit at Flandrau Planetarium
Cause of seasons= tilt of the Earth’s axis: when our hemisphere is tilted toward the Sun we have summer,
            and when it is tilted away from the sun we have winter (seasons are opposite for S. Hemisphere,
            but is summer occurs when it is tilted toward sun).
More “Rules of Electromagnetic (EM) Radiation”- Wien’s Law- we calculated peak wavelengths of terrestrial [in the infrared]
           and solar [in the visible] radiation), and an object twice the temperature of another emits 16 times as much energy.
Atmosphere absorbs some wavelengths of terrestrial and solar radiation (Fig. 3.2).  Incoming solar radiation has much
           of its UV radiation removed by oxygen and ozone; outgoing terrestrial radiation is absorbed by greenhouse (GH) gases
           such as water vapor and CO₂.
Our detailed definition of the greenhouse effect- the atmosphere is “transparent” to (ie, it does not absorb) much of the incoming
           solar radiation (like the greenhouse windows), but greenhouse gases effectively absorb many wavelengths of the outgoing
           terrestrial radiation and prevent the energy from escaping to space (like greenhouse windows keeping heat energy in
           the greenhouse).  Suggested that the greenhouse effect is a good thing, without which the Earth’s average temperature
           would be 33C colder; it is the “enhanced greenhouse effect” that is the major global change problem we are currently facing.
Fig. 3 was introduced in terms of the fate of incoming solar radiation (most of which [70%] is absorbed by Earth and atmosphere,
           and 30% of which is reflected by the atmosphere and Earth immediately back to space.  The fate of the 70% absorbed
           will be discussed next lecture.

Sample quiz 2 is now on course web page (answers will be sent to listserve and posted on web
        site Tuesday afternoon); Quiz 2 is at beginning of class Wednesday.
Fig. 3.3- the fate of the 70% absorbed; 45% is absorbed by the Earth’s surface yet the Earth’s
       surface does not get warmer and warmer.  This is because much of the energy absorbed at
       the Earth’s surface gets transferred to the atmosphere by latent heat (evaporation) and
       sensible heat (conduction of heat you feel).  Greenhouse gases (GH gases) absorb and re-radiate
       electromagnetic radiation, maintaining the warmth of the Earth-atmosphere system.  Fig. 3.3 also
       gives us the blueprint for how to change the temperature of our planet or why it might have
       changed in the past.  For example, changing solar luminosity affects incoming solar radiation,
       changing atmospheric or surface albedo affects incoming solar radiation absorbed in
       Earth-atmosphere system, changing abundance of GH gases affects amount of outgoing terrestrial
       radiation prevented from escaping to space
Intro to general circulation- a consequence of greater heating from sunlight at the Equator than at the poles.
      Global air circulation follows convective patterns where air rises at 0° and 60° latitude, and sinks at 30°
       and 90° latitude.  The return flow of wind along the Earth’s surface to replace the rising air results
       in easterly winds (east to west) from 0-30° latitude, westerlies from 30-60° latitude and easterlies
       from 60-90° latitude.
Intro to water cycle- reservoirs where water resides, represented by the amount [mass, volume] present),
      and fluxes represented by movement of water between reservoirs [mass per time, volume per time]) 
       Most water in oceans, most fresh water locked up in ice caps, more fresh water in groundwater than
       surface water.   Fluxes between water reservoirs, eg, runoff the primary direct flux between continents
       and ocean, or precipitation transferring water from atmosphere to land or ocean.

Writing Exercise introduced (handout); Topics were assigned to each student (this info is on
         course web page under “Writing” link, and sample quiz 3 will be posted as well);
         noon Tuesday (tomorrow) is deadline for feedback from students who wish to make up GA3
Comparison of beef-eating habits of all of groups from GA3
Younger Dryas was an abrupt return to cold conditions about 12,000 years ago, after the last ice
         age appeared to end; evidence is seen in Calcium concentration of ice cores; it was likely
         caused by a shift in meltwater discharge from the Gulf of Mexico to the N. Atlantic as
         melting N. American glaciers retreated; increased high latitude precipitation in the future
        enhanced greenhouse world could also contribute to or counteract possible future global change.
Tides- primarily caused by gravity force between Earth and moon (and Earth and Sun); two high tides
        in ocean per day because of tidal bulge facing moon (direct gravitational attraction force- “centripetal”)
       and one on opposite to moon (indirect gravitational force causing "centrifugal force") at the same time.
High biological productivity in upwelling areas and in “estuaries” where fresh water streams encounter
       coastlines in embayments with highly variable environments of salinity (higher salinity toward bottom
       and lower salinity at top) and organism associated with tidal mixing and rates of stream flow.
       Extremely important to commercial fishing.
"Ecosphere"/Biosphere general importance (eg, connected to other parts of Earth system, namely biosphere,
       atmosphere & lithosphere; involved in biogeochemical cycles of elements such as C,O, N, & S; and its
       involvement in energy and mass tranfer)

Handed back quiz 3 and went over answers; also handed back GA3 and other unclaimed graded work; handout of global carbon cycle

Study recommendation- sample quizzes, real quizzes, your lecture notes, my lecture synopses on course web page, readings, group activities; it will be through today’s lecture.

