Natural Hazards Climate and Climate Change Chapter 12.
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Transcript of Natural Hazards Climate and Climate Change Chapter 12.
Natural Hazards
Climate and Climate ChangeChapter 12
Learning Objectives Understand the difference between climate and
weather, and how their variability is related to natural hazards
Know the basic concepts of atmospheric science such as structure, composition, and dynamics of the atmosphere
Understand how climate has changed during the last million years, through glacial and interglacial conditions, and how human activity is altering our current climate
Learning Objectives, cont. Understand the potential causes of climate
change
Know how climate change is related to natural hazards
Know the ways we may mitigate climate change and associated hazards
Climate and Weather
Weather = short periods of time.
Climate = a long period of time.
Climate zones Defined using Koeppen System
Uses monthly average temperature and precipitation
What information is provided in a climograph?
Climographs - Annual Temperature and Precipitation
Notice that in the southern hemisphere June and July are coldest months.Notice that in the northern hemisphere
June and July are warmest months.
Notice that some places have a DRY season.
The United States exhibits all of the major world climate zones
E = Polar
D = severe continental
C = mild
B = dry
A = tropical
H = mountains
Koeppen’s Classification System A-tropical, temp>18oC (64oF) year round
B-Dry, evaporation > precipitation
C- Mild Mid-latitude, 18oC (64oF)>coldest month> -3oC (27oF)
D- Severe Mid-latitude, coldest month< -3oC (27oF)
E – Polar, temp < -3oC (27oF) year round
H-Highland, Mountain areas
C mild Marine West Coast
C mild coastal
Mediterranean
ATropical
Allred’s climate zone summary for the United States
B cold
B hot
D cold-wet
Cwarmwet
E Polar
H mountains are mostly in the western
United States
Hawaii also has tropical “A”
Atmospheric Conditions
Permanent gases
Variable gasesGases whose proportions
CO2 is now above 400 ppm
Water is key to everything else.
Permanent Gases
Nitrogen, oxygen, and argon
About 99% of the atmosphere
Relatively unimportant to atmospheric dynamics
Permanent Gases
Nitrogen in the air is mostly inert. However, if you put energy into making nitrogen compounds, you can get that energy back later:
FertilizerRocket fuel Explosives
Oxygen is largely inert until it ‘oxidizes’ other elements and compounds, creating powerful, variable atmospheric gases.
Humans create far more variable gases than nature needs to maintain earth stability.
Oxygen is also relatively inert as an atmospheric component.
However, oxidation combines oxygen with carbon, nitrogen and many other elements to produce molecules that are complex, reactive and important.
Are combustion, fire and explosion forms of oxidation? <Yes.>
Consider the variable gases that result.Next page
Variable Gases – Carbon Dioxide (CO2)
Extremely important, but still only about 400 parts per million in the air
Released naturally by volcanic activity, plant and animal respiration, decay of organic material.
Released unnaturally by anthro (human) processes.
Don’t forget the carbon monoxide also results from combustion and is a genuine poison.
Variable Gases – Carbon Dioxide (CO2),
Anthropogenic (human) sources Burning of fossil fuels increases CO2 . Deforestation means that excess CO2 not removed.
Atmospheric levels are increasing by 2 ppm per year.
Soil and oceans may be reaching their limits in how much CO2 they can absorb.
Let’s look at variable gases – starting with water vapor
Water processes are a solar energy function
Water vapor is humidity created by evaporation
Storing energy in the atmosphere as vapor is an efficient way to move energy and provoke vast earth changes and life processes.
Storing heat as water vapor is also a source of energy for violent storms.
.
Ice contains substantial heat energy.
Water vapor contains dangerous
amounts of latent heat
Liquid water contains a lot more heat
Variable Gases – Ozone O3
Forms when atomic oxygen (O) collides with oxygen molecule (O2) – ozone is produced by collision with incoming ultraviolet solar energy.
Mostly found in stratosphere
Acts as a shield for ultraviolet light and is essential to life on earth
Chlorofluorocarbons (CFCs) partially destroyed ozone shield Increases skin cancer, cataracts, caused local crop failures
Ozone is also created by sunlight interacting with oxides of nitrogen and sulfur.
True or False?
