ENVIRON 102 Chapter Notes - Chapter 8: Sulfur Dioxide, Sub-Saharan Africa, Forest Management
10 May 2018
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Chapter 8 Climate Change (all)
8.1 Long-Term Climate Patterns
The Pleistocene – The Last 2 Million Years: For nearly million years, Earth’s climate has cycled between
cold and warm periods.
Pleistocene epoch: time of alternating cold and warm periods (each period was 100,000 years)
o Caused by changed in Earth’s orbit changes in solar radiation
o Changes in ocean currents change the patterns of heat transfer
o Volcanoes that spew ash
o Changes in chemical composition of Earth’s atmosphere
Holocene – The Last 10,000 Years: Periods of warming and cooling have produced different climate
patterns in specific regions.
Holocene epoch: last 10,000 years of the Pleistocene period
Medieval Warm Period: last 1,000 years with significant climate variation
8.2 Measuring Global Warming
Measuring Recent Climate Change: Since the beginning of the )ndustrial Revolution, Earth’s atmosphere
has warmed significantly.
Scientists do not know how to measure average annual air temperature
o But it’s not necessary to know that
Scientists can study temperature variation in various regions in the world
o Find temperature anomalies – difference between each year’s average temperature and
benchmark
Global warming: increase in atmospheric temperature since the late 1800s (coincides with the
Industrial Revolution)
Causes of Natural Climate Variation: Temperature trends vary among regions and from year to year.
Regional variation
Land masses heat up more quickly than bodies of water
Temperature anomalies are higher over interior of continents
El Nino/Southern Oscillation (ENSO) in Pacific Ocean
o Consequence of changes in currents that affect temperature of water near ocean’s surface
o 3 to 8 year period, surface ocean temperatures cycle between warm and cold
o During cold part (La Nina) – upwelling of deep ocean water colder water on the surface
▪ Cause prolonged droughts
o Warm part (El Nino) – water warmed in western equatorial Pacific moves east, overriding
colder surface
▪ Feed thunderstorms and increase rainfall
Volcanic eruptions can influence global climate
o Addition of sulfur dioxide into atmosphere, which reflects the sun’s rays and cool the
atmosphere
8.3 Causes of Global Warming
The Greenhouse Effect: Some gas molecules trap heat radiated from Earth’s surface in the lower
atmosphere.
Greenhouse effect: trapping of heat in the troposphere
o Gases may trap infrared light radiated from Earth’s surface
o Captured light energy transforms into heat
Greenhouse gases: gases that efficiently trap heat
Air becomes warmer increase in ability to hold water vapor (increase in evaporation)
runaway warming (increasing levels of water vapor trap more heat)
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Carbon dioxide, methane, and nitrous oxide
o Methane released naturally from decomposition of vegetation by microbes and termites
and from digestive processes of various animals
o Nitrous oxide is a natural by-product of denitrification process
Human Impacts: Human activities have increased the abundance of several greenhouse gases in the
atmosphere.
Deforestation decreased the amount of carbon stored in trees and increased the amount of carbon
in the atmosphere
Domesticated animals increased methane in the atmosphere with their digestive processes
Until Industrial Revolution, human-caused greenhouse gases were miniscule because human
population was still small
Burning of fossil fuels: first coal, then petroleum and natural gas
o Combustion released carbon dioxide
Continued deforestation
Fires associated with deforestation add methane and nitrous oxide
Forest fires and burning of fuelwood and charcoal release solid particles called black carbon into
atmosphere
o Reduce reflectivity of surfaces they settle on and increased warming
CFCs absorb infrared light 10,000-20,000 times more efficiently than carbon dioxide
o CFCs were banned in the Montreal Accord of 1987
Global warming potential GWP: molecule’s long-term impact of atmospheric temperature
o (1) Capacity to absorb infrared light
o (2) Atmospheric residence time
o Carbon dioxide has the benchmark of 1
o Methane has GWP of 25
o Nitrous oxide has GWP of 296
o CFCs are from 1,300 to 13,000
The Keeling Curve
o Charles Keeling began making systematic monthly measurements of atmospheric carbon
dioxide in Hawaii
o Shows that carbon dioxide was increasing at a rate of 1-2 ppm a year
Sources of Greenhouse Gas Emissions: Heat-trapping gases are generated from a variety of human
activities.
Scientists express total greenhouse gas emission in term of carbon dioxide equivalents (CO2e)
Burning fossil fuels (coal and natural gas) to generate electricity
Industrial processes such as manufacture of concrete
Agriculture – methane and nitrous oxide emissions from livestock and the use of fertilizer
Industrialized nations – most emissions are from burning fossil fuels
Other countries – most emissions are from deforestation and agriculture
Emissions in developing countries are alarmingly high
8.4 Consequences of Global Warming
Drier and Wetter: Global warming is producing wetter conditions in some places and drought in others.
Effects of rising temperatures vary from region to region
Rainfall has increased in N. and S. America, and in most parts of Europe and Asia
Rainfall has decreased in sub-Saharan Africa, the Mediterranean region, and western North
America
Drought in sub-Saharan Africa affects food production
Debate about whether global warming is producing intense storms and hurricane (especially after
the devastation of Hurricane Katrina)
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find more resources at oneclass.com
Document Summary
The pleistocene the last 2 million years: for nearly (cid:884) million years, earth"s climate has cycled between. Holocene the last 10,000 years: periods of warming and cooling have produced different climate patterns in specific regions. Holocene epoch: last 10,000 years of the pleistocene period. Medieval warm period: last 1,000 years with significant climate variation has warmed significantly. Scientists do not know how to measure average annual air temperature. Measuring recent climate change: since the beginning of the )ndustrial revolution, earth"s atmosphere: but it"s not necessary to know that, find temperature anomalies difference between each year"s average temperature and. Global warming: increase in atmospheric temperature since the late 1800s (coincides with the. Scientists can study temperature variation in various regions in the world benchmark. Causes of natural climate variation: temperature trends vary among regions and from year to year. Regional variation colder surface: cause prolonged droughts, feed thunderstorms and increase rainfall.