There will be review session Tuesday, 4:15-5:30 in room 312 Space Sciences next to our classroom; It will be driven by the questions of those who come.

Primary productivity is amount of plant matter produced [by photosynthesis] (per area per time)

            Gross Primary Productivity (GPP) is total production

            Net Primary Production (NPP) = GPP-respiration losses

Biomass in oceans is about 0.5% of biomass on continents, but NPP in oceans is almost 1/2 of NPP on continents.  Biomass is needed on continents to provide support to reach light, and therefore the continental biomass is dominated by structural components (CHO).  Marine biomass does not need the structural             components, tends to have a higher ratio of proteins to carbohydrates, and have much shorter life spans than terrestrial organisms

Modern systems have great abundance of species (especially insects), but extinction rates seem to be high.  There have been massive extinctions in the past, unrelated to human activity:

Permian-Triassic extinction event the largest of the 6 major extinction in the Phanerozoic (last 600 million years); evidence from geological record suggesting the possibility it was driven by large volcanic eruptions (Siberian traps) or meteorite/comet impact.  Evidence suggests loss of land plants and lots of sediments, and many "Bucky Balls" (fullerenes) containing inert gases whose isotopic composition suggests extraterrestrial origin.

"Box Models" of biogeochemical cycles require defining the system and subsystems including the reservoirs (compartments, pools) and predicting and evaluating paths and fluxes between reservoirs. 

Carbon cycle cartoon diagram and box model, showing different reservoirs and primary forms of carbon [atmosphere= CO₂, CO, CH₄; hydrosphere= HCO₃-, CO₃-, dissolved CO₂; biosphere= CH₂O; lithosphere= limestone (CaCO₃) and kerogen (oil, coal, and finely dispersed organic matter)]

Terminology: reservoirs/compartments=places where element/compound resides; flux/flow/transfer=rate of movement between reservoirs

Mean residence time (MRT)= reservoir size/flux in (or out)

Turnover rate= flux in (or out)/reservoir size

Sample calculation of MRT of carbon in atmospheric reservoir of global carbon cycle

The next in-class writing exercise will be sometime in the next 3 weeks, and will not be
          announced in advance (however, weight of writing project is much greater than each in-class exercises).
Past CO₂ from carbon cycle models
          Last 600 million years=> evidence that most of the period had CO₂ concentrations from
          about 4 to as many as 18 times the current CO₂ concentration.
Imbalance of carbon cycle related to energy production (for transportation, heating, agriculture and
          other needs of modern society) and consequent transfer of carbon from the lithosphere to the atmosphere
Exponential rise in carbon releases (coal, oil, natural gas, cement, flaring); coal was dominant until about 1970,
          but oil is as great or greater now, and natural gas usage is growing rapidly; global per capita fossil-fuel use
          is about 1 ton per person per year and has been fairly steady over the last 30 years, which means rate
          of fossil-fuel use has been increasing at the same rate as population.
Consequently, fossil-fuel CO₂ release has exponentially increased from less than 0.1 gigatons 150-200 years
          ago to over 6 gigatons per year of carbon today (1 gigaton[GT]= 1 billion tons = 10¹⁵ g carbon);
          political events (Great Depression, WWII, 1970s oil embargo) had a visible but minor effect on this trend.
Reserves of coal, oil and natural gas are enough to sustain us well into future, but their distribution is variable,
          for example US has large reserves of coal and natural gas, but not oil.
Direct CO₂ measurements, beginning with Keeling’s measurement site established in Mauna Loa, Hawaii,
          and providing continuous measurements since 1958; now a world-wide network. Current CO₂ concentration
          is around 370 ppm- about 33% increase since 1958.
CO₂ inputs to atmosphere from oil well fires in Iraq compared to world CO₂ input (6+ Gt/year).

