Global Climate Change

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!

Greenhouse effect

Our atmospheric gases trap and return a major portion of the heat radiating

from the Earth.

It is a natural, necessary process.

The Earth’s Energy Balance

http://www.planetguide.net/book/chapter_3/greenhouse_effect.html

Web-based Animations of the Greenhouse Effect

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

OzoneGreenhouse

effect Cooking

Molecular Vibrations of CO2

Trends in Global Temperature

ISAT 112

1995 1997 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!

Temperature Trends in U.S.

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 .035These 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 2005: 379.5 ppm

2010: 392.9 ppm

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

Collecting glacial ice cores

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 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)•Atmosphere 750

•Forests 610

•Soils 1,580

•Surface Ocean 1,020

•Deep Ocean 38,100

•Fossil Fuels–Coal 4,000–Oil 500–Natural Gas 500

Total, all sources 47,060

Causes of GG increase

• Increased combustion– 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.

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.

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

Fig. 3.17 Sources of CO2

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

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?