This is part 2 of the “Global Warming effects article” …continued here:

Greenhouse gases and CO2
The Sun’s rays hit the earth as long-wave radiation, which passes through greenhouse gases easily. However when they hit the earth the warm the planet and the energy is then radiated out from Earth as short wave infra-red radiation (heat) which is easily absorbed by greenhouses gases before it escapes into space. So the world gets warmer. This is the greenhouse effect and the leading greenhouse gases impacting on the environment are water vapor, CO2, methane, nitrous oxide, and ozone.

Global industrialization has driven the increase of greenhouse gases in the atmosphere through two mechanisms. Firstly the need for energy and chemicals has driven us to exploit fossil fuels (coal, oil and natural gas) so releasing carbon that has been trapped, inertly, underground in the form of oil, coal or natural gases, back into the atmosphere as carbon dioxide.

Secondly the need for more farmland, to feed the increased population, has driven the destruction of a large percentage of the World’s rainforest. This is a double whammy since not only does cutting down and burning forest release methane and carbon dioxide, but it also destroys that forest’s ability to remove CO2 from the atmosphere by photosynthesis. Agriculture has also driven the use of nitrogen fertilizers which contribute to the formation of nitrous oxide.

Aerosols and pollution
The other impact of industrialization and deforestation is the emission of small particles of pollutants into the atmosphere (smoke or soot) from factories, power stations, and forests cleared using fire. (Volcanic eruptions also emit large quantities of sooty pollutants into the air, causing a similar effect naturally). Strangely the presence of these particles in the atmosphere actually helps to cool the World by keeping out the sun’s rays (see the next section on albedo).

As a result of the obvious human harm done by air-based pollutants, Governments started implementing effective measures to reduce air pollution (for example the UK’s Clean Air Act of 1956, and the USA’s Air Pollution Control Act of 1955). However, ironically, the cooling effect of air pollution could actually have been moderating the warming effect of greenhouse gases, meaning that by solving one pollution problem we may have exacerbated another.

Albedo (or the reflectivity of the planet)
Finally, the Earth’s albedo (the degree to which it reflects or absorbs radiated energy) has been modified by both people directly and by trends in global temperatures. Firstly cutting down dark forests, to make way for lighter colored meadows and crop fields, reflects more of the sun’s energy back into space (slowing global warming). However the melting of highly reflective ice caps reduces the reflectivity of the earth driving warming.

Cloud cover also increases the Earth’s albedo, reflecting the sun’s radiation back into space. Contrarily more cloud also increases the greenhouse effect by trapping the heat emitted by the Earth. The precise balance of these two effects is still open to uncertainty, as is the general trend of cloud cover at different heights (is cloud cover increasing or decreasing and will a warmer planet be a cloudier one?).

Solar radiation
This leaves just the impact of solar radiation. This is a controversial one since a small minority of scientists has argued that short-term solar cycles are solely responsible for recent global warming, and that greenhouse gases are in no way responsible. Although we shouldn’t dismiss solar cycles entirely it is probably stretching things to say they bear all the blame.

The way forward
So what remains to be done about this problem? Generally speaking there are two schools of thought (if we exclude the option of denying it completely). Firstly we can try to live with the consequences, without modifying our behavior at all. And the second is that we try to reduce global warming by reducing greenhouse gas emissions and deforestation among other things.

This is where the real controversy lies. For example if we choose to ignore global warming we might contribute to sea level rises that flood low level areas of land (such as Island nations or Bangladesh, or to desertification in equatorial regions. But we might also see the expansion of habitable zones in polar regions. To what extent are the nations that benefit from that decision responsible to those that lose out?

On the other hand if we impose large costs on industry to limit greenhouse gas emissions we may also limit the economic development of poorer nations such as India and China. Increasing the health and wealth of developing nations almost inevitably requires increases in energy consumption and therefore CO2 emissions. The same economic growth that is driving up CO2 levels in the atmosphere has reduced the number of people in the world living in poverty by a little over half a billion (or has halved the global levels of poverty, measured in comparative terms) since 1981.

My hunch is that all sides in the debate are going to have to accept difficult decisions (such as using more nuclear energy and banning grown bio-fuels outright). We will probably have to get a move on in developing viable renewable energy such as solar power and wind energy. The truth we is that we will probably also have to live with a certain amount of human caused environmental change.