Collected 1^st stage of writing assignment, which will hopefully be returned on Monday.
Prof. Leavitt will not have office hours on Friday (but will be here for class).
Unfinished C-cycle business
        Increase in atmospheric CO₂ concentration has not occurred as a smooth line, but like
               the teeth of a saw blade, with a maximum and minimum concentration each year. 
               This annual “amplitude” (maximum CO₂ to minimum CO₂) change is greatest at high
               latitudes in N. Hemisphere (“seasonal biosphere”). Why is the amplitude low at
               the Equator and in most of the S. Hemisphere?
Nitrogen cycles- lots of air N₂, but plants rely on microbes or nodules (legumes) to provide N in usable
       form (NO₃); Imbalance in N cycle related to fossil-fuel burning (N₂ burned to NOx).
Sulfur cycle- virtually no elemental S in air (there are other S compounds in air), but also essential
       to plants; Imbalance in S cycle related to fossil-fuel burning (S in fuel to SO₂)
Book titled “The Population Bomb” by Paul Ehrlich; Thomas Malthus hypothesis of world population
      growth dating back to the early 1800s - world population will increase disastrously unless checked
      by war, famine and disease, or “moral restraint”.
 “Compounding”= building up of something on the basis of its rate of growth; for example, in a bank
     account money can earn interest at some annual rate by compounding.
Hypothetical population growth curve stages=> 1. lag, 2. exponential, 3. stationary, 4. death
“Carrying capacity”= optimum population that can be sustained, and depends on natural
      resources (incl. food), energy, waste, interactions)

"Rule of 70”= you can determine how long it will take to double by dividing the annual rate of
          increase into 70.  For example, a city whose population is increasing 7% per year will
         double its population in 10 years (70/7 = 10)
Population and rates of growth on different continents.
Population density (number of people per unit area) is greatest in Japan, Asia and Europe;
         lowest in Australia.
Energy use per capita (per person) is highest in US, Europe, Former Soviet Union, Japan.
        Related to Kyoto Protocol, calling for developed nations (primary energy users) to cut
        back their CO₂ input to the atmosphere to 1990 levels; but developing countries (China,
        India) are not expected to do so.
Characteristics of populations (these can influence the trajectory of population change): birth rate,
       death rate, sex ratio, age distribution of populations, dispersal (emigration immigration)
ZPG (zero population growth); US is approaching it but ZPG has not been reached because of
       (1) death rate is falling because of improved health services, (2) about 1million people
       immigrate to US per year, (3) still many people in pre-reprodocutive and reproductive
      age groups.  If fertility rate went to 2.1 children per woman, the population would
      achieve ZPG more rapidly.
Population trends (from UN Report-world increasing 1.2% per year currently; life expectancy
      is increasing in both developed and developing nations (World Population Prospects, see
      the 2002 Revision highlights at: http://www.un.org/esa/population/unpop.htm
Consequences of Industrial (developed) society, good and bad- food availability, transportation
      (cars), move to suburbs from central urban areas, energy-saving gizmos, 5% of world
      uses 1/3 of world power, pollution

Major mechanism of land-use change is deforestation
First forests in Devonian, but perhaps largest past forests (300-350 my ago [Carboniferous],
         40-100 my ago [Cretaceous]; evidence found in coal beds
Climate can affect type and distribution of forests, (for example “cold”[icehouse] periods of last
         4.5 billion years alternated with longer warm periods, and in the last 150,000 years there
          has been about 10°C change in temperature from interglacial periods 135,000 years ago
          [and now] versus conditions during the cold glacial “maximum” at 20,000 years ago).
          The warm conditions 65 my ago promoted expansion of the recently evolved temperate
          forests, and ice ages resulted in shifting of forest southward in N. America and Europe,
         and back northward over the past 20,000 years
Modern forests- 4-5 billion hectares world wide, estimates vary depending on definitions of
         forests and woodlands;
50% of tropical forests (S. America, Asia, Africa) have been cut in last 200 years, ie, very rapid
        deforestation (India, Indonesia, Brazil have greatest deforestation; Japan, USA and Singapore
        are biggest importers of tropical wood); tropical forests may have distinct wet/dry seasons
         related to the position of the ITCZ; tropical forest characterized by great biodiversity, including
        diversity with height; a genetic “storehouse” possibly containing many new compounds that
        could become cures and treatments for out illnesses and ailments (“Tropical Pharmacy”);
        about 30% of all terrestrial NPP; contains 1/3 of all carbon in terrestrial biomass, but soils
        only contain a small fraction (4%) of all carbon in soils world-wide; very tight nutrient cycling
        and retention promoted by mutualistic fungi, dense canopy that inhibits erosion, leguminous
        (N-fixing) trees

