Chapter 4 -Climate change What are the sources of carbon on Earth? How does carbon move between reservoirs, and how do scientists measure this? What are “greenhouse gases”, and what are their positive and negative effects? What are the global consequences of climate change? How do today’s climate trends differ from the past? How do my daily actions affect the global environment?

Importance of Carbon Carbon is one of the most important elements on Earth. Carbon atoms are central to such processes as combustion, photosynthesis, cellular respiration, and sedimentation. Carbon atoms are rarely found in their elemental form. They are generally found in molecular and ionic compounds.

Carbon, Carbon Everywhere! Carbon atoms are always on the move, moving from one reservoir to another. Reservoirs – places where carbon atoms are found. Carbon atoms are in the atmosphere (CO2, CO, CH4), as carbonate minerals in rocks, and in plants and animals (proteins, carbohydrates, lipids). Three main reservoirs: The atmosphere Rocks Plants and animals

Understanding the Carbon Cycle Which processes add carbon atoms (CO2) to the atmosphere? Which processes remove carbon atoms from the atmosphere? What are the two largest reservoirs of carbon atoms? Which parts of the carbon cycle are most influenced by the activities of humans?

Respiration adds CO2 to the atmosphere; photosynthesis removes it.

Ionic Compounds The carbon atoms found in rocks are generally part of an ionic compound. Ionic compounds metal bonded with nonmetal. Formed from positive ions (cations) and negative ions (anions). Metals lose electrons (+); nonmetal gain electrons (-). Overall electric charge on the compound is zero. Rules for nomenclature – p. 121 – 123.

Nomenclature and Chemical Formulas Write the names and chemical formulas for each of the following. a. Ca and S b. Mg and O c. F and K d. Cl and Al

Writing Chemical Formulas When writing chemical formulas for ionic compounds, you must pay attention to the charges (oxidation numbers) of individual ions that make up the compounds. Remember, individual ions are charged; but, the compound as a whole is neutral and chemical formulas must indicate this. To write a formula correctly we use the “criss-cross” method, where charges of the ions are crossed over and become subscripts for their counterparts. Examples: Calcium chloride Magnesium oxide Aluminum sulfide ***Always simplify/reduce subscripts to lowest terms for ionic compounds.***

Nomenclature and Chemical Formulas Write the names and chemical formulas for each of the following. a. Mn and O b. Ag and N c. Cu and S d. Sn and O

Polyatomic Ions Polyatomic ions – two or more atoms covalently bonded together that have an overall positive or negative charge. Example – the carbonate anion, CO3 Calcium carbonate is the ionic compound commonly known as chalk and found in the rock portion of the carbon cycle. Table 4.1 – p. 123

Nomenclature and Chemical Formulas Write the names and chemical formulas for each of the following. a. Na and SO4 b. Al and C2H3O2 c. OH and Mg d. CO3 and K

Chemical Formulas Write the correct chemical formula for the following. a. sodium hypochlorite b. magnesium carbonate c. ammonium nitrate d. calcium hydroxide

Molar Mass of Compounds Molar mass – the total mass of all the atoms that make up a specific compound. CO2 = 44.01 g/mol C = 1 X 12.01 = 12.01 O = 2 x 16 = 32 12.01 + 32 + 44.01g/mol Percent composition – the amount in percent of any given element within a compound. Carbon dioxide is 27.3% carbon. 12.01g x 100 = 27.3% 44.01g

Molar Mass and Percent Composition Practice Determine the percent composition of each of the following compounds. Potassium sulfate Ethanol, C2H5OH Calcium nitrate Aspirin, C9H8O4 Ammonium carbonate

Understanding the Carbon Cycle and Its Relation to the Amount of CO2 in the Atmosphere The carbon cycle is a dynamic system, consisting of both natural addition and removal mechanisms. For example, respiration adds CO2 to the atmosphere while photosynthesis removes it: Respiration: 6 CO2 + C6H12O6 → 6 CO2 + 6 H2O Photosynthesis: 6 CO2 + 6H2O → 6 O2 + C6H12O6

Human Activities in Relation to the Carbon Cycle Anthropogenic activities rely on processes that put more carbon atoms into the atmosphere rather than on those that remove them. For example, the burning of fossil fuels (combustion)for electricity, transportation, and heating all transfer carbon atoms from the largest underground carbon reservoir into the atmosphere. Human activities also influence CO2 emissions by clear-cutting and slash-and-burn practices which remove large amount of trees from the environment. Trees are very efficient absorbers of CO2 but are removed from the carbon cycle through deforestation.