1. If human activity can reduce the earth’s ‘ozone layer’ then doing so should help make the surface of the earth warmer.
2. A small increase in ocean temperature represents a vast increase in energy.
3. A small change in atmospheric gases can warm the atmosphere and the ocean beneath.
Consider current Salt Lake area news: The Stericycle company uses high heat to kill pathogens in medical waste.Neighbors want the waste management plant shut down.
Questions:
1. Does burning waste contribute to climate-changing greenhouse gases?
<yes>
2. Can the process simply fail at times -- releasing excess air pollution?
<yes>
3. Does high heat reduce halogens (chlorine, fluorine, bromine-based chemicals), heavy metals and other toxins, such as radio-active isotopes?
<many toxic substances are not destroyed by fire>
4. If Uv and Ozone are dangerous, then can they be used to sterilize food and kill pathogens?
<yes>
Variable Gases – Methane (CH4) Primary constituent of natural gas
Occurs naturally from bacterial decay, intestinal tracks of termites, cows, and sheep
Anthropogenic sources: coal mines, oil wells, leaking natural gas pipelines, rice cultivation, landfills, and livestock
Levels have doubled since 1700 and is a significant contributor to warming
Methane is more than 20 times per unit more powerful than CO2 as a ‘greenhouse’ gas.
Variable Gases – Oxides of Nitrogen (N2O, NO2, NO, etc.)
Nature makes some oxides of nitrogen through wildfires, ocean waves and soil building.
Human sources include fertilizers and burning fossil fuels.
Contributes to atmospheric warming.
N2O is also “laughing gas” at the dentist’s office and dragster racing fuel.
Variable Gases – Halocarbons Chemical compounds containing halogen elements
bonded with carbon
Include CFCs and are almost entirely anthropogenic
Used in industrial processes, fire fighting, and as fumigants, refrigerants, and propellants
Contribute to warming in troposphere and ozone depletion in stratosphere
Halocarbons are extremely useful, inexpensive and not particularly toxic when in appropriate use. Replacements are less competent and cost more.
Aerosols (microscopic particles including ice)
Provide surfaces that help water vapor condense back to liquid – rain/snow may not occur without a place to go.
Associated with air pollution
Natural sources: desert dust, wildfires, sea spray, and volcanoes
Human sources: burning of forests and fossil fuels
Aerosols can be dense enough to cool the earth by screening out solar energy.
Aerosols
During a drought “rain makers” might throw dust in the air to provide ‘condensation nuclei’
How does that process compare to what your car is doing right now in the parking lot?
On “911” when airliners were grounded, the absence of vapor contrails allowed the earth to warm-up by about one degree.
Rain sometimes occurs after bomb blasts toss dust and smoke into the air.
Montreal Protocol (banned CFCs – ozone layer is slowly repairing itself)
Kyoto Protocol(tries to limit CO2 but has not been fully ratified CO2 is still increasing in the atmosphere)
Structure of Atmosphere, revisited Defined by changes in
air temperature
Troposphere is where weather happens
Stratosphere dry, cold layer Little weather occurs
here Strong winds circulate
aerosols
Atmospheric Circulation Responsible for location of climate zones
At equator, warm air rises towards poles
Dry air descends near 30o North and South latitude Descending air produces high pressure and low rainfall
High pressures at North and South Poles – dry/cold dense air
Mid-latitude storms are the ‘battleground’ between the dry heat of deserts to the south and polar deserts to the north.
Mid-latitudes host the world’s most violent storms and the most people.
Pleistocene Epoch Multiple ice ages
Glaciers covered 30% of Earth (today 10%)
Maximum extent 21,000 years ago
Global sea level >100 m (330 ft) lower than today
The Greenhouse Effect
Earth’s temperature depends on three things:1. Amount of sunlight received – variations in
solar flow
2. Amount of sunlight reflected
3. Degree to which the atmosphere retains heat• Water vapor, carbon dioxide, methane, nitrous oxides,
and halocarbons absorb IR radiation• Gases act as “blanket” to retain heat in troposphere
Key factor: mostly shortwave solar energy gets in easily. Once converted to mostly long wave energy, it is harder to get back out. Over-warming happens rather easily.
