9-1a Reading - Global Warming

The Causes of Global Warming

The Earth’s climate has changed throughout its history, and life on the this planet has continually adapted to whatever changes mother nature has thrown at it. Some animals die when weather patterns change while others thrive and find new opportunities because it is either warmer or colder. Human beings, unlike any other species, have an awareness of how the climate changes over long periods of time because of their ability to record weather patterns and predict future trends. In the late 20th and 21st centuries, there has been concern that not only is the planet experiencing a cycle of warming, but that human beings are actively contributing and even speeding the process of global warming. Some statistics about what results these changes could have on people’s lives are quite shocking, so discussion continues about global warming and, in particular, what is causing it. There are natural forces, such as the Sun itself, that need to be outlined, but it is the man-made factors of the burning of fossil fuels and unchecked deforestation that have captured most of the media’s attention.

Some but not all planets like Earth have a molten core of super-heated rock and minerals that makes its way up to the surface, so it could appear that this is the primary source of heat for the planet, yet it is in fact the Sun and the energy it sends 150 million kilometers through space. The Sun, like other stars, is a giant ball of gas which is undergoing constant nuclear explosions far greater than any ever created on Earth, and this process, known as fusion, sees hydrogen converted into helium. The result is tremendous amounts of light and energy which is thrown away in all direction, including towards Earth. This energy, particles of light called photons, reaches the Earth and passes through its atmosphere. Some of the energy is absorbed by the atmosphere, which is a good thing as the raw force of the Sun’s radiation would kill all life otherwise. The energy that does get through heats the air on its way down, hits the ground and heats the surface, then bounces back up into the Earth’s atmosphere and back out into space (Figure 1.). There is a balance between how much radiation is absorbed as it enters the atmosphere and how much is allowed to leave that allows life to continue on the planet. If certain gasses in the atmosphere are too thick, too much heat would remain inside and not return to space. The reverse is also true if the atmosphere is too thin as heat would dissipate far too quickly and the temperature would drop drastically. This is the essential description of the “greenhouse effect” that equates the Earth and its atmosphere to a glass greenhouse which traps heat inside in a similar way.

The relationship between the Sun and the Earth’s temperature appears fairly straight forward; however, the Sun is not a constant supplier of energy and the amount it emits can vary greatly. The Sun has hot and cold spots which can be observed from Earth and these have been recorded by astronomers over hundreds of years. With this data, there is proof that the climate on the Earth and the Earth’s temperature is directly affected by the cycles of heating and cooling in the Sun. One historical event that is pointed to is that from around the year 1650 until 1850, most of Europe experienced a substantial drop in temperature that saw glacial ice fields expand, rivers freeze over that never had before, and growing seasons shorten considerably. It came to be known as the “Little Ice Age”, though it was not a true ice age in that sense. During this same time, it was observed that the Sun experienced far less sun spots, darker areas that indicate cooling yet greater amount of energy output, and there seems to be a direct correlation between the solar activity of the time and Earth’s climate, making the Sun a major factor in any global warming debate (NASA, n.d.). Some question this and point to other periods of solar cooling during which the Earth actually warmed. Readings of global temperature from 2004 to 2007 indicated a rise in temperature and a drop in solar activity, yet NASA showed that, although the Sun was actually emitting less overall radiation at that time, it sent far more visible light and radiation near infra-red wavelengths (Page, 2010). These are shorter wavelengths of light that can penetrate the atmosphere much more easily, resulting in the warming trend. The temperature of the Sun is not, then, as relevant as the amount and type of energy it’s sending to the Earth, making the Sun a huge factor in global warming.

People have no control over the Sun and the energy it sends to Earth and the best they can do is to adapt to the situation it creates, but there are human activities which are believed to make global warming trends even worse by changing the composition and balances of gasses in the atmosphere, of which the most talked about is the burning of fossil fuels. Fossil fuels, primarily oil, coal, and natural gas, by themselves do not cause global warming because in their natural state and location, they do not normally interact with the environment at all. These forms of potential energy are usually sitting underground, sometimes extremely far, and it is only when humans find uses for them that they are a concern. The key ingredient in fossil fuels is carbon, which, in the form of carbon dioxide (CO2), is a powerful greenhouse gas. Although the atmosphere is comprised of only 0.04% CO2, it plays an essential role in absorbing heat from outgoing solar radiation and when its proportion rises even slightly, the effects are felt (Fischer, 2011). Fossil fuels are made from organic material in one way or another, and organic material is made up of a great deal of carbon. The argument is that these fuels are acting as storage of excess carbon that the planet may not easily be able to reabsorb.

