1. Understanding Earth’s energy balance is essential to understanding the issue of global warming. For example, the solar energy striking Earth’s surface averages 168 watts per square metre (W/m²), but the energy leaving Earth’s surface averages 390 (W/m²). Why isn’t Earth cooling rapidly?

• The emitted heat energy is mainly retained by the atmosphere thus the Earth does not cool rapidly even though the energy leaving Earth’s surface is almost twice of the energy that strike Earth’s surface.

2. Decide and explain where the stamen is correct or incorrect. Explain.

• The stamen is incorrect. The difference between weather and climate is the measure of time. Climate describe the average weather for a certain region in the long term of decades of year while weather describes the condition of the atmosphere over a short period of time. Having said that, particularly cold seasons like the winter will not mean that the Earth is getting cooler. Thus, using weather as a reference is not reliable. It would be more reliable to use climate for statistical data about the Earth’s temperature and warming/cooling trends.

3. One of the first radar devices developed during World War II used microwave radiation of a                        specific wave range that triggers the rotation of water molecules. Why was the design not                            successful?

• Water in the atmosphere absorb the microwave radiation and this will interfere with the detection of the subject thus it was not successful.

4. Now that you have studied air quality (Unit 1), stratospheric ozone depletion (Unit 2), and                          global warming (Unit 3), which do you believe poses the most serious problem for you in the                      short run (pick one and explain)? In the long run (pick one and explain why)?

•  [Short Run] I believe that air quality will pose the most serious problem for us in the short run. This is because we live in Singapore, a bustling city where transportation and industries are booming. This causes a lot of emission and affects the air quality.

• [Long Run] The stratospheric ozone depletion will pose the most serious problem for us in the long run. It does not pose a direct and immediate effect because of the proximity of the ozone hole from Singapore. Over exposure to ultraviolet (UV) light can damage the skin or cause sunburn. In some cases, it leads to an increased risk of certain kind of skin cancer.