1. Global Climate Change

3. 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

4. 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?

5. 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!

7. 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.

8. Web-based Animations of the Greenhouse Effect

9. Sun and Earth Spectra

10. 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

11. CO2 and CH4 Molecules
The two most important greenhouse gases!

12. Molecular response to different types of radiation
Greenhouse effect
Ozone
Cooking

13. Molecular Vibrations of CO2

15. Trends in Global Temperature
ISAT 112
Red dots represent increases in temperature during

16. 1997
1995
1998

17. 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.

18. Temperature Trends

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

20. 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.

21. Comparison of Greenhouse Gases
Gas Factor Abundance% Impact
CO *10-2 1
CH *
N2O *
O *
CCl2F2 25, *
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!

23. CO2 Measurements - Hawaii
2010: ppm
CO2 Measurements - Hawaii
2005: ppm

25. Collecting glacial ice cores

26. 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.

27. 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.

28. The carbon cycle

29. 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

30. 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

31. 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,

32. Mass Percent CH4 + 2 O2  CO2 + H 2O # Moles = 1 2 1 2
Grams = =
Grams C =
% C 12/ /44
75% %

33. 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
= 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) = g S/ g SO2
(0.501 g S/ g SO2) x 100% = 50.1 % Sulfur
(28.0 g N/ 44.0 g N2O) = g N/ g N2O or % N
YT 3.15
a. 19 mmt SO2 x g S/ g SO2 = 9.5 mmt S
b mmt SO2 x mmt S/ mmt SO2 = mmt S 33

34. 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. (
The average global temperature will continue to rise as emissions of anthropogenic greenhouse gases increase.

35. 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)

36. 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.

37. 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

38. Sources of CO2
Fig. 3.17

39. 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.

40. Practice problems
NaOH
CaCl2
MgCO3
Al2(PO4)3
C3H8

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

43. Fig. 3.23

44. Fig. 3.23a

45. Fig. 3.23b

46. 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?

47. 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 = lb CO2/gal gas

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

49. Fig. p.115

51. 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?