Global Carbon Dioxide Emissions

Average Atomic Mass Average atomic mass – the weighted average of the atomic masses of naturally occurring isotopes of an element. The average atomic mass of an element depends on both the mass and the relative abundance (%) of the element’s isotopes. For example, naturally occurring copper consists of 98.93% carbon -12 and 1.07% carbon-13. The average atomic mass is calculated by multiplying the atomic mass of each isotope by its relative abundance (expressed in decimal form) and adding the results. (12)(.9893) + (13)(.0107) = 12.01 amu

Quantifying Carbon – Molecules and Moles Mole - the number equal to the number of carbon atoms in exactly 12 g of pure C-12. Atomic number 1 mole = Avogadro’s number = 6.022 x 1023 Mass number A mole of atoms of any element has a mass (in grams) equal to the atomic mass of the element in amu.

One mole of carbon has a mass of 12.01 grams. 1 mol C = 12.01 g If you have 36.0 g of carbon, how many moles is that? 1 mol C 36.0 g C x = 3.00 mole C 12.01 g C

The critical link between moles and molecules is Avogadro’s number. Keep these relationships in mind: use molar mass use Avogadro’s number grams molecules moles Remember – the critical link between moles and grams of a substance is the molar mass. The critical link between moles and molecules is Avogadro’s number.

Making the Connections How many grams of CO2 are in 6.02 x 10 23 molecules of CO2?

Climate Change 1. What is it? 2. Can anything be done about it? 3. Is there really cause for alarm? 4. How can we assess the information from the popular press?

Why Does it Matter Where Carbon Atoms End Up? Now that we can quantify the amounts of carbon in different reservoirs, we can look at what effect carbon-containing material can have in these reservoirs.

Earth’s Energy Balance Greenhouse effect The largest percentage of energy from the sun comes to Earth in the form of infrared (IR) radiation. Atmospheric gases trap and return a major portion of this heat radiating from the Earth. It is a natural, necessary process. Without this process, Earth would be frozen (0°F) and uninhabitable.

Greenhouse Gases Greenhouse gases (GHGs) – those gases capable of absorbing and emitting IR radiation, thereby warming the atmosphere. Water vapor Methane, CH4 Carbon dioxide, CO2 Nitrous oxide, NOx Ozone, O3 Chlorofluorocarbons, CFCs – CCl3F, CCl2F2

Global Warming Potential Global Warming Potential (GWP) represents the relative contribution of a molecule of an atmospheric gas to global warming.

According to data taken at Mauna Loa, Hawaii since 1958, CO2 levels are on the rise.

Microscopic air bubbles in ice core samples from glaciers can be used to determine changes in greenhouse gas concentrations over time.

Comparing ice core data from Antarctica and Mauna Loa observations, the concentration of carbon dioxide appears to be increasing over time.

The Vostok ice core shows data going back 400,000 years, while other ice cores go back even further (the inset shows data from the figure above). The current concentration of atmospheric carbon dioxide is 100 ppm higher than any time in the last million years.

Average global surface temperatures have increased since 1880. The red bars indicate average temperatures for the year while the black error bars show the range for each year. The blue line is the 5-year moving average.

Global temperatures for 2006 (in oC) relative to the 1951–1980 average Global temperatures for 2006 (in oC) relative to the 1951–1980 average. The most dramatic changes have been observed in the higher latitudes (dark red areas).

The concentration of carbon dioxide (blue) and the global temperature (red) are well correlated over the past 400,000 years as derived from ice core data.

