Global Climate Change

Learning Objectives Understand mechanisms by which global warming occurs Relate Lewis structures and molecular geometry to absorption of radiation Apply atomic weight and Avogadro’s number to molar mass and mole calculations Consider the national and global implications of a 2-6oC rise in Earth’s temperature Describe ways in which carbon dioxide emissions can be reduced Take an informed position with respect to issues surrounding global warming

Question of the Day Based on energy balance models, we would expect the average surface temperature of the earth to be only –18oC. However the temperature is actually about 15oC. Hmm…what gives?

The Greenhouse Effect Solar radiation reaches the Earth’s surface as UV and visible light Some is absorbed by the surface Some of this is then re-radiated as IR But some of the IR can’t get back out of the atmosphere, and is reflected back to the earth So the earth’s temperature is higher than you would otherwise expect – and we can live here!

The Earth’s Energy Balance Greenhouse effect Our atmospheric gases trap and return a major portion of the heat radiating from the Earth. It is a natural, necessary process.

Web-based Animations of the Greenhouse Effect http://www.planetguide.net/book/chapter_3/greenhouse_effect.html

Sun and Earth Spectra

Molecules: How They Shape Up Molecular shape will affect whether a molecule is a ‘greenhouse gas’ (GHG) Shape can be determined using Lewis Structures or molecular models Reminder: The most stable molecular shape is the one in which the bonding or nonbonding electron groups attached to any atom are as far from each other as possible Example: Water

CO2 and CH4 Molecules The two most important greenhouse gases!

Molecular response to different types of radiation Greenhouse effect Ozone Cooking

Molecular Vibrations of CO2

Trends in Global Temperature ISAT 112 Red dots represent increases in temperature during 1950-1999.

1997 1995 1998

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.

Temperature Trends

More Temperature Trends… Weihenstephen Brewery in Freising starts, 1040! Red is from thermometers.

Temperature Trends in U.S. Regional trends from base year [1950]. The cooler area in the southeast is thought to be from aerosol particles that reflect sunlight.

Comparison of Greenhouse Gases Gas Factor Abundance% Impact CO2 1 3.7*10-2 1 CH4 30 1.8*10-4 .145 N2O 160 3.1*10-5 .132 O3 2000 4.0*10-6 .22 CCl2F2 25,000 5.2*10-8 .035 These gases have the ability to capture outgoing IR radiation from the earth, absorb that radiation, and re-radiate it back to the earth. The greenhouse effect!

CO2 Measurements - Hawaii 2010: 392.9 ppm CO2 Measurements - Hawaii 2005: 379.5 ppm

http://www.esrl.noaa.gov/gmd/ccgg/trends/

Collecting glacial ice cores http://www.seed.slb.com/en/scictr/watch/climate_change/proxydata.htm

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.

The Vostok ice core goes back 400,000 years The Vostok ice core goes back 400,000 years. The current concentration of atmospheric carbon dioxide is 100 ppm higher than any time in the last million years.

The carbon cycle

Carbon Reservoirs Reservoir Size (Gt of Carbon) Total, all sources Atmosphere 750 Forests 610 Soils 1,580 Surface Ocean 1,020 Deep Ocean 38,100 Fossil Fuels Coal 4,000 Oil 500 Natural Gas Total, all sources 47,060

Causes of GG increase Increased combustion Deforestation Agriculture Industrial revolution Fossil fuels Deforestation Amazon rainforest = 4,224,905 football fields/yr 8 football fields/minute Agriculture Melting of permafrost

CO2 Emissions by Country: Total emissions since 1950 (b tons) Graphic from: Michael Glantz, “What Makes Good Climates Go Bad? … and … “Why Care?” USAEE/IAEE Meeting, 9-19-05.

