Fundamentals of Global Warming
Climate
Most people can easily identify changes in the weather. A bright, sunny day with a few thin clouds stretched across an otherwise blue sky can change into a cold day of rain and hail by tomorrow. The changes in climate, however, are too small to be detected by the daily weather-watcher. Climate is the average of weather over a long period of time. For example, a region may be typically humid, snowy, rainy or mild. According to the EPA (2004), climate is what you expect, and weather is what you get. Our climate temperature has increased about 1 degree F in the last century, warming at a faster rate over the last two decades.
When we speak about climate, we are speaking about the impact of solar energy. We know that the sun warms the air and that hot air rises. The air brings moisture from the sea, and as the air cools, the moisture condenses to make clouds. Some of the solar energy is re-radiated from Earth and back into space while other energy is trapped within our atmosphere.
The climate system is a link between the atmosphere, oceans, ice sheets, rocks and sediments, and living organisms (Buchdahl, 1999). Nothing within the system operates independently. For instance, the Gulf Stream in the North Atlantic contributes to the warm weather in Western Europe. The stream is like a conveyor belt with warm water on top and cold water on the bottom. The cold water is saltier and sinks to the bottom at five billion gallons per second, pulling the warm water in the opposite direction. As the ice melts, fresh water dilutes the salinity and decreases the amount of water that sinks, halting the conveyor belt flow (Motavalli, 2004). The last time the Gulf Stream ceased to flow, about 10,000 years ago, Europe endured an ice age that lasted about 1,000 years (Gore, 2006).
Climate models show that global warming produces extremes in temperatures, so not only do summers become hotter, but winters become colder. Global warming can actually cause an Ice Age in some regions. With this in mind, it is important to remember that climate change is not about bad weather changing into a nice day, or even about finding relief after a long summer with the long-awaited cool temperatures of autumn. Climate change is about altering temperatures for hundreds or thousands of years.
Atmosphere
If we could strip Venus and Earth of their atmospheres and place them side by side, we might notice some similarities. They have the same origin, they are similar sizes, and they share a similar distance from the sun. Even as we add the primitive atmosphere of both planets, we notice what they have in common. Both atmospheres originally contained hydrogen, helium, methane, ammonia, nitrogen, neon, and a small amount of argon. A major difference between the two planets occurs when we note that Earth's original atmosphere has escaped. Our current atmosphere is influenced by volcanic eruptions, which contain large amounts of nitrogen, carbon dioxide, and water vapor.
The atmospheres of Venus and Earth both contain carbon dioxide. Fortunately, the rocks of our own planet were able to absorb a great deal of CO 2, whereas the rocks on Venus were never cool enough to do so. Venus has always been slightly hotter than Earth. The principles of CO 2, however, remain the same on both planets.
CO 2 is a greenhouse gas, along with water vapor, methane, nitrous oxide, ozone, halogenated fluorocarbons, perfluoronated carbons, and hydrofluoronated carbons. To understand the affect of greenhouse gases, we can imagine walking into a greenhouse full of plants. Here, we can look through the transparent glass and see the sun and everything else outside of the greenhouse, and we can feel the heat that is trapped inside. It is true that we need greenhouse gases to sustain life. Of course, an extreme excess of such gases would create an uninhabitable planet, perhaps one that resembled Venus a bit more closely. Without its current greenhouse effect, the average climate of Venus would be a balmy 20 degrees C (70 F) instead of the actual temperature of 400 C (750 F). Earth, in turn, would be -25 C without the greenhouse effect. In order for a planet to be habitable, the temperature must be between 0 and 100 degrees C. A healthy greenhouse balance gives Earth's climate an average temperature of 10 C (50 F).
The greenhouse effect acts as a kind of gateway for the sun's radiation. The high-energy short waves of radiation come from the sun and pass through our atmosphere. Earth re-radiates the absorbed portion of this energy back toward space as infrared radiation, or heat, but the greenhouse gases trap most of these long, low-energy waves in our atmosphere. This is why we can see visible light pass through the glass of a greenhouse while the heat stays inside. The windows in our homes also let in visible light in while trapping infrared radiation. If they didn't, we'd have to seal up all of our windows during the winter.
