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The Earth System
Earth: An overview
4 main spheres Hydrosphere (hydro=water) Biosphere (bio=life) Atmosphere (gas, air) Geosphere (geo=Earth)
So far we have focused on the geosphere:
The Earth; age Pangea Structure Plate tectonics Rock cycle
Now we will study the Atmosphere Mixture of gases that surround Earth
There are 4 layers in the atmosphere that are divided based on their temperature gradient. troposphere, stratosphere mesosphere, thermosphere
4 Layers1) Troposphere – layer in which
we live; Weather phenomena (clouds) occur here. It’s elevation ranges from 0 to 10 km
2) Stratosphere – above troposphere; temperatures increase with altitude. This layer contains the ozone layer, which
protects us from harmful sunlight
What are the layers in the atmosphere? (cont…)
Mesosphere – coldest layer of atmosphere
Thermosphere – uppermost layer; temperatures also increases with altitude. This is where most small meteorites burn
up the location in the atmosphere that the
northern lights occur (aurora borealis)
Structure of the Atmosphere
Thermosphere
Mesosphere
Ozone MaximumStratosphere
Troposphere
Temperature
Energy in the Earth System
In the Earth system…
Energy Flows
Matter Cycles
Life Webs
Energy flows in waves
Energy flows, and is lost
Energy flows in the Universe
A hotter radiating body emits shorter wavelengths.
A cooler body emits longer wavelengths.
diagram
Notice only about 50% of the solar energy directed at the Earth penetrates to the surface. The rest was absorbed or reflected by the
atmosphere.
The Earth emits heat
Electromagnetic Spectrum
incoming outgoing
1. Shorter, high energy wavelengths hit the earths surface
2. Incoming energy is converted to heat
3. Longer, infrared Wavelengths hit greenhouse gas molecules in the atmosphere
4. Greenhouse gas molecules in the Atmosphere emit Infrared radiation back towards earth
78% nitrogen
20.6% oxygen
< 1% argon
0.4% water vapor
0.036% carbon dioxide
traces gases:Ne, He, Kr, H, O3
Methane, Nitrous Oxide
The “Greenhouse Effect”
The Earth’s surface thus receives energy from two sources: the sun & the atmosphere As a result the Earth’s surface is ~33C warmer than
it would be without an atmosphere
Greenhouse gases are transparent to shortwave but absorb long wave radiation Thus the atmosphere stores energy
Greenhouse Effect
Warms Earth Needed for life to
thrive Gases:
water vapor carbon dioxide methane, and nitrous oxide
Recent changes in greenhouse gas concentrations
What factors contribute to enhanced greenhouse effect?
What studies are being done? Are human activities causing Earth to warm?
Antarctica from space
Antarctica
Antarctica is covered by ice
How snow is squeezed into ice
How an ice sheet is made
Antarctic ice
How thick is this ice sheet?
Layered ice
The ice core drill rig
The ice core
Layers in ice cores
Handling ice cores
Studying ice cores
Ice core sites in Antarctica
Vostok
Selected Greenhouse Gases
Carbon Dioxide (CO2) Source: Fossil fuel burning, deforestation increase: 30%
Methane (CH4) Source: Rice cultivation, cattle & sheep ranching, decay
from landfills, mining increase: 145%
Nitrous oxide (N2O) Source: Industry and agriculture (fertilizers) increase: 15%
So, which human activities may be major causes of increasing global temperatures? The burning of fossil fuels Deforestation (taking out forests) Why? Increase of Carbon Dioxide in the
atmosphere because it absorbs long wave radiation (heat), thus preventing the heat from escaping.
Summary
Greenhouse gases absorb infrared radiation and prevent it from escaping to space.
Carbon dioxide, methane, and nitrous oxide are very goodat capturing energy at wavelengths that other compoundsmiss
Greenhouse Effect & Global Warming
The “greenhouse effect” & global warming are not the same thing. Global warming refers to a rise in the
temperature of the surface of the earth
An increase in the concentration of
greenhouse gases leads to an increase in the the magnitude of the greenhouse effect. (Called enhanced greenhouse effect) This results in global warming
Climate Change vs. Variability Climate variability is natural.
Even in a stable climate regime, there will always be some variation (wet/dry years, warm/cold years)
A year with completely “average” or “normal” climate conditions is rare.
The challenge for scientists is to determine whether any increase/decrease in precipitation, temperature, frequency of storms, sea level, etc. is due to climate variability or climate change.
Effects of Ozone Depletion
The Discovery
Team who discovered the hole 1985. From left: Joe Farman, Brian Gardiner, and Jonathan Shanklin
British Atlantic Survey Research station, Holly Bay, Antarctic coast
In 1985, using satellites, balloons, and surface stations, a team of researchers had discovered a balding patch of ozone in the upper stratosphere, the size of the United States, over Antarctica.
