The Earth System. Earth: An overview 4 main spheres Hydrosphere (hydro=water) Biosphere (bio=life)...

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

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