Download Global Warming overview (3)

Layers of the Atmosphere
1.
Troposphere
TROPOSPHERE
This is the layer of the atmosphere closest to the Earth's surface, extending up to about 10-15 km above the Earth's surface. It
contains 75% of the atmosphere's mass.
At the very top of the troposphere is the tropopause where the temperature reaches a (stable) minimum. Some scientists call the
tropopause a "thermal layer" or "cold trap" because this is a point where rising water vapour cannot go higher because it changes
into ice and is trapped. If there is no cold trap, Earth would loose all its water!
Most of what we call weather occurs in the troposphere. The uneven heating of the regions of the troposphere by the Sun causes
convection currents and winds. Warm air from Earth's surface rises and cold air above it rushes in to replace it. When warm air
reaches the tropopause, it cannot go higher as the air above it (in the stratosphere) is warmer and lighter ... preventing much air
convection beyond the tropopause. The tropopause acts like an invisible barrier and is the reason why most clouds form and
weather phenomena occur within the troposphere.
The Greenhouse Effect: Heat from the Sun warms the Earth's surface but most of it is radiated and sent back into space. Water
vapour and carbon dioxide in the troposphere trap some of this heat, preventing it from escaping thus keep the Earth warm. This
trapping of heat is called the "greenhouse effect".
However, if there is too much carbon dioxide in the troposphere then it will trap too much heat. Scientists are afraid that the
increasing amounts of carbon dioxide would raise the Earth's surface temperature, bringing significant changes to worldwide
weather patterns ... shifting in climatic zones and the melting of the polar ice caps, which could raise the level of the world's
oceans.
2.
STRATOSPHERE
This layer lies directly above the troposphere and is about 35 km deep. It extends from about 15 to 50 km above the Earth's
surface.
The stratosphere is warmer at the top than the bottom. The lower portion has a nearly constant temperature with height but in
the upper portion the temperature increases with altitude because of absorption of sunlight by ozone. This temperature increase
with altitude is the opposite of the situation in the troposphere.
The Ozone Layer: The stratosphere contains a thin layer of ozone molecules (with three oxygen atoms) which forms a protective
layer shielding life on Earth from the Sun’s harmful ultraviolet radiation. But this ozone layer is being depleted, and is getting
thinner over Europe, Asia, North American and Antarctica. "Holes" are appearing in the ozone layer.
3. MESOSPHERE
Directly above the stratosphere, extending from 50 to 80 km above the Earth's surface, the mesosphere is a cold layer where the
temperature generally decreases with increasing altitude. Here in the mesosphere, the atmosphere is very rarefied nevertheless
thick enough to slow down meteors hurtling into the atmosphere, where they burn up, leaving fiery trails in the night sky.
4. THERMOSPHERE
The thermosphere extends from 80 km above the Earth's surface to outer space. The temperature is hot and may be as high as
thousands of degrees as the few molecules that are present in the thermosphere receive extraordinary large amounts of energy
from the Sun.
Solar Budget – the balance between incoming energy (light) for m the sun and
outgoing energy from the sun (light and heat)
The Greenhouse Effect
The conversion of light into heat and the delayed release of this heat back to space warms our atmosphere….greenhouse effect.
The heat is store and delayed by greenhouses gases such as H2O, CO2, CH4, N2O, Fluorinated gases (CFC, HCFC), These gases are listed in terms of order of
magnitude of effect.
Humans are increasing the amount of greenhouses gases and therefore causing increased storage and greater delay of heat being released to space = global
warming (anthropogenic global warming).
Video links…
https://www.youtube.com/watch?v=Hi3ERes0h84
http://video.nationalgeographic.com/video/101-videos/global-warming-101
https://www.youtube.com/watch?v=ab6jV4VBWZE
Global Warming Sceptics…
https://www.youtube.com/watch?v=Wq_Bj-av3g0
https://www.youtube.com/watch?v=7sGKvDNdJNA
https://www.youtube.com/watch?v=zORv8wwiadQ
Intergovernmental Panel on Climate Change:
https://www.youtube.com/watch?v=rUY9iijwxDQ
Discussion questions….
How are humans increasing greenhouse gases?
Why is the term global warming increasingly replaced by global climate change?
What are the potential social, economic and environmental impact of global climate change?
Is climate change really anthropogenic?
Does it matter if it is or isn’t anthropogenic?