Earth Science, 11e

Climate Change & Air Pollution

Chapter 20

The climate system

Climate is an aggregate of weatherInvolves the exchanges of energy and

moisture that occur among the • Atmosphere• Hydrosphere• Solid Earth• Biosphere, and• Cryosphere (ice and snow)

World climates

Every location has a distinctive climateThe most important elements in a climatic

description are • Temperature, and• Precipitation

Climate classification Brings order to large quantities of

information Many climatic-classification systems have

been devisedKöppen classification of climates

• Best known and most used system• Uses mean monthly and annual values of

temperature and precipitation

Human impact on global climate Humans have been modifying the

environment over extensive areas for thousands of years• By using fire• By overgrazing of marginal lands

Most hypotheses of climatic change are to some degree controversial

Human impact on global climate Global warming

• Water vapor and carbon dioxide absorb heatand are largely responsible for the greenhouseeffect of the atmosphere

• Burning fossil fuels has added great quantitiesof carbon dioxide to the atmosphere

-> Global Warming Lecture

Energy consumption in the United States, 2001

Figure 20.15

Air Pollution and Acid Rain• Combustion: the rapid chemical reaction (burning) of a fuel

(energy-rich substance) with oxygen

• Fossil fuel: the energy-rich hydrocarbon remains of ancient fossil plankton that gathered sunlight energy, including coal, natural gas, and oil (petroleum)

• Pure carbon when burned creates carbon dioxide as a waste gas. However, most fuels are hydrocarbons with naturally-occurring inpurities, such as sulfur

• Sulfur is naturally found as sulfate in most bituminous coal deposits; when burned, sulfur dioxide gas is released

Air Pollution and Acid Rain• Sulfur dioxide gas released from burning high-sulfur coal

mixes with rain water to create sulfuric acid (acid rain)

• Sulfur dioxide can cause significant corrosion of metal and building stones in public buildings

• EPA regulates sulfur dioxide emissions under the Clean Air Act. Industrial plants installed electrostatic scrubbers to remove sulfur dioxide from their smoke stacks

• Low-sulfur (freshwater) coal was eventually substituted for high sulfur coal, and most scrubbers were abandoned, and domestic coal demand collapsed.

• Nitrous oxides from combustion produce nitric acid.

Acidified Little Rock Lake (northern Wisconsin)

Acid Rain: Legacy of Factories Burning Coal for Decades

• Coal burning had been powering factories since the Industrial Revolution dating back to the early to mid 1800’s, creating acid rain

• Acid rain brought by prevailing winds (west-to-east) has caused highly acidified lakes that are clear from top to bottom; the pH is so acidic that not even algae can survive

• The impact of decades of acid rain (better known as acid precipitation) is causing North American lakes to turn to jelly.

• In 1987, six states in the northeast filed a lawsuit against the U.S. federal government over the environmental damage caused by acid rain and the EPA’s lack of regulation.

Acid Rain: Legacy of Factories Burning Coal for DecadesThe impact of decades of acid rain (better known as acid precipitation) is causing North American lakes to turn to jelly.

Understanding the pH ScaleThe pH scale is logarithmic (orders of 10), going from the strongest acids (zero pH) to the strongest bases (alkaline) at 14. Pure distilled water has a pH of 7.0. Coca Cola has pH of 2.52.

The pH range of most aquatic environments is from 6.5 to 8.2

The pH range of most aquatic environments is from 6.5 to 8.2

The pH range of most aquatic environments is from 6.5 to 8.2

Human impact on global climate The atmosphere response

• Global temperatures have increased • Balance of evidence suggests a human influence on

global climate• Globally averaged surface temperature is projected

to increase by 1.4 to 5.8ºC by the year 2100• The role of trace gases

• Atmospheric trace gasses • Methane• Nitrous oxide• Certain chlorofluorocarbons

Annual average global temperatures variations for the

period 1860-2001

Figure 20.17

Annual average global temperatures variations for the period 1850-2019

Human impact on global climate The atmosphere response

• The role of trace gases• Absorb wavelengths of outgoing Earth radiation• Taken together, their warming effects may be nearly

as great as carbon dioxide

Climate feed-back mechanisms Possible outcomes of altering the climate-

system Two types

• Positive -feedback mechanisms reinforce the initial change

• Negative-feedback mechanisms produce results that are just the opposite of the initial change and tend to offset it

Some possible consequences of global warming

Altered distribution of the world’s water resources and the affect on the productivity of agricultural regionsRise in global mean sea level Changing weather patterns

• Higher frequency and intensity of hurricanes • Shifts in the paths of large-scale cyclonic

storms• Changes in frequency and intensity of heat

waves and droughts

End of Chapter 20