Not all of the radiation makes it close enough to the surface to become re-radiated heat. Some of the radiation is reflected back into space by clouds and ice. This reflectivity is known as albedo. Fashion experts have an intrinsic understanding of albedo - after all, this is why people wear white (or light-colored) clothes in the summer and black (or dark-colored) clothes in the winter. While the white shirt reflects the radiation from the sun and keeps us cooler, the black shirt absorbs the radiation and keeps us warmer.
About 39 % of radiation is reflected (the albedo is 0.39), while the remaining 61 % is absorbed by the surface and emitted as infrared radiation. With an albedo of 0, our planet would be a perfect black body. In other words, Earth would absorb all of the radiation and reflect absolutely nothing. Our albedo depends on clouds, snow and ice. The problem with clouds is that while they contribute to the planet's albedo, they also contribute to warming the planet. Clouds trap infrared radiation. As the planet warms, water evaporates and forms clouds that decrease absorption of solar energy. On the other hand, as the planet warms, the ice melts, increasing the absorption of solar energy. As the ice melts, the albedo decreases. As the albedo decreases, the planet warms. As the planet warms, the ice continues to melt. This is part of the cycle we know as global warming.
Fossil Fuels
CO 2, a greenhouse gas that traps heat, increases as our growing population depends more and more on the use of fossil fuels to run our machines. Not only is CO 2 increasing, it is increasing exponentially. This is the difference between 10 x 2 and 10 raised to the 2 nd power. CO 2 is a waste product of fossil fuels such as coal, petroleum and gas (Flannery, 2005). We rely on the remains of decomposed plants and animals to generate electricity, heat our homes, and provide transportation. It is difficult to imagine a life without fossil fuels, but to continue as we are will turn short-term gratification into long-term devastation.
So far, we have relied on oceans and trees to absorb our CO 2 emissions. Tim Flannery, author of The Weather Makers (2005), describes the problem occurring with our oceans today. The North Atlantic, he writes, contains almost a quarter of the carbon we've emitted, while it only constitutes 15 % of the ocean's surface. He also notes that as the ocean warms, it has less ability to absorb CO 2, much like a warm carbonated drink falls flat. The oceans also become more acidic as they take in more CO 2. The more acidic they become, the less CO 2 they can absorb.
Trees absorb CO 2 through photosynthesis. However, as forests are burned, more CO 2 is released into the air. This also occurs as trees die and decompose. Planting more trees is certainly better than burning them or cutting them down to rot, but this action will not resolve the long-term problem. While trees temporarily absorb CO 2, they unfortunately decrease the albedo.
CO 2 levels will double; it is not a matter of whether they will or won't, but a matter of when. If we take action now to decrease our use of fossil fuels, and therefore decrease the amount of CO 2 that we release into our atmosphere, the levels will double in two centuries. If we do nothing at all, the CO 2 levels will double in forty years.
Consequences
While some of us may think of warmer temperatures as not having to scrape so much ice off our windshields, we must come to terms with the destructive ramifications to our planet as a whole. We must also remember that we are not talking about a few days of milder weather during winter, but about a major climatic shift that will considerably alter the planet in ways that span beyond our lifetime. It may be easy for certain members (and leaders) of our society to shrug apathetically when asked to consider the world we are leaving the children in our classrooms today, but as educators, we cannot afford such self-centered thinking.
To put it simply, the icecaps are melting, polar bears are drowning, people who depend on the ice are already struggling to maintain their lives, and animals are becoming extinct. We face rising sea levels, an increase in storms, and a change in rain distribution that could destroy the crops of Middle America along with other food-sources around the world. We are coming to a time when floods will displace large populations; survivors will migrate to drier areas while others drown or die from diseases that were once foreign to their homelands. Perhaps SUVs, like cockroaches, will persist, trampling over muddy lands where magnificent glaciers once stood.
It is overwhelming. It is also difficult to believe, especially when I can look out my window over high desert Santa Fe and see that the mountains are as brown as they ever were, or that the rain that never comes finally came days ago and is still splashing tufts of yellow grass into a bright shade of green. However, there is evidence today of the effects of global warming. Elizabeth Kolbert, author of Field Notes from a Catastrophe (2006), describes the gradual extinction of the golden toad due to climate change, the migration of birds and butterflies as temperatures increase, the thawing of permafrost just below the Arctic Circle, the acidity of oceans, the disappearance of sea ice, and the unavoidable relocation of villages due to melting ice and an increase of storms brought on by warmer weather. With all that we know, how is it possible to deny the existence of global warming?
