Background
The background knowledge presented in this unit contains information well beyond the scope of what the students are expected to learn. This is because much of the things that students will learn will (hopefully) lead to questions which could go in many directions. This unit is relatively narrow, but as an educator you need to be prepared to answer questions that could be all over the place. I will keep what is known for fact and what is assumptions based on trends and data separate, but be aware that there are some conclusions in this unit that the scientific community is only 99% sure of, we do not know them for fact. Another note: there is propaganda that there is much "error" in the experiments and models used to predict the consequences of global warming. Remember that in scientific terminology "error" is more precisely defined as uncertainty. Also, even where there is uncertainty, there is much that we are certain about. We do not know the exact length of a ruler, there is error/uncertainty in even those measurements (matter is constantly moving so its exact length is constantly changing). Saying that the temperature will increase 3?C with an error of +/- 2?C still means that there will be an increase in temperature; and given that range of temperature the seas will raise between 3m and 25m, while yes, we are not sure how much, we do know it will rise and many of the conditions that will cause the 3m versus the 25m rise.
What is Global Warming
So how does global warming occur? Basically, when the rays from the Sun hit the Earth, a lot are instantly reflected, but some are temporarily absorbed then re-emitted. Those re-emitted rays are altered while absorbed (their frequency changes), so when they hit the atmosphere in their way out they are (in large part) absorbed by the atmosphere, then re-emitted, roughly half of it going back towards the Earth. They keep bouncing between the surface of the Earth and the atmosphere until they finally can escape. All the time they are bouncing back and forth, while not warming the planet after that initial bounce, they are keeping the energy in the system higher. The Earth warms when the trapped energy plus the incoming energy from the Sun is greater than the current temperature and the energy released into space. More gases released (like CO 2 and Methane) mean more energy is trapped, leading to an increase in temperature.
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