Welcome to GLG101C Introduction to Geology Fall 2004 Professor James Tyburczy
Department of Geological Sciences
	Chapter 23 Earth's Environment, Global Change, and Human Impacts

Chapter 23 Earth's Environment, Global Change, and Human Impacts

Earth's linked 'spheres' - Inner Core, Outer Core, Deep Mantle, Asthenosphere, Lithosphere, Hydrosphere, Atmosphere

Biosphere - life lives in Lithosphere, Hydrosphere, Atmosphere -

• Earth’s geological environment and biological environment are linked

Components of the Climate System - (Climate = weather over long time scales)

• Atmosphere- Earth's atmosphere today - 78% N2, 21% O2, 1% Ar, 0.035% CO2, 0 to 3% H2O (depends on relative humidity). Tiny amount of O3 (ozone) - stratospheric shield.
• Hydrosphere - 96% of water in oceans, 3% glaciers and ice caps (called the 'cryosphere'), 1% groundwater and surface fresh water ('continental water'). Continental water is a crucial reservoir for moisture, also supplies the oceans with salt (ions dissolved in weathering process)
• Lithosphere - The land surface affects climate. It reflects solar energy (albedo) - depends on land cover. Topography affects climate - as in rain shadows. Arrangement of continents (plate tectonics) - affects ocean and wind circulation patterns - which affect climate. Volcanic eruptions link surface processes with internal processes. Aerosols and particulates from volcanic eruptions block solar radiation - can cool the earth for periods of years after a large eruption (e.g. Mt Pinatubo in 1992). Most of atmosphere originated from volcanic gases.
• Biosphere - Land vegetation is linked to surface moisture and temperature. Plants (through photosynthesis) regulate atmospheric CO2 and Oxygen (Green organisms use sunlight energy + CO2 + H2O to make organic matter + O2). Human activities - we are part of the Biosphere.

Greenhouse Effect

• Sunlight (visible wavelengths) passes through the atmosphere, warms the surface of the earth. The solid earth re-radiates that energy in infrared (heat) wavelengths. Greenhouse gases (CO2 and H2O) absorb that energy (instead of passing through as visible light does), and scatter it in all directions. So, instead of leaving the earth, the energy warms the lower atmosphere and the surface. It also evens out temperatures around the globe.

Natural Climate Variability

• Last 400,00 years - about 12 deg C variation in global average T, that matches perfectly with estimates of CO2 and methane (CH4) in that atmosphere (from measurements made on gases trapped is ice cores)
• Major part of the T variations is due to variations in Earth's orbital parameters (eccentricity, tilt, precession) that influence how sunlight reaches the Earth, but a significant part is due to fluctuations in greenhouse gases
• Last major glacial maximum- 25,000-18,000 years ago. Warming since about 14,000 years ago. We are currently (last 10,00 years, in a long-lasting warm period.)

Regional Variation

• El Nino (El Nino - Southern Oscillation; ENSO)- enhanced Pacific equatorial ocean flows - warm water flows from west to east. This causes drought in the tropics, rain and flooding in the east Pacific (South America) and wet winters in western US. Last major episode 1997-8. We are currently entering a mild El Nino condition.
• La Nina - opposite - cold water flows

Geochemical cycles - reservoirs, fluxes, residence time. Follow chemical elements through the Earth

The Carbon cycle.

• Reservoirs = atmosphere, biosphere, hydrosphere, solid earth (lithosphere)
• Gas exchange between ocean and atmosphere - moderates effects of fuel burning
• Photosynthesis - takes CO2 out of atmos, burning of fossil fuels releases CO2 to atmos
• Weathering of rocks - takes CO2 out of atmosphere and puts it in oceans.
• Sedimentation of carbonates on ocean floor - releases CO2 back to atmosphere plus CO2 into solid earth
• Volcanoes, metamorphism - puts CO2 into the atmosphere
• Man burning fossil fuels - upsetting the balance

Human Activity and Global Change - Click here for web info on global warming and more info on global warming.

Global warming and Greenhouse Gases - released by man’s activities

• Carbon dioxide (CO2) - released by burning fossil fuels and by deforestation (especially in the tropics) - CO2 is a greenhouse gas that has increased due to man's activities (isotopic evidence tells us this)
• Earth’s T has risen about 0.5 - 1 degrees C in last 100 years, coincides with increase in CO2 level of the atmosphere. Is increased CO2 the cause of the warming? Yes, because
  • Over the last 1000 years, average global trend is a cooling trend
  • During the last thousands of years, average fluctuations have been about 0.3 deg per 100 years - this last century has been a much larger change
  • Global atmospheric models are consistent with these results
• Estimated T increase in the next 100 years is 1 to 3 1/2 degrees C due to CO2 into atmosphere from man's activities
• Effects of increased global temperatures
  • Change in local climates (effects on agriculture)
  • Melt ice caps
  • Raise sea level
  • How long for oceans to absorb the excess? Estimate is hundreds of years
• Remedies - reduce use of fossil fuels (alternate energy sources, conservation, and efficiency), reduce tropical logging
• Kyoto Protocol 1997
  • An attempt to make a global plan to reduce CO2 emissions
  • Not yet ratified - Developed versus developing nations.

   

Chloro-fluoro carbons (CFCs) and Ozone depletion - Click here for web info on stratospheric ozone depletion

• Ozone (O3) near earth's surface is a pollutant (helps form smog)
• In the stratosphere (10 - 50 km up) ozone protects us from the sun's harmful ultraviolet radiation (UV)
• CFCs were commonly used as refrigerants, propellants, solvents until it was realized that when released into the atmosphere, they would migrate upward and destroy the ozone in the stratosphere (creating the 'Ozone hole' over the poles).
• 1989 Montreal protocols - phase out CFCs. Working pretty well.

Acid rain - SO2 (from fossil fuels, especially coal) plus H2O = sulfuric acid. Click here for web info on acid rain

• Downwind from industrialized areas - Northeast U.S., eastern Europe
• Sometimes local geology can mitigate - carbonate rocks can neutralize acid
• In last few years, reduction of acid rain in the eastern U.S., but increases in the west - coal fired power plants
• Remedies - flue gas desulfurization (expensive), conserve electricity

Geological and Environmental Issues and the Future - Click here for web info on global population

• Increased population growth is the greatest challenge to the environment
• Developing nations will continue to grow rapidly - will consume more resources, create more wastes
• Need for sustainable development
• Science and the citizen - Environmental issues (and their geological basis) will continue to be problems for the US and the world