Global Warming
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Global Warming: Is It Really Happening? Global warming, at least as measured by climate experts, is really happening. Over the last 100 years, it has been estimated that the average global air temperature has risen between 0.3 and 0.6 degree Celsius. Though there is debate over other aspects of global warming, scientists generally agree that global temperatures have risen. However, a big source of disagreement is whether this is a normal or an abnormal warming. Too little is known about long-term global temperature cycles, some say, to determine if this is abnormal. Reliable weather data, it is true, have only been kept for the last century or so (Montague 1). As a result, some question whether there is significant cause for alarm about global warming as a real problem. While I agree that some caution is warranted when predicting the final outcome of this warming trend, I feel that to disregard the problem altogether is extremely shortsighted, because the effects of even a temporary, normal warming trend are potentially devastating for earth and its inhabitants. Most people would agree.
It is in our best interests to know as much as possible about global warming, its causes and potential effects. Before we discuss the true nature of the controversy, let’s look at how global warming works.
Global warming is an increase in average air temperature on earths surface, as measured from many points across the globe. Global warming, in its simplest form, is a product of two factors: so-called greenhouse gases and radiation from our local star, the Sun. The idea is that sunlight enters earths atmosphere, hits molecules of atmospheric gas on earth’s surface, and is converted to other forms of energy such as heat. Sometimes this energy is prevented from escaping back into space by a “blanket” of gases such as carbon dioxide, and a net gain of heat occurs (Britt). Without these gases, our planet would be about 60 degrees Fahrenheit colder than it is today (Montague 1), too cold for many terrestrial life forms that now thrive here. But there is concern that too much heat buildup caused by unnatural levels of so-called greenhouse gases will be dangerous for our planet.
Now that scientists have established that global warming is taking place, the next question is why? Is this, as stated before, a normal trend for our planet? Or is this something that is occurring because of human interference with earths natural systems?
Most likely, our planet does experience warming and cooling cycles, and it is possible that the current warming trend is one of them. However, the normal warming trend may be compounded by human practices that increase atmospheric levels of the four principal greenhouse gases: carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons (CFCs) (Montague 1).
Many of our activities could lead to a buildup of these gases and a resulting increase in global temperatures. Carbon dioxide makes up the majority of the atmospheric gases. Therefore its emission is of the most concern. The greatest source of increase in atmospheric carbon dioxide is suspected to be the burning of fossil fuels such as coal and oil. Since the beginning of the Industrial Age, burning of fossil fuels has increased dramatically, resulting in an increase of atmospheric carbon dioxide of almost 55% (Montague 1). According to current theory, this is a major cause of the current warming trend, and the whole effect of this has yet to be seen. Already, increased temperatures have had many effects, including weather pattern changes, increased rates of glacial melting, subsequent sea-level increases, and air and sea-surface temperature increases, sometimes with resulting shifts in plant and animal species. Models predict that, if current theories hold true, temperatures will rise between 1 and 3.5 degrees Celsius by 2100. Temperature increases are expected to be highest over land, changing climates and affecting habitat suitability for terrestrial species, which may be forced to migrate or become extinct. These temperature increases are also expected to result in a sea-level rise of 15 to 95 cm due to increased glacial melting. This would result in flooding in low-lying coastal regions. Changes in ocean circulation will result in rising local sea temperatures, causing unforeseeable effects for species in these areas. The biggest immediate effect of global warming is changes in weather, especially greater variability in temperatures and precipitation. Extreme seasonal temperatures can contribute to formation of hurricanes and tornados. Hurricanes are encouraged by high air temperatures, which lead to increased water temperatures over the oceans. A current increase in US tornados within the last four decades is thought to be associated with temperature increases, as well. Will global warming lead to mass extinctions, or will species migrate to the cooler poles and adapt to life there? Both are likely, but extinctions are inevitable if, as predicted, global temperature increases continue far into the future.
But even without these continued increases, minor temperature changes can have huge effects on habitats, simultaneously affecting populations of many species. For instance, a long-term study of coastal waters off southern California, conducted by John McGowan and Dean Roemmich of the Scripps Institution of Oceanography, has shown a 2 to 3 degrees Fahrenheit temperature increase in the sea surface temperature in the last fifty years (Svitil36). This has led to density changes in the surface waters, which have had broad implications for the suitability of the habitat for the species living there. Changes in habitat naturally lead to changes in energy resources as species unable to cope with change die out or disperse to other areas. As one population shrinks, other dependent species populations are stressed for food resources, in turn stressing the populations’ dependent upon them. In the study previously mentioned, changes in density stratification of the water altered the amount of chemical nutrients carried up from the bacterial beds in the depths of the ocean. As nutrient levels declined near the surface, plants dependent upon these nutrients suffered declines in population, which in turn reduced populations of plant-dependent phytoplankton. The population-reducing effects moved up the food chain reducing populations, from phytoplankton to zooplankton to fish to seabirds (Svitil 36). Clearly, even minor temperature changes have the capacity to significantly alter population numbers, and, as the scale of climate change increases, extinctions are inevitable.
Alternatively, some say that extinctions due to climate change will be limited because populations will migrate to cooler climates, avoiding the effects of climate change. To a point, I agree. However, rates at which warming