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 Layers

1) 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 Maximum Stratosphere 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, O

Oxide

3

Methane, Nitrous

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 ~33  C 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 (CO 2 )

 Source: Fossil fuel burning, deforestation  increase:

30% Methane (CH 4 )

 Source: Rice cultivation, cattle & sheep ranching, decay from landfills, mining 

Nitrous oxide (N 2 O)

 Source: Industry and agriculture (fertilizers)  increase: increase:

145% 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 good at capturing energy at wavelengths that other compounds miss

Greenhouse Effect & Global Warming

 The

“greenhouse effect” warming

&

global

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



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.

Team who discovered the hole 1985. From left: Joe Farman, Brian Gardiner, and Jonathan Shanklin British Atlantic Survey Research station, Holly Bay, Antarctic coast

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) No Data No Data www.epa.gov/air/airtrends / aqtrnd95/stratoz.html

• 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)

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%

www.ldeo.columbia.edu/.../ lectures/ozone_health/ Non-malignant malignant

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

Over Exposure to UV-B….

  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 vitreous humor then the lens cornea is encountered first

www.ldeo.columbia.edu/.../ lectures/ozone_health

Manifestations of…

Cancer Cataracts

brought on by over exposure to UV-B

Pterygium

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….

Antarctica - Dec. 2005

Recovery is slow

www.coolantarctica.com/. ../ozone_hole.htm

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 ...