Review: How to draw Lewis structures 1. Determine the sum of valence electrons. Draw Lewis Structures for: O2 CH4 SO2 C2H4 SO42– CO H2SO4 N2 NO3– O3 Use a pair of electrons to form a bond between each pair of bonded atoms. Arrange the remaining electrons to satisfy octet rule (duet rule for H). 4. Assign formal charges. Formal charge = # of v. e. – [# of nonbonding e– + ½ bonding e–] Remember: Resonance, relative lengths, and bond order!

Representations of methane CH4 = molecular formula; does not express connectivity Structural formulas show how atoms are connected: Lewis structures show connectivity. This Lewis structure is drawn in 3-D Space-filling

Valence Shell Electron Pair Repulsion Theory Consider methane (CH4), where the central carbon atom has 4 electron pairs around it: A tetrahedral- shaped molecule has bond angles of 109.5o Four electron pairs as far from each other as possible indicates a tetrahedral arrangement.

Valence Shell Electron Pair Repulsion Theory The legs and shaft of a music stand are like the bonds of a tetrahedral molecule.

Valence Shell Electron Pair Repulsion Theory The 3-D shape of a molecule affects its ability to absorb IR radiation. Valence Shell Electron Pair Repulsion Theory Assumes that the most stable molecular shape has the electron pairs surrounding a central atom as far away from one another as possible.

The central atom (O) in H2O also has four electron pairs around it. The nonbonding electron pairs take up more space than bonding pairs, so the H-to-O-to-H bond angle is compressed. But unlike methane, two electron pairs are bonding and two are nonbonding (lone pairs). The electron pairs are tetrahedrally arranged, but the shape is described only in terms of the atoms present: water is said to be bent shaped.

We can use the VSEPR model to allow us to predict the shape of other molecules. Number of electron pairs around central atom Shape of molecule Bond angle 4 electron pairs, all bonding: CH4, CF4, CF3Cl, CF2Cl2 tetrahedral 109.5o 4 electron pairs, three bonding, one nonbonding: NH3, PCl3 Triangular pyramid about 107o 4 electron pairs, two bonding, two nonbonding: H2O, H2S bent about 105o Other predictions can be made based on other electron pair arrangements.

Now look at the central atom of CO2: Two groups of four electrons each are associated with the central atom. The two groups of electrons will be 180o from each other: the CO2 molecule is linear.

A Comparison of UV light and IR radiation UV light has sufficient energy to cause molecular bonds to break. Shorter wavelength (10 nm – 100 nm); higher frequency = higher energy.

Molecular geometry and absorption of IR radiation Molecular vibrations in CO2. Each spring represents a C=O bond. (a) = no net change in dipole – no IR absorption. (b, c, d) = see a net change in dipole (charge distribution), so these account for IR absorption.

The infrared spectrum for CO2 Wavelength (mm) - longer wavelength = lower frequency = lower energy

The infrared spectrum for CO2 When discussing GHGs, keep in mind that we are focusing on the amount of heat that is trapped, not released back into the atmosphere… think “blanket”. As IR radiation is absorbed, the amount of radiation that makes it through the gases back into the atmosphere is reduced.

Molecular response to different types of radiation

How Do Greenhouse Gases Work? Any molecule that has three or more atoms will be able to absorb IR radiation and behave as a GHG. CO2 molecules that absorb specific wavelengths of IR radiation may respond in different ways. Some hold the extra energy for a brief time, and then re-emit it in all directions as heat. Others collide with N2 and O2 molecules, and can transfer some of the absorbed heat to those molecules. Through both these processes, CO2 “traps” some of the infrared radiation emitted by Earth, thereby, holding it in the atmosphere and keeping our planet warm.

Factors Determining GHG Classification Molecule must have 2 or more atoms. Global potential warming number Molecular geometry of the molecule/compound Ability to bend/stretch with exposure to IR radiation.

Amplification of Greenhouse Effect: Global Warming What we know: 1. CO2 contributes to an elevated global temperature. 2. The concentration of CO2 in the atmosphere has been increasing over the past century. 3. The increase of atmospheric CO2 is a consequence of human (anthropogenic) activity. 4. Average global temperature has increased over the past century.

