Q1) 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 meter, but the energy leaving Earth’s surface averages 390 watts per square meter. Why isn’t Earth cooling rapidly?
When the earth was formed, the particles that accreted actually had some energy so when they got together that energy was imparted into the Earth and it had some embodied energy to start with.
Another reason is due to gravity. Because gravity works through an object’s centre of mass, heavier objects are pulled towards the centre of the Earth and lighter objects are therefore displaced above them towards the surface, and that would have generated some frictional effects. Therefore some gravitational potential energy was converted into heat. However, these two mechanisms are quite minor contributions. The biggest mechanism is what we call radiogenic heating.
The Earth is a giant nuclear reactor. There are particles in the Earth’s core and throughout the mantle which are radioactive. When things decay radioactively they produce heat. The vast majority of the Earth’s energy is coming from the radioactive decay of these components, and they include things like thorium and also potassium. Therefore the earth is not actually cooling down, as geological estimates are that the Earth loses heat at a rate of about 50 terawatts. That’s about 50,000 1 gigawatt power stations worth of heat loss, i.e. if power stations pump out power at a rate of 1 gigawatt then you’d need about 50,000 of them – that’s how fast the Earth is losing heat through the oceans, continental surfaces, volcanoes and so on, and that means that those processes inside the Earth must be producing heat energy at a similar rate to balance things out because the Earth isn’t cooling down that much.
Q2) Do you think the statement made by the cartoon is justified? Explain.
No. A warming climate might affect snowfall. There are two competing effects as the climate warms: the increasing temperature causes a changeover from snow to rain, but it also increases the amount of water vapor in the atmosphere. For a particular place and time of year, which effect wins out depends on the temperature to begin with.
For relatively mild regions, we would expect heavy snowfall to become increasingly rare as the climate warms. But in colder regions, heavy snowfalls can become more frequent because of increases in the amount of water vapor in the atmosphere or, in some cases, because of changes in the circulation of the atmosphere, such as a shift in position of the storm track.
Extremely heavy snowfall requires a combination of an intense storm and the right temperatures. If it’s too warm, then most of the precipitation falls as rain. If it’s too cold, then there isn’t enough water vapor to give a big snowfall. All else being equal, there is a sweet spot in a fairly narrow temperature range around 24 degrees Fahrenheit.
Q3) One of the first radar devices developed during World War II used microwave radiation of a specific range that triggers the rotation of water molecules.Why was the design not successful?
The design was not successful as there exist water molecules in the atmosphere which are able to absorb the radiation, interfering the detection of intended objects.
Q4) 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? In the long run?
In the short run, air quality has the most severe impact on mankind because of its direct impact on health. Poor air quality can cause respiratory problems in humans when inhaled and its health effects surface within a short time span.
Global warming and ozone depletion pose a more serious threat in the long run, however, because their impact on human lives are indirect. Global warming causes melting glaciers resulting in rising sea levels that may submerge low-lying lands and ozone depletion allows the penetration of harmful UV-C radiation through the stratosphere in the Antarctica region. Due to the absence of human population in the Antarctica, the effects of UV-C radiation does not directly impact mankind. Thus global warming and ozone depletion are less of a threat in the short run compared to air quality.
In the long run, global warming would pose a more serious threat as entire low-lying civilisations would be submerged. On the other hand, the effects of cancer due UV-C radiation only surfaces after prolonged exposure and would take an extended period of time for the severity of its effects to be apparent.