to GLG101C Introduction to Geology
Professor James Tyburczy
of Geological Sciences
23 Earth's Environment, Global Change, and Human Impacts
Earth's Environment, Global Change, and Human Impacts
linked 'spheres' - Inner Core, Outer Core, Deep Mantle, Asthenosphere, Lithosphere,
- life lives in Lithosphere, Hydrosphere, Atmosphere -
geological environment and biological environment are linked
of the Climate System - (Climate = weather over long time scales)
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
- 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)
- 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.
- 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.
(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.
- 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)
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
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.)
- 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
cycles - reservoirs, fluxes, residence time. Follow chemical elements through
The Carbon cycle.
= atmosphere, biosphere, hydrosphere, solid earth (lithosphere)
- Gas exchange
between ocean and atmosphere - moderates effects of fuel burning
- takes CO2 out of atmos, burning of fossil fuels releases CO2 to atmos
of rocks - takes CO2 out of atmosphere and puts
it in oceans.
of carbonates on ocean floor - releases CO2 back to atmosphere plus CO2 into
metamorphism - puts CO2 into the atmosphere
- Man burning
fossil fuels - upsetting the balance
Activity and Global Change - Click here for web
info on global warming and more
info on global warming.
warming and Greenhouse Gases - released by mans 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)
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?
the last 1000 years, average global trend is a cooling trend
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
atmospheric models are consistent with these results
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
in local climates (effects on agriculture)
- How long
for oceans to absorb the excess? Estimate is hundreds of years
- reduce use of fossil fuels (alternate energy sources, conservation, and
efficiency), reduce tropical logging
- Kyoto Protocol
- An attempt
to make a global plan to reduce CO2 emissions
- Not yet
ratified - Developed versus developing nations.
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
- 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.
rain - SO2 (from fossil fuels, especially coal) plus H2O = sulfuric acid. Click
here for web info on acid rain
from industrialized areas - Northeast U.S., eastern Europe
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
- flue gas desulfurization (expensive), conserve electricity
and Environmental Issues and the Future - Click here for web
info on global population