What might be true: 1. CO2 and other gases generated by human activity are responsible for the temperature increase. 2. The average global temperature will continue to rise as emissions of anthropogenic greenhouse gases increase.

Radiative Forcings - factors that affect the balance of Earth’s incoming and outgoing radiation. Negative forcings have a cooling effect; positive forcing have a warming effect.

Blue bands = predicted temperature range using natural forcings only Climate Models are used to predict annual global mean surface temperatures. Blue bands = predicted temperature range using natural forcings only Pink bands = temperature range with both natural and anthropogenic forcings

Models can also be used to predict future global temperatures. Black line = data for the 20th century Other lines = projected 21st century temperatures based on different socioeconomic assumptions

Intergovernmental Panel on Climate Change (IPCC) Recognizing the problem of potential global climate change, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) established the Intergovernmental Panel on Climate Change (IPCC) in 1988. It is open to all members of the UN and WMO. In 2007, the IPCC stated that scientific evidence for global warming was unequivocal and that human activity is the main cause.

Conclusions from the 2007 IPCC Report

Loss of Polar Ice Cap NASA Study: The Arctic warming study, appearing in the November 1, 2003, issue of the American Meteorological Society's Journal of Climate, showed that compared to the 1980s, most of the Arctic warmed significantly over the last decade, with the biggest temperature increases occurring over North America. Perennial, or year-round, sea ice in the Arctic is declining at a rate of nine percent per decade.

Loss of Polar Ice Cap As the oceans warm and ice thins, more solar energy is absorbed by the water, creating positive feedbacks that lead to further melting. Such dynamics can change the temperature of ocean layers, impact ocean circulation and salinity, change marine habitats, and widen shipping lanes.

Sea Level Rise Expansion of warm water and melting of land based ice could cause– Water levels to rise 18- 59 cm (0.6-1.9 feet) during this century storm surges of 6 meters (20 feet) accompanying tropical cyclones and tsunamis

Sea Level Rise Maldives- Indian Ocean Degradation and loss of 1/3 of coastal estuaries, wetlands, and coral reefs Disruption of coastal fisheries Flooding of Low-lying barrier islands and coastal areas Agricultural lowlands and deltas Contamination of freshwater aquifers Submergence of low-lying islands in the Pacific and Indian Oceans and the Caribbean Sea Level Rise Maldives- Indian Ocean

Loss of Biodiversity Melting of permafrost in tundra soils releases methane and carbon di oxide Loss of arctic tundra-reduce grazing lands for caribou Boreal vegetation would replace tundra

Some organisms will increase 30% of land–based plants and animals will disappear (temp change 1.5-2.5*C) What about Migratory animals Forests Some organisms will increase Insects, Fungi, Microbes Exploding populations of mountain pine beetles Destroy lodge pole pine forests

Climate Shift Regions of farming may shift Decrease in tropical and subtropical areas Increase in northern latitudes Overall food productivity would decrease because of less productivity soil Decrease in food production in farm regions dependent on rivers fed by snow melt Genetically engineered crops more tolerant to drought

Climate Change Will Threaten the Health of Many People Deaths from heat waves will increase Higher temperatures can cause Increased flooding Increase in some forms of air pollution, more O3 More insects, microbes, toxic molds, and fungi Norman Myers – 150 to 200 million environmental refugees in this century

One potential method for mitigation is CO2 sequestration.

(CO2, CH4, NO, HFCs, PFCs, and SF6) Kyoto Protocol – 1997 Conference Intergovernmental Panel on Climate Change (IPCC) certified the scientific basis of the greenhouse effect. Kyoto Protocol established goals to stabilize and reduce atmospheric greenhouse gases. Emission targets set to reduce emissions of six greenhouse gases from 1990 levels. (CO2, CH4, NO, HFCs, PFCs, and SF6) Trading of emission credits allowed.

A Cap-and-Trade System can be used to limit CO2 emissions.