2. Introduction
• Is the world getting warmer?
• If so, are the actions of mankind to
blame for earth’s temperature
increases?
• What can/should be done about these
issues?
3. History of Earth’s Climate
• Earth formed ~4.6 billion years ago
• Originally very hot
• Sun’s energy output only 70% of
present
• Liquid water present ~4.3 billion years
4. History of Earth’s Climate
• Life appeared ~3.8 billion years ago
• Photosynthesis began 3.5-2.5 billion years
ago
– Produced oxygen and removed carbon
dioxide and methane (greenhouse gases)
– Earth went through periods of cooling
(“Snowball Earth”) and warming
• Earth began cycles of glacial and
interglacial periods ~3 million years ago
In examining global warming, we will be looking at questions such as
Is the world getting warmer?
If so, are the actions of mankind to blame for earth’s temperature increases?
What can or should be done about global warming?
Are the potential resolutions to global warming worth the cost to implement them?
This is a big picture examination of the earth’s climate
The Earth was formed around 4.6 billion years ago
And was originally very hot
However, the Sun’s energy output was only 70% of what it is presently
Liquid water was present on the surface around 4.3 billion years ago
The first life forms appeared ~3.8 billion years ago
Photosynthesis began 3.5-2.5 billion years ago,
which produced oxygen and removed carbon dioxide and methane, which are greenhouse gases, from the atmosphere
As a result, the Earth went through periods of cooling, commonly referred to as “Snowball Earth” and subsequent warming
Earth began its current cycles of glacial and interglacial periods around 3 million years ago
The temperature of the earth is directly related to the energy input from the Sun. Some of the Sun’s energy is reflected by clouds. Other is reflected by ice. The remainder is absorbed by the earth.
If amount of solar energy absorbed by the earth is equal to the amount radiated back into space, the earth remains at a constant temperature.
However, if the amount of solar energy is greater than the amount radiated, then the earth heats up.
If the amount of solar energy is less than the amount radiated, then the earth cools down.
To a certain degree, the earth acts like a greenhouse. Energy from the Sun penetrates the glass of a greenhouse and warms the air and objects within the greenhouse. The same glass slows the heat from escaping, resulting in much higher temperatures within the greenhouse than outside it.
Likewise, the earth’s atmospheric gases affect the ability of the earth to radiate the Sun’s energy back into space. Nitrogen and Oxygen make up 99% of the earth’s atmospheric gases and are non-greenhouse gases. Water, Carbon Dioxide, and Methane make up 1% of the earth’s atmosphere, but are greenhouse gases, since they cause the earth to retain heat.
