Atmospheric Changes Resulting From Human Activities

• Factors that contribute to global warming.• Possible climatic impacts of global warming.• Factors that contribute to loss of the ozone

shield.• Possible impacts of UV light penetration.• Atmospheric Pollution: Acid Rain

Atmospheric Structure

Jet Streams300 mph

Climate

• Defined as the average trend in temperature and rainfall that produces a unique assemblage of plants and animals.

• Climate is modulated by differential solar radiation, which established major atmospheric circulation patterns. The polar regions are areas of net heat loss.

• Atmospheric circulation and ocean circulation distribute solar energy input as heat from the tropics and temperate latitudes to the poles.

Oceanic Heat Transport

Oceanic Conveyor System

Thermohaline (temperature + salinity effect on water density)

Past Climates

Climate and ocean circulation has not always been as we see it today. General conditions of ocean and atmosphere have existed since the last major glaciation event about 12,000 – 10,000 years ago (Younger Dryas)

Global Surface Temperatures

Terawatt = 1012 W

Atmospheric CO2 Concentrations

CO2 Emissions From Fossil Fuel Burning

• 35% higher than before industrial revolution

• 24 billion tons CO2 added each year

• Deforestation adds another 1.6 billion tons

• Where does it all go in addition to the atmosphere?– Oceans = CO2 sink

– Forests = CO2 source

Ocean and forests reduce the potential rate in carbon dioxide rise from 3 ppm/y to 1.7 ppm/y

Other Greenhouse Gases and Sources

• Water vapor• Methane• Nitrous oxide• CFC’s and other

halocarbons

• Hydrological cycle• Animal husbandry• Chemical fertilizers*• Refrigerants*

* = Long residence times and contribute toozone depletion

Evidences of Global Warming

• Nine out of 14 hottest years

• Wide-scale recession of glaciers

• Sea level rising

Predicted mean global temperature changeby 2100 is between 1.5 and 4.5 Co

Impacts of Global Warming

• Melting of polar ice caps• Flooding of coastal areas• Massive migrations of people inland• Alteration of rainfall patterns• Deserts becoming farmland and farmland

becoming deserts• Significant losses in crop yields

The El Nino: What Happened?

• Development of warm water in the eastern pacific over time.

• Reversal in trade winds that normally blow from an easterly direction.

• Warm water spread to the east.• Global patterns in moisture and

evaporation changed.

The El Nino: What Happened?

• Jet streams shifted from normal course.

April May

June September

The El Nino Effects

Reducing CO2 Emissions (True or False)

• Reducing use of fossil fuels• Adopt a wait-and-see attitude• Develop alternative energy sources• Plant trees• Examine other possible causes of global

warming• Make and enforce energy conservation rules• Rely on the government• Adopt the precautionary principle• Raise the minimum driving age to 18 years

Framework Convention on Climate Change (FCCC; 1997)

• “Kyoto Accord”• Reduce emissions to 1990 levels by 2010• For US to achieve this requires a 30% reduction of

present use. (Republican congress voted NO.)

• Globally, by 2010 CO2 emissions will have increased by 30% due to developing countries.

• Bottom line: need 60% reduction in CO2 emission worldwide NOW to stabilize greenhouse gas concentrations at today’s levels.

Ozone

Good Ozone!

Bad Ozone!

Electromagnetic Spectrum

Affects of UV Light Exposure

• Skin cancer (700,000 new cases each year)

• Premature skin aging• Eye damage• Cataracts• Blindness

Formation of the Ozone Shield

Reaction #1: UV light + O2 O + O

Reaction #2: Free O + O2 O3

Reaction #3: Free O + O3 O2 + O2

Reaction #4: UV light + O3O + O2

Chlorofluorocarbons (CFC’s)

• Organic molecules in which both chlorine and fluorine atoms replace some of the hydrogen atoms.

• Sources:– refrigerators and air conditioners– production of plastic foam– cleaner for electronic parts– pressurizing agent in aerosol cans

Breakdown of Ozone Shield

Reaction #5: CFCl3 + UV Cl + CFCl2

Reaction #6: Cl + O3 ClO + O2

Reaction #7: ClO + ClO 2Cl + O2

Which reaction releases Cl from CFC’s?

Which reaction generates more Cl?Chlorine is a catalyst that destroys the production of ________?

Montreal Protocol

• 1987 - scale back CFC production by 50% by 2000

• 1990 - amendment to completely phase out ozone destroying chemicals by 2000

• 1992 - amendment to completely phase out ozone destroying chemicals by 1996

Why the rush?

The Clean Air Act: Title IV

• Restricts production, use, emissions and disposal of ozone depleting chemicals.

• Regulates the servicing of refrigeration and air-conditioning units.

“Protecting Stratospheric Ozone”