ENVS 1100 Lecture Notes - Lecture 15: Shortwave Radiation, Longwave, Water Vapor
3 May 2018
School
Department
Course
Professor
Climate Change – Global Warming
November 20, 2014
Climate Change – Alteration in the long-term patterns and statistical averages of
meteorological events
Weather – Meteorological conditions in a given place on a given day
Climate – long-term patterns or trends of meteorological events
The Earth absorbs 70% and reflects 30% of incoming shortwave radiation from the
sun. Note that the Earth warms and emits long wave radiation. The Greenhouse
Effect is impacting the amount of radiation reflected. Some of the radiation is
trapped by greenhouse gases in the atmosphere and warms the planet.
Albedo – surfaces or materials that reflect the solar radiation from Earth
• For example, glaciers, melting snow and glass are albedos
If the landscape and surface area changes in regions due to climate change, it can
affect the amount of radiation reflected.
Greenhouse gases – molecules in the atmosphere that absorb heat and reradiate it
back at Earth
Greenhouse effect – the warming of the planet that results when heat is trapped by
Earth’s atmosphere
Greenhouse Gases
• Water vapor*
• Carbon dioxide*
• CFCs
• Methane
• Nitrous Oxide
• Tropospheric Ozone
UV Radiation: 0.1-0.4nm
Visible Light: 0.4-0.7nm
Infrared Radiation: 0.7-100nm
* = Main Greenhouse Gas
These Greenhouse gases have a higher absorptivity for infrared radiation (long
wave) that the Earth emits. This is why these gases trap the radiation and cause the
Earth to warm.
Radiative Forcer – anything that alters the balance of incoming solar radiation
relative to the amount of heat that escapes out into space
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For the Earth’s system to be at equilibrium, it must be emitting as much energy as it
is absorbing.
If there was no greenhouse effect the temperature would be around -15°C. This
temperature would be inefficient for many human activity and other plant/animals.
Energy In=Energy Out
At the top of the atmosphere, the energy coming in from the sun is balanced by the
sunlight reflected back to pace and the net infrared emission from the Earth is
constant:
Sunlight In= Sunlight reflected from clouds/atmosphere + sunlight reflected
from surface + Infrared Emission
Positive Feedback Loop – changes caused by an initial event that then accentuate
that original event
• When sea ice melts, it uncovers water (darker surface with lower albedo)
• This activates a positive feedback loop as the exposed water absorbs sunlight
and releases more heat into the atmosphere
• This causes more ice to melt and more water to become exposed
• NOTE: During the last century, glaciers in many places have been shrinking
Negative Feedback Loop – changes caused by an initial event that trigger events
that then reverse the response
Results of Rising Sea Level:
• As glaciers and ice melt, increased water will flow into oceans
• As oceans warm, they expand (thermal expansion)
• Has large impacts on populations living near the coast
• Island nations under threat
The rate of sea level rise since the mid-19th century has been larger than the mean rate
during the previous two millennia.
A shift in only a few degrees in the average global temperature will likely result in
more and frequent extreme heat waves.
Evidence of Climate Change
1. Warmer Temperatures
2. Melting Ice
3. Sea level Rise
4. Weather Extremes
a. Precipitation changes
b. Increase in Storms
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The earth absorbs 70% and reflects 30% of incoming shortwave radiation from the sun. Note that the earth warms and emits long wave radiation. Effect is impacting the amount of radiation reflected. Some of the radiation is trapped by greenhouse gases in the atmosphere and warms the planet. Climate change alteration in the long-term patterns and statistical averages of. Weather meteorological conditions in a given place on a given day. Climate long-term patterns or trends of meteorological events. Albedo surfaces or materials that reflect the solar radiation from earth. Greenhouse gases molecules in the atmosphere that absorb heat and reradiate it. Greenhouse effect the warming of the planet that results when heat is trapped by. If the landscape and surface area changes in regions due to climate change, it can affect the amount of radiation reflected: for example, glaciers, melting snow and glass are albedos back at earth. Greenhouse gases: water vapor, carbon dioxide, cfcs, methane, nitrous oxide, tropospheric ozone.
