Earth Sciences 2240F/G Lecture Notes - Lecture 6: Ultraviolet, Meteoroid, Thermostat
11 Jun 2018
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Catastrophic Events Notes: Part 2
2.0 Energy from Sun
• Weather: the short term state of the atmosphere at a given time
and place, with respect to variables such as temperature, moisture,
wind velocity and barometric pressure
o i.e. thunderstorms, tornadoes, hurricanes
• Climate: the average long-term weather conditions for a region of
earth, including things like average temperature and precipitation
• Get energy form the sun, but processes on earth have influenced
weather and climate by interfering with sun’s energy
• Today, primary climate-changing influence is from human-related
processes
2.1 Earth’s Greenhouse
• strength of greenhouse controls warmth of bodies of water (heat for
cyclonic storms) and the atmosphere (thus climate)
• in-coming ultraviolet radiation passes through the atmosphere
much more readily than outgoing infrared radiation
• two gases currently increasing most rapidly and have the property
of reflecting infrared radiation back to earth are carbon dioxide
CO2 and CH4 (methane)
• Venus- sometimes called the ‘twin’ of earth- because of similarity
in size not much else
o Receives twice the solar radiation that earth gets
o Early days of development, both venus and earth had similar
greenhouse gases made of CO2 emissions coming from
volcanoes, and both had oceans of water
o GHGs of Venus strengthened to point that all water
evaporated, leaving a surface temperature of about 460 C
o Result is that all carbon of venus is stored as CO2 in its
atmosphere
o Earth vast majority of CO2 stored in rocks, fossil fuels and
plants with little in atmosphere
o Earth mostly habitable, whereas venus never habitable
o Difference explained by difference in solar radiation, but not
only, something is acting as a thermostat…
3.0 Energy from Impacts
• another external energy source: meteoroids, asteroids and comet
impacts
• earth receives 100-1000 tonnes of matter from space every day,
mostly dust
• 472 in city of Constantinople (present Istanbul), large meteoroid
enter atmosphere, rock pulverized on impact, impact site never
found, small ~ 10m in diameter
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