Quiz 4; Stage 2 of Writing Project was handed in; in-class writing exercise (abstracts)
The “missing sink” problem (maybe better called the “unidentified sink(s)” problem)=> about 6-6.5 GtC
        are going into atmosphere from fossil fuels per year + another 1-1.5 GtC from land-use change
        (largely Amazon deforestation) =7-8 GtC total;  HOWEVER, we can only account for sinks for
        this excess carbon of about 3.5 GtC in the atmosphere (about 50-60% of the fossil-fuel carbon release)
        + 2.2 GtC in oceans by inorganic dissolution=5.7GtC.  So where is the rest of the carbon (1.3-2.3 GtC)
        going, ie, what is the "missing sink"? There must be natural "sinks" for CO₂ that have taken it up
        (for example biological uptake in oceans); a large amount of research money and effort is going to
        identifying and understanding those sinks.
One additional possibility is that humid Tropic forests themselves are a sink for C.  An inventory study by
        Phillips and others (1998) looked at the change in basal area (a surrogate for biomass) of mature tropic
        trees in “permanent” plots located in Neotropical and Paleotropical forests over the past 30-40 years. 
        They found a decrease in biomass in Paleotropic trees that may not be significant because the number
        of sample plots was so small, but a large increase in Neotropical trees, consistent with a sink of 0.6 GtC
        per year.  Humid tropic forests could therefore be a major contributor to the “missing sink(s)”.

Stage 2 of writing project returned along with numerical grade and comments. Final Stage 3 is
            due on Friday, April 25, consisting of ALL of the following, improved as indicated in
            comments:
      A. a revised paper including- revised positives and negatives, revised title, revised text of
            your essay/paper, revised references
      B. the Stage 2 paper with grade and comments
      NOTE: as you revise, consider that only about 50% of what was wrong with your paper was
            probably caught this time around, so you are responsible to make the indicated changes
            and also find anything else that poor or incorrect and correct that.
Group Activity 4 results discussed- Economist won 26 out of the bet in the class groups.
Group Activity 5 previewed- Developing a plan to reduce our influence on radiative forcing.
Handout with tips on writing good paragraphs
Soil Degradation
          1.    Soil Erosion (57% by water, 29%by wind) in US this is erosion averages about 10
                tons per hectare
                Consequences: A- loss of fertile soil (reduced production; more runoff; less water
                storage in soils; soil harder to till  B- impacts on surface water (higher flood levels;
                reservoirs can fill in with sediments; turbidity (muddiness) can impact aquatic life) 
               Wind can abrade leaves and expose roots
          2.     Physical (2-3%) excessive compaction, waterlogging)
          3.    Chemical (12%) salt build-up; stripping of nutrients; excess fertilizers;
                pesticides/herbicides; wet/dry deposition (acid); industrial wastes/spills
Changes in erosion related to land-use change (example the Washington DC area)

Quiz 5, first 20 minutes; answered questions about stage 3 of writing project due on Friday
GA5 make-ups= Wed 12:55pm room 330 Space Sciences; Thur 4pm room 104 W. Stadium
Anthropogenic causes of soil degradation- overgrazing, deforestation, agricultural practices,
           fuelwood gathering, industrial & waste pollutants
Water perturbation/degradation
           Water requirements for a western society (household, agriculture, industry);
            world-wide use of water domestic/irrigation/industry); above and belowground water
            resources; hydrologic subdivisions; water supply and “withdrawal” (total water
           withdrawn) vs. “consumption” (portion of withdrawal not immediately returned to
           source- lost to evaporation, transpiration, crops, products, humans)
“Thought” demonstration of porosity with “sand” and water-- about 40% of the 150 ml of sand is
           empty space that could be filled with water; this is equivalent to an aquifer in which a large
           volume of water is being held in the “pore” spaces between mineral grains.

Stage3 writing project turned in; end-of-semester lesson on where Prof. Leavitt’s office is.

Western Water problems including demand, evaporation exceeding rainfall requiring irrigation for agriculture, chemical pollution from pesticides/fertilizers/ herbicides, pollution from landfills, pollution from industry (such as TCE in Tucson), groundwater “mining” (and cone of depression of water table), land subsidence, and salinity build-up in soils. 

Primary pollutants (directly out of the smokestack or tailpipe): such as VOCs (volatile organic compounds), nitrogen oxides, sulfur oxides, carbon monoxide (CO) and particulates; Sources dominated by transportation, power generation, industry [all primary pollutants derive from the fuel (for example coal can contain lots of sulfur), except for nitrogen oxides whose nitrogen derives primarily from air N₂]

Secondary pollutants (formed by transformations of primary pollutants frequently involving water, oxygen and/or sunlight): such as sulfuric acid (from sulfur oxides), nitric acid (from nitrogen oxide) and ozone (tropospheric ozone the product of interaction of nitrogen oxides, VOCs and sunlight)

Catalytics converters target CO, VOCs and NOx.  Emissions testing of automobiles commonly meaures VOCs (unburned hydrocarbons) and CO.

Acid rain: pH scale; acid rain often defined when pH<5-5.2.  The pH when background atmospheric CO₂ dissolves to form weak carbonic acid is about 5.5-5.8, and sometimes other natural acids including organic acids can make the pH a little lower; thus rain from “clean” areas is slightly acidic); eastern US emissions dominated by sulfur dioxide whereas western US emissions much more related to nitrogen oxides