How solar energy enters the atmosphere and then leaves
See simplified version next page
We can simplify the earth’s “solar budget”
For each 100 incoming: 31 reflected back out 69 absorbed:
- 45 by land and water- 21 by the atmosphere- 3 by the ozone layer
How much leaves quickly by longer-wave radiation? <69>
Total for atmosphere = about 24 percent
69 total absorbed
The “Greenhouse Effect” is vital to keep the earth at a healthy temperature
(average 59°F)
However, human air emissions appear to be making the earth too
warm:
CO2, CO, CH4, Nox, Sox, O3.
Carbon Dioxide and The Greenhouse Effect
Carbon dioxide accounts for most of human-caused greenhouse effect.
Air Temperature and Carbon Dioxide Notice that air temperature varies with carbon dioxide in the atmosphere – more CO2 => more heat
Atmospheric Carbon Dioxide Concentrations
Burning fossil fuels raises world CO2 concentration exponentially.
Human industrial age
Atmospheric Carbon Dioxide Concentrations, cont.
CO2 levels go down in summer when plants absorb it.
CO2 goes up in winter when plants are dormant and humans continue to drive cars and run power plants.
Global Temperature Change–Last 140 Years 1750, warming trend begins until 1940s. 1910 to 1998, global temperatures rise. Temperatures in past 30 years are warmest since
monitoring began.
Volcanic Forcing Ash from eruptions becomes suspended in the
atmosphere, reflects sunlight having a cooling effect.
Mount Tambora, 1815 eruption contributed to cooling in North America and Europe.
Mount Pinatubo in 1991 counterbalanced global warming during 1991 and 1992.
Effects of Climate ChangeNovember 11, 2013 New York Times article on concerns in Miami and environs. High-tide flooding.
Desertification and Drought Climate change increases human induced
conversion of land to desert
Causes soil and natural vegetation degradation Long-term loses for agriculture and grazing
Increase in drought events
Wildfires may become more common and more violent
As the atmosphere gets warmer
Sea level should rise.
In a sense, Geography 1700 is not as much about the earth as it is about how people think, wherever they are.
Systematic thinking is helped by systematic visualizing.
Consider two ‘climate change’ problems:
Problem 1. The sequence of building a thunderstorm.
Problem 2. The sequence of atmospheric gas interaction.
Step 1: The Big Six
Characteristics of the
Atmosphere (and sequence)
Air temperature Air pressure Wind Humidity Cloudiness Precipitation
Problem #1: The Sequence of building a thunderstorm
Step #2 Storms are a SOLAR Process
Air warmsWarming air expands pressure Pressure windWind and heat evaporate waterVapor is latent heat hidden in humidityWarm vapor is light-weight risesRising air decompressesDecompressing air cools by expansionCooling leads to saturation condensation – vapor goes to liquid Liquid precipitates rain, snowWith enough heat, the process repeats and builds
Anything that alters the atmosphere to retain more heat will lead to more energy for:
- severe storms- drought- rising sea levels
Example #2 – Climate Change is About Atmospheric Warming
1% Variable Gases include greenhouse’ gases (GHG) that keep the earth warm.
More GHG more earth warming
More warming more evaporation
more energy for storms
bigger deserts
more heat worsens smog
99% Permanent Gases – neutral (except as plant food)
Humans burn fossil fuel adds more oxides of carbon
and oxidizes nitrogen and sulfur
smog (Nox, Sox)
Sunshine and Nox, Sox ozone (more smog)
“Bottom Line”?
Burning fossil fuels returns vast amounts of ancient “stored sunshine” back into the atmosphere, promoting:
- More heat- More acidity- Air pollution
Even neutral nitrogen gets pulled into the fire and converts to more acidic oxides and more ‘smog.’
Sunshine then combines with smog oxides to produce more ozone.
What is the “Ozone” story?
Atmospheric ozoneis made naturally in the stratosphere by Uv colliding with oxygen.
That process absorbs 95% of dangerous Uv.
Man-made CFCs destroy atmospheric ozone.
Ground-level ozone is made by natural & human processes.
Nasty stuff.
Solution: Humans have banned CFCs, but we still produce vast quantities of hazardous ground-level ozone.
Excessive ozone is the #1 reason for Utah air-quality alerts.
Bicycles are the answer.