EGEE 102
Energy Conservation and Environmental Protection

Global Warming


The sun is the main source of energy and, as we discussed earlier, it is the net balance between the incoming solar energy and the outgoing energy that causes the temperature changes.

The Earth is continuously moving around the sun. Based on its position, the incoming energy changes. The Earth’s axis of rotation is tilted at an angle of 23.5°, and this tilt goes from one side to the other and back over in 40,000-year cycles. Earth’s axis of rotation takes about 21,000 years to complete a cycle.

Instructions: Click the play button below to view the earth’s movement around the sun.

Earth's movement around the Sun

The Earth’s orbit around the sun changes from a circular path to an elliptical path and back to a circular path over 100,000 years. These are long-term changes. On a much shorter term, the radiation from the sun can be affected by the activity on the surface of the sun. Sun spots (intense flares on the surface) can increase the radiation from the sun. The increase in the solar activity occurs over an 11-year cycle.

Like many fields of scientific study, there are uncertainties associated with the science of global warming. This does not imply that all things are equally uncertain. Some aspects of the science are based on well-known physical laws and documented trends, while other aspects range from 'near certainty' to 'big unknowns.'

On the following pages, we will discuss the following:

  • What is known for certain? Human activities change the Earth's Atmosphere.
  • What is likely? Greenhouse gases contribute to global warming. Several factors impact temperature (clouds, fine particles, oceans). Global Warming affects health, water resources, polar regions, coastal zones and forests.
  • What is uncertain? The long term effects of global warming, especially for smaller areas.
What is known about global warming activity