Earth’s Atmosphere
The ozone layer• Ozone is a triatomic form of
oxygen (O3) found in Earth’s upper and lower atmosphere.
• Ozone protects living organisms by absorbing harmful ultraviolet radiation (UVB) from the sun.
• The ozone layer is being destroyed by CFCs and other substances.
• Ozone depletion progressing globally except in the tropical zone.
www.epcc.pref.osaka.jp/apec/ eng/earth/ozone_layer_depletion/susumu.html
Chemical Mechanism
Different chemicals are responsible for the destruction of the ozone layer
Topping the list : chlorofluorocarbons (CFC’s) (chemicals from aerosol cans) man-made, non-toxic and inert in the troposphere, but in the
stratosphere they break apart and release reactive chlorine atoms that destroy the ozone layer.
A combination of low temperatures and elevated chlorine and bromine concentrations are responsible for the destruction of ozone in the upper stratosphere thus forming a “hole”. (Kerr, 1987)
www.met.sjsu.edu/~cordero/ education/education.htm
Ozone levels over North America (USEPA, March 1994)
• Comparing the colors of the bands over a particular city, such as Seattle, shows lower ozone levels in 1994 than in 1979
• Over the U.S., stratospheric ozone levels are about 5 percent below normal in the summer and 10 percent below normal in the winter
(U.S.E.P.A. 1994)
www.epa.gov/air/airtrends/ aqtrnd95/stratoz.html
No DataNo Data
Too much ultra-violet light can result in: Skin cancer Eye damage such as cataracts Immune system damage Reduction in phytoplankton (found in the ocean) Damage to the DNA in various life-forms
this has been as observed in Antarctic ice-fish that lack pigments to shield them from the ultra-violet light (they've never needed them before)
Possibly other things too that we don't know about at the moment
Effects on Human Health Over exposure may:
Increase risk of non-melanoma and malignant melanoma skin cancer
Higher risks of malignant melanoma from severe sunburns – especially in childhood
Risk of malignant melanoma has increased 10%
Risk of nonmalignant melanoma has increased 26%
malignant
Non-malignant
www.ldeo.columbia.edu/.../ lectures/ozone_health/
Over Exposure Suppress immune system Accelerate aging of skin due high exposure Cause an outbreak of rash in fair skinned people
due to photo allergy – can be severe
dermis.multimedica.de/.../ en/13007/image.htm
Skin Protection Protect the skin against the solar radiation
using skin creams with SPF The greater the numerical value of the SPF the
greater the protection Use lip balm with SPF Cover up
www.ldeo.columbia.edu/.../ lectures/ozone_health
cornea is encountered first
then the lens
vitreous humor
Increases the risk of cataracts Induces type of protein
that provokes cleaving (splitting) in the lens
Leading cause of blindness
The prevalence of cataract after age 30 is doubling each decade
Causes pterygium A wedge-shaped
growth over the central cornea
Over Exposure to UV-B….
Manifestations of…
Cataracts
Pterygium
Cancer
brought on by over exposure to UV-B
Protection Sunglasses with 100% UV block Wrap around sunglasses Eye protection for children Hats
Signs of Recovery???There have been some signs of recovery
1997 satellite showed a decline of several known ozone-depleting gases
Satellite images show some slowing down of ozone loss
However….
www.coolantarctica.com/. ../ozone_hole.htm
Recovery is slowAntarctica - Dec. 2005
Images of Antarctica Taken Indicate A Slow Recovery
Understanding the future
Researchers would like to see:
Stations that measure levels of ozone and surface radiation changes in relation to incidence rate of skin cancer and cataracts - installed in urban areas and in remote regions far from populations
More studies to determine biological effects (including human) on UVR exposure
Research on protective creams and ointments and their efficiency in preventing skin cancer and malignant melanoma
More surveillance of UV-related damage to other species living in high latitudes for example…..
Summing It All Up The Ozone is Earth’s only defense against harmful UVR Studies indicate ozone thinning throughout the globe due to 2
mechanisms: Meteorological Chemical
Research indicates microorganisms, are extremely sensitive to increasing UV-B levels
There is a lot of uncertainty and debate among researchers as to the degree in which land plants are affected by UV-B
There is debate in the scientific community in the role UV-B radiation plays on the decline of amphibians seen globally
In the last decade, there has been an increase in skin cancer and cataracts all related to increase UV-B exposure
Efforts Need to Be Continued Create reliable models
To gain a better understanding of the effects ozone depletion has on organisms living within different ecosystems
Enforcement of Montreal Protocol To reduce concentrations of chemicals responsible for
ozone depletion Monitoring chemicals being emitted
Gain a better overall understanding on just how ozone depletion is affecting our planet
...