Mass Percent CH4 + 2 O2  CO2 + H 2O # Moles = 1 2 1 2 Grams = 16 64 = 44 36 Grams C 12 0 = 12 0 % C 12/16 12/44 75% 27%

Quick Quiz Calculate the mass percent of S in SO2 32 + 16 + 16 = 64 (32/64) * 100 = 50% Calculate the mass percent of N in NO2 14 + 16 + 16 = 46 (14/46) * 100 = 30.5% If 142 million metric tons of SO2 are released per year by fossil fuel combustion, calculate the mass of sulfur released. (1 metric ton = 1000 kg) Atomic weights: N = 14.0 O = 16.0 S = 32.1 YT 3.14 a. (32.1 g S/ 64.1 g SO2) = 0.501 g S/ g SO2 (0.501 g S/ g SO2) x 100% = 50.1 % Sulfur (28.0 g N/ 44.0 g N2O) = 0.636 g N/ g N2O or 63.6 % N YT 3.15 a. 19 mmt SO2 x 0.501 g S/ g SO2 = 9.5 mmt S b. 142 mmt SO2 x 0.501 mmt S/ mmt SO2 = 71.1 mmt S 33

In a recent poll, 97% of climate scientists believe that this is true. What might be true: CO2 and other gases generated by human activity contribute to the temperature increase. In a recent poll, 97% of climate scientists believe that this is true. (http://www.sciencedaily.com/releases/2009/01/090119210532.htm) The average global temperature will continue to rise as emissions of anthropogenic greenhouse gases increase.

Projected future regional patterns of warming based on three emissions scenarios (low, medium, and high growth). Source: NASA Earth Observatory, based on IPCC Fourth Assessment Report (2007)

Temperature projections to the year 2100, based on a range of emission scenarios and global climate models. Scenarios that assume the highest growth in greenhouse gas emissions provide the estimates in the top end of the temperature range. The orange line (“constant CO2”) projects global temperatures with greenhouse gas concentrations stabilized at year 2000 levels. Source: NASA Earth Observatory, based on IPCC Fourth Assessment Report (2007) Temperature projections to the year 2100, based on a range of emission scenarios and global climate models.

Global Climate Change bottom line There is ample evidence that the Earth experiences (and we rely on) the “greenhouse effect” carbon dioxide is a “greenhouse gas” the temperature of the atmosphere has been rising over the past century the concentration of carbon dioxide is also rising, and correlates both to this increase in temperature and the use of fossil fuels What is debated is whether humans are causing these changes The Intergovernmental Panel on Climate Change (IPCC) has said yes for years, and the Kyoto Protocol was intended to address this

Sources of CO2 Fig. 3.17

Molecular Mass What is a molecule? How many molecules are there? Avogadro’s number: 6.02 x 1023 units/mole 12 grams isotope C12 = 1 mole Calculating molar mass: add the number of atoms of one type times its atomic mass plus the mass of the other atoms to get molecular mass.

Practice problems NaOH CaCl2 MgCO3 Al2(PO4)3 C3H8

Answers NaOH = 39.998 g/mol CaCl2 = 110.98 g/mol MgCO3 = 84.32 g/mol Al2(PO4)3 = 338.87 g/mol C3H8 = 44.094 g/mol

Fig. 3.23

Fig. 3.23a

Fig. 3.23b

One Gallon Gas = 20 lbs CO2 Is this right? What do we need to know to prove it? What is the basic formula for gasoline? What is its density? How much carbon is in the gasoline? What are the products of its combustion? What is the ratio of CO2 produced to carbon burned?

Analysis 8 pints/gal * 0.8 lb gas /pint = 6.4 lbs gas/gal C8H18 = 114 g/mol, 84.21% C 6.4 lb gas/gal * 1000 g/2.2lbs = 2910 g gas 2910 g gas * .8421% C = 2450 g C 2450 g C/gal * 44 g/mol CO2/12 g/mol C = 8983 g CO2/gal 8983g CO2 * 2.2lb./1000g = 19.76 lb CO2/gal gas

Carbon Cycle How do we impact this system? A major part of the cycle is photosynthesis and respiration.

Fig. p.115

Some Questions about Global Warming Does increased CO2 in the atmosphere really induce growth? Can forests and soils sequester enough carbon to offset anthropogenic sources? How much proof is needed to recognize and act on a problem like global warming? What should we/can we do at the individual level?