Controversy
There are uncertainties. Scientists know that human activity is increasing the level of greenhouse gases, but they do not know where the increase will stop. They know that global temperatures will continue to rise, but it is not clear whether the increase will be 1.4 or 5.8 degrees C, or somewhere in between. They know that warm water causes an increase in hurricanes, but it is not possible to tell if specific hurricanes today are due to global warming. They know that the sea levels will rise, but they don't know exactly how high. Although scientists know that global warming will impact wildlife, natural resources and human health, they cannot predict the exact outcome, especially when looking at specific local regions (EPA, 2002).
However, there is no doubt among scientists that global warming exists, and that human activity is mostly responsible. Scientists use ice core samples and trapped air bubbles in amber to determine the atmosphere of our past, allowing comparative measurements to be made today. CO 2 measurements are made in the troposphere above a mountain in Hawaii, where the atmosphere is less contaminated. Scientific data gives us a low number and a high number insofar as possible outcomes. Even the lowest projected global temperature rise of 1.4 C by 2100 is a greater rise than seen in the last 10,000 years, according to the IPCC (EPA, 2002). There are degrees of uncertainty within each projection, but all scientific projections show some degree of global warming.
Some of the uncertainty involves the use of climate models. By their nature, climate models must simplify data. They are tested to determine past climate changes, and they are useful as estimation tools. Different researchers use different models to test different sets of data, and therefore create different results. Gradually, the climate models are beginning to converge, but for now they produce uncertainties. Something worth noting is that published scientific sources will include room for probable error. These are not mistakes; they are uncertainties. If a source does not include uncertainties, but insists that, say, oceans will rise 80 feet, it is probably not a valid scientific source.
An uncertainty about to what degree global warming occurs or what impact it will have is not the same as questioning whether global warming occurs or if it will have any impact at all. This would be like not knowing what a friend had for lunch today and therefore arriving at the conclusion that this friend never eats lunch.
Uncertainties are sometimes used by non-scientists to confuse and mislead the public. According to some of our policy makers, there is too much confusion about whether our friend had a sandwich or bowl of soup, so that means our friend never eats lunch and never will, and global warming does not exist. On the other hand, it is just as unrealistic to assume that our friend will explode from too much food. It is useless and incorrect to say that we are doomed.
Mitigation
One of the drawbacks of being aware of the world around us is that it becomes difficult to live life as usual. We may think about CO 2 levels as we fill our car with gas or drive by a power plant, but how can we turn our thoughts into actions - or even feel confident that our actions even make the tiniest dent in global warming?
On an international level, the Kyoto Protocol, an amendment to the United Nations Framework Convention on Climate Change (UNFCCC), is an effort to mitigate the anthropogenic, or human created, greenhouse gases. Countries must commit to reducing their emissions of CO 2 and other greenhouse gases or engage in emissions trading. Countries that exceed the allotted emissions would have to buy emission credits from a country that stays below the set limitations.
Scientists have also considered renewable energy resources such as windmills, hydroelectric power, solar power, or nuclear power. Unfortunately, windmills require steady wind to work consistently, hydroelectric power involves risks in damming and redirecting waters, solar panels need reliable sunlight, and nuclear power produces nuclear waste. It is also difficult to transport wind, hydro and solar power over long distances. However, current development of renewable energy resources for large and small areas will help reduce our emissions of greenhouse gases.
As individuals, we have plenty of opportunities to do our small part. For instance, we can drive something other than SUVs. At home, we can use compact fluorescent lights rather than incandescent bulbs, as the latter bulb wastes more energy as heat and does not last as long as a compact fluorescent light. We can keep our thermostat slightly cooler in winter and warmer in summer in order to save energy, and reduce the amount of electricity and gas we use in general. Students and teachers can find more suggestions in the back of An Inconvenient Truth by Al Gore and in renewable energy books such as Smart Power by William H. Kemp. In fact, some students may find it interesting to pursue renewable energy resources as the focus of their research.
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