The fossil fuels which contain carbon are relatively inert until they are broken down through the process of burning, which is where human activity comes into play. Before the mid-18th century and the advent of the Industrial Revolution, fuels were burned mainly for light and cooking purposes and there weren’t the large engines and furnaces that need a constant source of energy. With the advent of steam engines and industrialized processes, the demand for items like coal increased significantly and there seems to be a direct correlation between the increase of fossil fuel consumption and the increase in levels of CO2 in the atmosphere (Figure 2.). Today, they are used to power nearly everything people do and whereas human beings had never before created enough pollution to impact global climate, for the past 250 years it seems they have been doing so with drastic consequences. When added to the current warming trend due to solar activity, the human activity of burning fossil fuels does seem to be exacerbating the situation.

Releasing carbon into the atmosphere through the burning of fossil fuels is not the only way people are helping to contribute to the problem of rising global temperatures. Unsustainable forestry practices such as deforestation, the cutting of trees without replanting them, are also adding to it. Trees play a vital role in the climate of Earth and it is easy for some companies and governments to forget that when they only see them as a means of gathering more income. Not only do trees protect the land and provide a habitat for creatures around them, but they also serve a crucial function in filtering out the carbon dioxide from the atmosphere and producing oxygen as a result. By absorbing the CO2 from the air around them, trees serve a similar function as fossil fuels in that they store up excess carbon inside their trunks and maintain a balance of that gas in the atmosphere. It is estimated that between 1/4 and 1/3 of all carbon emissions attributed to human activity is absorbed and stored by trees as well as other forms of plant life (Reich, 2013). When these natural air filters are cut down and replanted, there can be a balance between forestry and the impact it has on the environment, but in far too many parts of the world, deforestation is out of control and vast expanses of forests that would normally be removing CO2 from the atmosphere are prevented from doing so. Cutting the trees does not directly add CO2 to the atmosphere, but it builds up more because it is not being filtered out and removed.

The failure to replant new trees after logging surely affects the levels of CO2 building up above the Earth, but there is still the matter of what happens to the trees and all the stored carbon they contain from 30 or 50 years of life. When a tree dies a natural death, the carbon it has stored up returns slowly to the soil around it, with minimal amounts returning back into the atmosphere as carbon dioxide. When trees are made into lumber and used for construction of houses or furniture, the carbon of most of the tree still remains inside the wood being used. What makes matters worse for global climate is what happens to many of these trees around the world, especially when they are burned. The easiest way for many subsistence farmers to clear land they wish to convert to agriculture is by burning the entire area to the ground as they lack the machinery to harvest the trees properly. Just as with fossil fuels, this burning releases great amounts of carbon directly into the atmosphere. In many cultures, wood is also burned but for use as fuel or a source of heat, and some areas such as Indonesia and Brazil can release more carbon through this process than the industrialized United States, and globally accounts for 25% of all CO2 emissions compared to 14% by industry (Howden, 2007). When trees are burned, this adds to the problem of deforestation practices as it not only adds CO2 to the atmosphere but prevents it being absorbed and safely stored.

Global warming and climate change on Earth does result from many natural phenomena, mainly the amount and type of energy which is released by the Sun. However, there are also many human activities that are contributing to the problem. Whether or not human activity is responsible for global warming is another discussion entirely, but evidence seems to indicate that what people do on the planet does contribute and perhaps needs to be examined further and far better regulated.

References

Fischer, D. (2011, August 16). Why carbon dioxide is a greenhouse gas. Scientific American. Retrieved from http://www.scientificamerican.com/article.cfm?id=why- carbon-dioxide-is-greenhouse-gas

Howden, D. (2007, May 14). Deforestation: The hidden cause of global warming. Countercurrents.org. Retrieved from http://www.countercurrents.org/howden140507.htm

National Aeronautics and Space Administration (NASA). (n.d.). A blanket around the Earth. Retrieved from http://climate.nasa.gov/causes/

Page, L. (2010, October 7). Much of recent global warming actually caused by Sun. The Register. Retrieved from http://www.theregister.co.uk/2010/10/07/solar_as_big_as_people/

Reich, P. (2013, June 12). How much carbon can the world's forests absorb? Phys.org. Retrieved from http://phys.org/news/2013-06-carbon-world-forests-absorb.html